--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/components/gcc3/g77.1 Wed May 18 20:49:57 2011 -0700
@@ -0,0 +1,1735 @@
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+.rm #[ #] #H #V #F C
+.\" ========================================================================
+.\"
+.IX Title "G77 1"
+.TH G77 1 "2004-11-05" "gcc-3.4.3" "GNU"
+.SH "NAME"
+g77 \- GNU project Fortran 77 compiler
+.SH "SYNOPSIS"
+.IX Header "SYNOPSIS"
+g77 [\fB\-c\fR|\fB\-S\fR|\fB\-E\fR]
+ [\fB\-g\fR] [\fB\-pg\fR] [\fB\-O\fR\fIlevel\fR]
+ [\fB\-W\fR\fIwarn\fR...] [\fB\-pedantic\fR]
+ [\fB\-I\fR\fIdir\fR...] [\fB\-L\fR\fIdir\fR...]
+ [\fB\-D\fR\fImacro\fR[=\fIdefn\fR]...] [\fB\-U\fR\fImacro\fR]
+ [\fB\-f\fR\fIoption\fR...] [\fB\-m\fR\fImachine-option\fR...]
+ [\fB\-o\fR \fIoutfile\fR] \fIinfile\fR...
+.PP
+Only the most useful options are listed here; see below for the
+remainder.
+.SH "DESCRIPTION"
+.IX Header "DESCRIPTION"
+The \fBg77\fR command supports all the options supported by the
+\&\fBgcc\fR command.
+.PP
+All \fBgcc\fR and \fBg77\fR options
+are accepted both by \fBg77\fR and by \fBgcc\fR
+(as well as any other drivers built at the same time,
+such as \fBg++\fR),
+since adding \fBg77\fR to the \fBgcc\fR distribution
+enables acceptance of \fBg77\fR options
+by all of the relevant drivers.
+.PP
+In some cases, options have positive and negative forms;
+the negative form of \fB\-ffoo\fR would be \fB\-fno\-foo\fR.
+This manual documents only one of these two forms, whichever
+one is not the default.
+.SH "OPTIONS"
+.IX Header "OPTIONS"
+Here is a summary of all the options specific to \s-1GNU\s0 Fortran, grouped
+by type. Explanations are in the following sections.
+.IP "\fIOverall Options\fR" 4
+.IX Item "Overall Options"
+\&\fB\-fversion \-fset\-g77\-defaults \-fno\-silent\fR
+.IP "\fIShorthand Options\fR" 4
+.IX Item "Shorthand Options"
+\&\fB\-ff66 \-fno\-f66 \-ff77 \-fno\-f77 \-fno\-ugly\fR
+.IP "\fIFortran Language Options\fR" 4
+.IX Item "Fortran Language Options"
+\&\fB\-ffree\-form \-fno\-fixed\-form \-ff90
+\&\-fvxt \-fdollar\-ok \-fno\-backslash
+\&\-fno\-ugly\-args \-fno\-ugly\-assign \-fno\-ugly\-assumed
+\&\-fugly\-comma \-fugly\-complex \-fugly\-init \-fugly\-logint
+\&\-fonetrip \-ftypeless\-boz
+\&\-fintrin\-case\-initcap \-fintrin\-case\-upper
+\&\-fintrin\-case\-lower \-fintrin\-case\-any
+\&\-fmatch\-case\-initcap \-fmatch\-case\-upper
+\&\-fmatch\-case\-lower \-fmatch\-case\-any
+\&\-fsource\-case\-upper \-fsource\-case\-lower
+\&\-fsource\-case\-preserve
+\&\-fsymbol\-case\-initcap \-fsymbol\-case\-upper
+\&\-fsymbol\-case\-lower \-fsymbol\-case\-any
+\&\-fcase\-strict\-upper \-fcase\-strict\-lower
+\&\-fcase\-initcap \-fcase\-upper \-fcase\-lower \-fcase\-preserve
+\&\-ff2c\-intrinsics\-delete \-ff2c\-intrinsics\-hide
+\&\-ff2c\-intrinsics\-disable \-ff2c\-intrinsics\-enable
+\&\-fbadu77\-intrinsics\-delete \-fbadu77\-intrinsics\-hide
+\&\-fbadu77\-intrinsics\-disable \-fbadu77\-intrinsics\-enable
+\&\-ff90\-intrinsics\-delete \-ff90\-intrinsics\-hide
+\&\-ff90\-intrinsics\-disable \-ff90\-intrinsics\-enable
+\&\-fgnu\-intrinsics\-delete \-fgnu\-intrinsics\-hide
+\&\-fgnu\-intrinsics\-disable \-fgnu\-intrinsics\-enable
+\&\-fmil\-intrinsics\-delete \-fmil\-intrinsics\-hide
+\&\-fmil\-intrinsics\-disable \-fmil\-intrinsics\-enable
+\&\-funix\-intrinsics\-delete \-funix\-intrinsics\-hide
+\&\-funix\-intrinsics\-disable \-funix\-intrinsics\-enable
+\&\-fvxt\-intrinsics\-delete \-fvxt\-intrinsics\-hide
+\&\-fvxt\-intrinsics\-disable \-fvxt\-intrinsics\-enable
+\&\-ffixed\-line\-length\-\fR\fIn\fR \fB\-ffixed\-line\-length\-none\fR
+.IP "\fIWarning Options\fR" 4
+.IX Item "Warning Options"
+\&\fB\-fsyntax\-only \-pedantic \-pedantic\-errors \-fpedantic
+\&\-w \-Wno\-globals \-Wimplicit \-Wunused \-Wuninitialized
+\&\-Wall \-Wsurprising
+\&\-Werror \-W\fR
+.IP "\fIDebugging Options\fR" 4
+.IX Item "Debugging Options"
+\&\fB\-g\fR
+.IP "\fIOptimization Options\fR" 4
+.IX Item "Optimization Options"
+\&\fB\-malign\-double
+\&\-ffloat\-store \-fforce\-mem \-fforce\-addr \-fno\-inline
+\&\-ffast\-math \-fstrength\-reduce \-frerun\-cse\-after\-loop
+\&\-funsafe\-math\-optimizations \-ffinite\-math\-only \-fno\-trapping\-math
+\&\-fexpensive\-optimizations \-fdelayed\-branch
+\&\-fschedule\-insns \-fschedule\-insn2 \-fcaller\-saves
+\&\-funroll\-loops \-funroll\-all\-loops
+\&\-fno\-move\-all\-movables \-fno\-reduce\-all\-givs
+\&\-fno\-rerun\-loop\-opt\fR
+.IP "\fIDirectory Options\fR" 4
+.IX Item "Directory Options"
+\&\fB\-I\fR\fIdir\fR \fB\-I\-\fR
+.IP "\fICode Generation Options\fR" 4
+.IX Item "Code Generation Options"
+\&\fB\-fno\-automatic \-finit\-local\-zero \-fno\-f2c
+\&\-ff2c\-library \-fno\-underscoring \-fno\-ident
+\&\-fpcc\-struct\-return \-freg\-struct\-return
+\&\-fshort\-double \-fno\-common \-fpack\-struct
+\&\-fzeros \-fno\-second\-underscore
+\&\-femulate\-complex
+\&\-falias\-check \-fargument\-alias
+\&\-fargument\-noalias \-fno\-argument\-noalias\-global
+\&\-fno\-globals \-fflatten\-arrays
+\&\-fbounds\-check \-ffortran\-bounds\-check\fR
+.PP
+Compilation can involve as many as four stages: preprocessing, code
+generation (often what is really meant by the term ``compilation''),
+assembly, and linking, always in that order. The first three
+stages apply to an individual source file, and end by producing an
+object file; linking combines all the object files (those newly
+compiled, and those specified as input) into an executable file.
+.PP
+For any given input file, the file name suffix determines what kind of
+program is contained in the file\-\-\-that is, the language in which the
+program is written is generally indicated by the suffix.
+Suffixes specific to \s-1GNU\s0 Fortran are listed below.
+.IP "\fIfile\fR\fB.f\fR" 4
+.IX Item "file.f"
+.PD 0
+.IP "\fIfile\fR\fB.for\fR" 4
+.IX Item "file.for"
+.IP "\fIfile\fR\fB.FOR\fR" 4
+.IX Item "file.FOR"
+.PD
+Fortran source code that should not be preprocessed.
+.Sp
+Such source code cannot contain any preprocessor directives, such
+as \f(CW\*(C`#include\*(C'\fR, \f(CW\*(C`#define\*(C'\fR, \f(CW\*(C`#if\*(C'\fR, and so on.
+.Sp
+You can force \fB.f\fR files to be preprocessed by \fBcpp\fR by using
+\&\fB\-x f77\-cpp\-input\fR.
+.IP "\fIfile\fR\fB.F\fR" 4
+.IX Item "file.F"
+.PD 0
+.IP "\fIfile\fR\fB.fpp\fR" 4
+.IX Item "file.fpp"
+.IP "\fIfile\fR\fB.FPP\fR" 4
+.IX Item "file.FPP"
+.PD
+Fortran source code that must be preprocessed (by the C preprocessor
+\&\fBcpp\fR, which is part of \s-1GCC\s0).
+.Sp
+Note that preprocessing is not extended to the contents of
+files included by the \f(CW\*(C`INCLUDE\*(C'\fR directive\-\-\-the \f(CW\*(C`#include\*(C'\fR
+preprocessor directive must be used instead.
+.IP "\fIfile\fR\fB.r\fR" 4
+.IX Item "file.r"
+Ratfor source code, which must be preprocessed by the \fBratfor\fR
+command, which is available separately (as it is not yet part of the \s-1GNU\s0
+Fortran distribution).
+A public domain version in C is at
+<\fBhttp://sepwww.stanford.edu/sep/prof/ratfor.shar.2\fR>.
+.PP
+\&\s-1UNIX\s0 users typically use the \fI\fIfile\fI.f\fR and \fI\fIfile\fI.F\fR
+nomenclature.
+Users of other operating systems, especially those that cannot
+distinguish upper-case
+letters from lower-case letters in their file names, typically use
+the \fI\fIfile\fI.for\fR and \fI\fIfile\fI.fpp\fR nomenclature.
+.PP
+Use of the preprocessor \fBcpp\fR allows use of C\-like
+constructs such as \f(CW\*(C`#define\*(C'\fR and \f(CW\*(C`#include\*(C'\fR, but can
+lead to unexpected, even mistaken, results due to Fortran's source file
+format.
+It is recommended that use of the C preprocessor
+be limited to \f(CW\*(C`#include\*(C'\fR and, in
+conjunction with \f(CW\*(C`#define\*(C'\fR, only \f(CW\*(C`#if\*(C'\fR and related directives,
+thus avoiding in-line macro expansion entirely.
+This recommendation applies especially
+when using the traditional fixed source form.
+With free source form,
+fewer unexpected transformations are likely to happen, but use of
+constructs such as Hollerith and character constants can nevertheless
+present problems, especially when these are continued across multiple
+source lines.
+These problems result, primarily, from differences between the way
+such constants are interpreted by the C preprocessor and by a Fortran
+compiler.
+.PP
+Another example of a problem that results from using the C preprocessor
+is that a Fortran comment line that happens to contain any
+characters ``interesting'' to the C preprocessor,
+such as a backslash at the end of the line,
+is not recognized by the preprocessor as a comment line,
+so instead of being passed through ``raw'',
+the line is edited according to the rules for the preprocessor.
+For example, the backslash at the end of the line is removed,
+along with the subsequent newline, resulting in the next
+line being effectively commented out\-\-\-unfortunate if that
+line is a non-comment line of important code!
+.PP
+\&\fINote:\fR The \fB\-traditional\fR and \fB\-undef\fR flags are supplied
+to \fBcpp\fR by default, to help avoid unpleasant surprises.
+.PP
+This means that \s-1ANSI\s0 C preprocessor features (such as the \fB#\fR
+operator) aren't available, and only variables in the C reserved
+namespace (generally, names with a leading underscore) are liable to
+substitution by C predefines.
+Thus, if you want to do system-specific
+tests, use, for example, \fB#ifdef _\|_linux_\|_\fR rather than \fB#ifdef linux\fR.
+Use the \fB\-v\fR option to see exactly how the preprocessor is invoked.
+.PP
+Unfortunately, the \fB\-traditional\fR flag will not avoid an error from
+anything that \fBcpp\fR sees as an unterminated C comment, such as:
+.PP
+.Vb 2
+\& C Some Fortran compilers accept /* as starting
+\& C an inline comment.
+.Ve
+.PP
+The following options that affect overall processing are recognized
+by the \fBg77\fR and \fBgcc\fR commands in a \s-1GNU\s0 Fortran installation:
+.IP "\fB\-fversion\fR" 4
+.IX Item "-fversion"
+Ensure that the \fBg77\fR version of the compiler phase is reported,
+if run,
+and, starting in \f(CW\*(C`egcs\*(C'\fR version 1.1,
+that internal consistency checks in the \fIf771\fR program are run.
+.Sp
+This option is supplied automatically when \fB\-v\fR or \fB\-\-verbose\fR
+is specified as a command-line option for \fBg77\fR or \fBgcc\fR
+and when the resulting commands compile Fortran source files.
+.Sp
+In \s-1GCC\s0 3.1, this is changed back to the behavior \fBgcc\fR displays
+for \fB.c\fR files.
+.IP "\fB\-fset\-g77\-defaults\fR" 4
+.IX Item "-fset-g77-defaults"
+\&\fIVersion info:\fR
+This option was obsolete as of \f(CW\*(C`egcs\*(C'\fR
+version 1.1.
+The effect is instead achieved
+by the \f(CW\*(C`lang_init_options\*(C'\fR routine
+in \fIgcc/gcc/f/com.c\fR.
+.Sp
+Set up whatever \fBgcc\fR options are to apply to Fortran
+compilations, and avoid running internal consistency checks
+that might take some time.
+.Sp
+This option is supplied automatically when compiling Fortran code
+via the \fBg77\fR or \fBgcc\fR command.
+The description of this option is provided so that users seeing
+it in the output of, say, \fBg77 \-v\fR understand why it is
+there.
+.Sp
+Also, developers who run \f(CW\*(C`f771\*(C'\fR directly might want to specify it
+by hand to get the same defaults as they would running \f(CW\*(C`f771\*(C'\fR
+via \fBg77\fR or \fBgcc\fR
+However, such developers should, after linking a new \f(CW\*(C`f771\*(C'\fR
+executable, invoke it without this option once,
+e.g. via \f(CW\*(C`./f771 \-quiet < /dev/null\*(C'\fR,
+to ensure that they have not introduced any
+internal inconsistencies (such as in the table of
+intrinsics) before proceeding\-\-\-\fBg77\fR will crash
+with a diagnostic if it detects an inconsistency.
+.IP "\fB\-fno\-silent\fR" 4
+.IX Item "-fno-silent"
+Print (to \f(CW\*(C`stderr\*(C'\fR) the names of the program units as
+they are compiled, in a form similar to that used by popular
+\&\s-1UNIX\s0 \fBf77\fR implementations and \fBf2c\fR
+.Sh "Shorthand Options"
+.IX Subsection "Shorthand Options"
+The following options serve as ``shorthand''
+for other options accepted by the compiler:
+.IP "\fB\-fugly\fR" 4
+.IX Item "-fugly"
+\&\fINote:\fR This option is no longer supported.
+The information, below, is provided to aid
+in the conversion of old scripts.
+.Sp
+Specify that certain ``ugly'' constructs are to be quietly accepted.
+Same as:
+.Sp
+.Vb 3
+\& -fugly-args -fugly-assign -fugly-assumed
+\& -fugly-comma -fugly-complex -fugly-init
+\& -fugly-logint
+.Ve
+.Sp
+These constructs are considered inappropriate to use in new
+or well-maintained portable Fortran code, but widely used
+in old code.
+.IP "\fB\-fno\-ugly\fR" 4
+.IX Item "-fno-ugly"
+Specify that all ``ugly'' constructs are to be noisily rejected.
+Same as:
+.Sp
+.Vb 3
+\& -fno-ugly-args -fno-ugly-assign -fno-ugly-assumed
+\& -fno-ugly-comma -fno-ugly-complex -fno-ugly-init
+\& -fno-ugly-logint
+.Ve
+.IP "\fB\-ff66\fR" 4
+.IX Item "-ff66"
+Specify that the program is written in idiomatic \s-1FORTRAN\s0 66.
+Same as \fB\-fonetrip \-fugly\-assumed\fR.
+.Sp
+The \fB\-fno\-f66\fR option is the inverse of \fB\-ff66\fR.
+As such, it is the same as \fB\-fno\-onetrip \-fno\-ugly\-assumed\fR.
+.Sp
+The meaning of this option is likely to be refined as future
+versions of \fBg77\fR provide more compatibility with other
+existing and obsolete Fortran implementations.
+.IP "\fB\-ff77\fR" 4
+.IX Item "-ff77"
+Specify that the program is written in idiomatic \s-1UNIX\s0 \s-1FORTRAN\s0 77
+and/or the dialect accepted by the \fBf2c\fR product.
+Same as \fB\-fbackslash \-fno\-typeless\-boz\fR.
+.Sp
+The meaning of this option is likely to be refined as future
+versions of \fBg77\fR provide more compatibility with other
+existing and obsolete Fortran implementations.
+.IP "\fB\-fno\-f77\fR" 4
+.IX Item "-fno-f77"
+The \fB\-fno\-f77\fR option is \fInot\fR the inverse
+of \fB\-ff77\fR.
+It specifies that the program is not written in idiomatic \s-1UNIX\s0
+\&\s-1FORTRAN\s0 77 or \fBf2c\fR but in a more widely portable dialect.
+\&\fB\-fno\-f77\fR is the same as \fB\-fno\-backslash\fR.
+.Sp
+The meaning of this option is likely to be refined as future
+versions of \fBg77\fR provide more compatibility with other
+existing and obsolete Fortran implementations.
+.Sh "Options Controlling Fortran Dialect"
+.IX Subsection "Options Controlling Fortran Dialect"
+The following options control the dialect of Fortran
+that the compiler accepts:
+.IP "\fB\-ffree\-form\fR" 4
+.IX Item "-ffree-form"
+.PD 0
+.IP "\fB\-fno\-fixed\-form\fR" 4
+.IX Item "-fno-fixed-form"
+.PD
+Specify that the source file is written in free form
+(introduced in Fortran 90) instead of the more-traditional fixed form.
+.IP "\fB\-ff90\fR" 4
+.IX Item "-ff90"
+Allow certain Fortran\-90 constructs.
+.Sp
+This option controls whether certain
+Fortran 90 constructs are recognized.
+(Other Fortran 90 constructs
+might or might not be recognized depending on other options such as
+\&\fB\-fvxt\fR, \fB\-ff90\-intrinsics\-enable\fR, and the
+current level of support for Fortran 90.)
+.IP "\fB\-fvxt\fR" 4
+.IX Item "-fvxt"
+Specify the treatment of certain constructs that have different
+meanings depending on whether the code is written in
+\&\s-1GNU\s0 Fortran (based on \s-1FORTRAN\s0 77 and akin to Fortran 90)
+or \s-1VXT\s0 Fortran (more like \s-1VAX\s0 \s-1FORTRAN\s0).
+.Sp
+The default is \fB\-fno\-vxt\fR.
+\&\fB\-fvxt\fR specifies that the \s-1VXT\s0 Fortran interpretations
+for those constructs are to be chosen.
+.IP "\fB\-fdollar\-ok\fR" 4
+.IX Item "-fdollar-ok"
+Allow \fB$\fR as a valid character in a symbol name.
+.IP "\fB\-fno\-backslash\fR" 4
+.IX Item "-fno-backslash"
+Specify that \fB\e\fR is not to be specially interpreted in character
+and Hollerith constants a la C and many \s-1UNIX\s0 Fortran compilers.
+.Sp
+For example, with \fB\-fbackslash\fR in effect, \fBA\enB\fR specifies
+three characters, with the second one being newline.
+With \fB\-fno\-backslash\fR, it specifies four characters,
+\&\fBA\fR, \fB\e\fR, \fBn\fR, and \fBB\fR.
+.Sp
+Note that \fBg77\fR implements a fairly general form of backslash
+processing that is incompatible with the narrower forms supported
+by some other compilers.
+For example, \fB'A\e003B'\fR is a three-character string in \fBg77\fR
+whereas other compilers that support backslash might not support
+the three-octal-digit form, and thus treat that string as longer
+than three characters.
+.IP "\fB\-fno\-ugly\-args\fR" 4
+.IX Item "-fno-ugly-args"
+Disallow passing Hollerith and typeless constants as actual
+arguments (for example, \fB\s-1CALL\s0 \s-1FOO\s0(4HABCD)\fR).
+.IP "\fB\-fugly\-assign\fR" 4
+.IX Item "-fugly-assign"
+Use the same storage for a given variable regardless of
+whether it is used to hold an assigned-statement label
+(as in \fB\s-1ASSIGN\s0 10 \s-1TO\s0 I\fR) or used to hold numeric data
+(as in \fBI = 3\fR).
+.IP "\fB\-fugly\-assumed\fR" 4
+.IX Item "-fugly-assumed"
+Assume any dummy array with a final dimension specified as \fB1\fR
+is really an assumed-size array, as if \fB*\fR had been specified
+for the final dimension instead of \fB1\fR.
+.Sp
+For example, \fB\s-1DIMENSION\s0 X(1)\fR is treated as if it
+had read \fB\s-1DIMENSION\s0 X(*)\fR.
+.IP "\fB\-fugly\-comma\fR" 4
+.IX Item "-fugly-comma"
+In an external-procedure invocation,
+treat a trailing comma in the argument list
+as specification of a trailing null argument,
+and treat an empty argument list
+as specification of a single null argument.
+.Sp
+For example, \fB\s-1CALL\s0 \s-1FOO\s0(,)\fR is treated as
+\&\fB\s-1CALL\s0 \s-1FOO\s0(%\f(BIVAL\fB\|(0), %\f(BIVAL\fB\|(0))\fR.
+That is, \fItwo\fR null arguments are specified
+by the procedure call when \fB\-fugly\-comma\fR is in force.
+And \fBF = \s-1\f(BIFUNC\s0()\fB\fR is treated as \fBF = \s-1FUNC\s0(%\f(BIVAL\fB\|(0))\fR.
+.Sp
+The default behavior, \fB\-fno\-ugly\-comma\fR, is to ignore
+a single trailing comma in an argument list.
+So, by default, \fB\s-1CALL\s0 \s-1FOO\s0(X,)\fR is treated
+exactly the same as \fB\s-1CALL\s0 \s-1FOO\s0(X)\fR.
+.IP "\fB\-fugly\-complex\fR" 4
+.IX Item "-fugly-complex"
+Do not complain about \fB\s-1REAL\s0(\fR\fIexpr\fR\fB)\fR or
+\&\fB\s-1AIMAG\s0(\fR\fIexpr\fR\fB)\fR when \fIexpr\fR is a \f(CW\*(C`COMPLEX\*(C'\fR
+type other than \f(CW\*(C`COMPLEX(KIND=1)\*(C'\fR\-\-\-usually
+this is used to permit \f(CW\*(C`COMPLEX(KIND=2)\*(C'\fR
+(\f(CW\*(C`DOUBLE COMPLEX\*(C'\fR) operands.
+.Sp
+The \fB\-ff90\fR option controls the interpretation
+of this construct.
+.IP "\fB\-fno\-ugly\-init\fR" 4
+.IX Item "-fno-ugly-init"
+Disallow use of Hollerith and typeless constants as initial
+values (in \f(CW\*(C`PARAMETER\*(C'\fR and \f(CW\*(C`DATA\*(C'\fR statements), and
+use of character constants to
+initialize numeric types and vice versa.
+.Sp
+For example, \fB\s-1DATA\s0 I/'F'/, \s-1CHRVAR/65/\s0, J/4HABCD/\fR is disallowed by
+\&\fB\-fno\-ugly\-init\fR.
+.IP "\fB\-fugly\-logint\fR" 4
+.IX Item "-fugly-logint"
+Treat \f(CW\*(C`INTEGER\*(C'\fR and \f(CW\*(C`LOGICAL\*(C'\fR variables and
+expressions as potential stand-ins for each other.
+.Sp
+For example, automatic conversion between \f(CW\*(C`INTEGER\*(C'\fR and
+\&\f(CW\*(C`LOGICAL\*(C'\fR is enabled, for many contexts, via this option.
+.IP "\fB\-fonetrip\fR" 4
+.IX Item "-fonetrip"
+Executable iterative \f(CW\*(C`DO\*(C'\fR loops are to be executed at
+least once each time they are reached.
+.Sp
+\&\s-1ANSI\s0 \s-1FORTRAN\s0 77 and more recent versions of the Fortran standard
+specify that the body of an iterative \f(CW\*(C`DO\*(C'\fR loop is not executed
+if the number of iterations calculated from the parameters of the
+loop is less than 1.
+(For example, \fB\s-1DO\s0 10 I = 1, 0\fR.)
+Such a loop is called a \fIzero-trip loop\fR.
+.Sp
+Prior to \s-1ANSI\s0 \s-1FORTRAN\s0 77, many compilers implemented \f(CW\*(C`DO\*(C'\fR loops
+such that the body of a loop would be executed at least once, even
+if the iteration count was zero.
+Fortran code written assuming this behavior is said to require
+\&\fIone-trip loops\fR.
+For example, some code written to the \s-1FORTRAN\s0 66 standard
+expects this behavior from its \f(CW\*(C`DO\*(C'\fR loops, although that
+standard did not specify this behavior.
+.Sp
+The \fB\-fonetrip\fR option specifies that the source file(s) being
+compiled require one-trip loops.
+.Sp
+This option affects only those loops specified by the (iterative) \f(CW\*(C`DO\*(C'\fR
+statement and by implied\-\f(CW\*(C`DO\*(C'\fR lists in I/O statements.
+Loops specified by implied\-\f(CW\*(C`DO\*(C'\fR lists in \f(CW\*(C`DATA\*(C'\fR and
+specification (non\-executable) statements are not affected.
+.IP "\fB\-ftypeless\-boz\fR" 4
+.IX Item "-ftypeless-boz"
+Specifies that prefix-radix non-decimal constants, such as
+\&\fBZ'\s-1ABCD\s0'\fR, are typeless instead of \f(CW\*(C`INTEGER(KIND=1)\*(C'\fR.
+.Sp
+You can test for yourself whether a particular compiler treats
+the prefix form as \f(CW\*(C`INTEGER(KIND=1)\*(C'\fR or typeless by running the
+following program:
+.Sp
+.Vb 6
+\& EQUIVALENCE (I, R)
+\& R = Z'ABCD1234'
+\& J = Z'ABCD1234'
+\& IF (J .EQ. I) PRINT *, 'Prefix form is TYPELESS'
+\& IF (J .NE. I) PRINT *, 'Prefix form is INTEGER'
+\& END
+.Ve
+.Sp
+Reports indicate that many compilers process this form as
+\&\f(CW\*(C`INTEGER(KIND=1)\*(C'\fR, though a few as typeless, and at least one
+based on a command-line option specifying some kind of
+compatibility.
+.IP "\fB\-fintrin\-case\-initcap\fR" 4
+.IX Item "-fintrin-case-initcap"
+.PD 0
+.IP "\fB\-fintrin\-case\-upper\fR" 4
+.IX Item "-fintrin-case-upper"
+.IP "\fB\-fintrin\-case\-lower\fR" 4
+.IX Item "-fintrin-case-lower"
+.IP "\fB\-fintrin\-case\-any\fR" 4
+.IX Item "-fintrin-case-any"
+.PD
+Specify expected case for intrinsic names.
+\&\fB\-fintrin\-case\-lower\fR is the default.
+.IP "\fB\-fmatch\-case\-initcap\fR" 4
+.IX Item "-fmatch-case-initcap"
+.PD 0
+.IP "\fB\-fmatch\-case\-upper\fR" 4
+.IX Item "-fmatch-case-upper"
+.IP "\fB\-fmatch\-case\-lower\fR" 4
+.IX Item "-fmatch-case-lower"
+.IP "\fB\-fmatch\-case\-any\fR" 4
+.IX Item "-fmatch-case-any"
+.PD
+Specify expected case for keywords.
+\&\fB\-fmatch\-case\-lower\fR is the default.
+.IP "\fB\-fsource\-case\-upper\fR" 4
+.IX Item "-fsource-case-upper"
+.PD 0
+.IP "\fB\-fsource\-case\-lower\fR" 4
+.IX Item "-fsource-case-lower"
+.IP "\fB\-fsource\-case\-preserve\fR" 4
+.IX Item "-fsource-case-preserve"
+.PD
+Specify whether source text other than character and Hollerith constants
+is to be translated to uppercase, to lowercase, or preserved as is.
+\&\fB\-fsource\-case\-lower\fR is the default.
+.IP "\fB\-fsymbol\-case\-initcap\fR" 4
+.IX Item "-fsymbol-case-initcap"
+.PD 0
+.IP "\fB\-fsymbol\-case\-upper\fR" 4
+.IX Item "-fsymbol-case-upper"
+.IP "\fB\-fsymbol\-case\-lower\fR" 4
+.IX Item "-fsymbol-case-lower"
+.IP "\fB\-fsymbol\-case\-any\fR" 4
+.IX Item "-fsymbol-case-any"
+.PD
+Specify valid cases for user-defined symbol names.
+\&\fB\-fsymbol\-case\-any\fR is the default.
+.IP "\fB\-fcase\-strict\-upper\fR" 4
+.IX Item "-fcase-strict-upper"
+Same as \fB\-fintrin\-case\-upper \-fmatch\-case\-upper \-fsource\-case\-preserve
+\&\-fsymbol\-case\-upper\fR.
+(Requires all pertinent source to be in uppercase.)
+.IP "\fB\-fcase\-strict\-lower\fR" 4
+.IX Item "-fcase-strict-lower"
+Same as \fB\-fintrin\-case\-lower \-fmatch\-case\-lower \-fsource\-case\-preserve
+\&\-fsymbol\-case\-lower\fR.
+(Requires all pertinent source to be in lowercase.)
+.IP "\fB\-fcase\-initcap\fR" 4
+.IX Item "-fcase-initcap"
+Same as \fB\-fintrin\-case\-initcap \-fmatch\-case\-initcap \-fsource\-case\-preserve
+\&\-fsymbol\-case\-initcap\fR.
+(Requires all pertinent source to be in initial capitals,
+as in \fBPrint *,SqRt(Value)\fR.)
+.IP "\fB\-fcase\-upper\fR" 4
+.IX Item "-fcase-upper"
+Same as \fB\-fintrin\-case\-any \-fmatch\-case\-any \-fsource\-case\-upper
+\&\-fsymbol\-case\-any\fR.
+(Maps all pertinent source to uppercase.)
+.IP "\fB\-fcase\-lower\fR" 4
+.IX Item "-fcase-lower"
+Same as \fB\-fintrin\-case\-any \-fmatch\-case\-any \-fsource\-case\-lower
+\&\-fsymbol\-case\-any\fR.
+(Maps all pertinent source to lowercase.)
+.IP "\fB\-fcase\-preserve\fR" 4
+.IX Item "-fcase-preserve"
+Same as \fB\-fintrin\-case\-any \-fmatch\-case\-any \-fsource\-case\-preserve
+\&\-fsymbol\-case\-any\fR.
+(Preserves all case in user-defined symbols,
+while allowing any-case matching of intrinsics and keywords.
+For example, \fBcall Foo(i,I)\fR would pass two \fIdifferent\fR
+variables named \fBi\fR and \fBI\fR to a procedure named \fBFoo\fR.)
+.IP "\fB\-fbadu77\-intrinsics\-delete\fR" 4
+.IX Item "-fbadu77-intrinsics-delete"
+.PD 0
+.IP "\fB\-fbadu77\-intrinsics\-hide\fR" 4
+.IX Item "-fbadu77-intrinsics-hide"
+.IP "\fB\-fbadu77\-intrinsics\-disable\fR" 4
+.IX Item "-fbadu77-intrinsics-disable"
+.IP "\fB\-fbadu77\-intrinsics\-enable\fR" 4
+.IX Item "-fbadu77-intrinsics-enable"
+.PD
+Specify status of \s-1UNIX\s0 intrinsics having inappropriate forms.
+\&\fB\-fbadu77\-intrinsics\-enable\fR is the default.
+.IP "\fB\-ff2c\-intrinsics\-delete\fR" 4
+.IX Item "-ff2c-intrinsics-delete"
+.PD 0
+.IP "\fB\-ff2c\-intrinsics\-hide\fR" 4
+.IX Item "-ff2c-intrinsics-hide"
+.IP "\fB\-ff2c\-intrinsics\-disable\fR" 4
+.IX Item "-ff2c-intrinsics-disable"
+.IP "\fB\-ff2c\-intrinsics\-enable\fR" 4
+.IX Item "-ff2c-intrinsics-enable"
+.PD
+Specify status of f2c\-specific intrinsics.
+\&\fB\-ff2c\-intrinsics\-enable\fR is the default.
+.IP "\fB\-ff90\-intrinsics\-delete\fR" 4
+.IX Item "-ff90-intrinsics-delete"
+.PD 0
+.IP "\fB\-ff90\-intrinsics\-hide\fR" 4
+.IX Item "-ff90-intrinsics-hide"
+.IP "\fB\-ff90\-intrinsics\-disable\fR" 4
+.IX Item "-ff90-intrinsics-disable"
+.IP "\fB\-ff90\-intrinsics\-enable\fR" 4
+.IX Item "-ff90-intrinsics-enable"
+.PD
+Specify status of F90\-specific intrinsics.
+\&\fB\-ff90\-intrinsics\-enable\fR is the default.
+.IP "\fB\-fgnu\-intrinsics\-delete\fR" 4
+.IX Item "-fgnu-intrinsics-delete"
+.PD 0
+.IP "\fB\-fgnu\-intrinsics\-hide\fR" 4
+.IX Item "-fgnu-intrinsics-hide"
+.IP "\fB\-fgnu\-intrinsics\-disable\fR" 4
+.IX Item "-fgnu-intrinsics-disable"
+.IP "\fB\-fgnu\-intrinsics\-enable\fR" 4
+.IX Item "-fgnu-intrinsics-enable"
+.PD
+Specify status of Digital's COMPLEX-related intrinsics.
+\&\fB\-fgnu\-intrinsics\-enable\fR is the default.
+.IP "\fB\-fmil\-intrinsics\-delete\fR" 4
+.IX Item "-fmil-intrinsics-delete"
+.PD 0
+.IP "\fB\-fmil\-intrinsics\-hide\fR" 4
+.IX Item "-fmil-intrinsics-hide"
+.IP "\fB\-fmil\-intrinsics\-disable\fR" 4
+.IX Item "-fmil-intrinsics-disable"
+.IP "\fB\-fmil\-intrinsics\-enable\fR" 4
+.IX Item "-fmil-intrinsics-enable"
+.PD
+Specify status of MIL\-STD\-1753\-specific intrinsics.
+\&\fB\-fmil\-intrinsics\-enable\fR is the default.
+.IP "\fB\-funix\-intrinsics\-delete\fR" 4
+.IX Item "-funix-intrinsics-delete"
+.PD 0
+.IP "\fB\-funix\-intrinsics\-hide\fR" 4
+.IX Item "-funix-intrinsics-hide"
+.IP "\fB\-funix\-intrinsics\-disable\fR" 4
+.IX Item "-funix-intrinsics-disable"
+.IP "\fB\-funix\-intrinsics\-enable\fR" 4
+.IX Item "-funix-intrinsics-enable"
+.PD
+Specify status of \s-1UNIX\s0 intrinsics.
+\&\fB\-funix\-intrinsics\-enable\fR is the default.
+.IP "\fB\-fvxt\-intrinsics\-delete\fR" 4
+.IX Item "-fvxt-intrinsics-delete"
+.PD 0
+.IP "\fB\-fvxt\-intrinsics\-hide\fR" 4
+.IX Item "-fvxt-intrinsics-hide"
+.IP "\fB\-fvxt\-intrinsics\-disable\fR" 4
+.IX Item "-fvxt-intrinsics-disable"
+.IP "\fB\-fvxt\-intrinsics\-enable\fR" 4
+.IX Item "-fvxt-intrinsics-enable"
+.PD
+Specify status of \s-1VXT\s0 intrinsics.
+\&\fB\-fvxt\-intrinsics\-enable\fR is the default.
+.IP "\fB\-ffixed\-line\-length\-\fR\fIn\fR" 4
+.IX Item "-ffixed-line-length-n"
+Set column after which characters are ignored in typical fixed-form
+lines in the source file, and through which spaces are assumed (as
+if padded to that length) after the ends of short fixed-form lines.
+.Sp
+Popular values for \fIn\fR include 72 (the
+standard and the default), 80 (card image), and 132 (corresponds
+to ``extended\-source'' options in some popular compilers).
+\&\fIn\fR may be \fBnone\fR, meaning that the entire line is meaningful
+and that continued character constants never have implicit spaces appended
+to them to fill out the line.
+\&\fB\-ffixed\-line\-length\-0\fR means the same thing as
+\&\fB\-ffixed\-line\-length\-none\fR.
+.Sh "Options to Request or Suppress Warnings"
+.IX Subsection "Options to Request or Suppress Warnings"
+Warnings are diagnostic messages that report constructions which
+are not inherently erroneous but which are risky or suggest there
+might have been an error.
+.PP
+You can request many specific warnings with options beginning \fB\-W\fR,
+for example \fB\-Wimplicit\fR to request warnings on implicit
+declarations. Each of these specific warning options also has a
+negative form beginning \fB\-Wno\-\fR to turn off warnings;
+for example, \fB\-Wno\-implicit\fR. This manual lists only one of the
+two forms, whichever is not the default.
+.PP
+These options control the amount and kinds of warnings produced by \s-1GNU\s0
+Fortran:
+.IP "\fB\-fsyntax\-only\fR" 4
+.IX Item "-fsyntax-only"
+Check the code for syntax errors, but don't do anything beyond that.
+.IP "\fB\-pedantic\fR" 4
+.IX Item "-pedantic"
+Issue warnings for uses of extensions to \s-1ANSI\s0 \s-1FORTRAN\s0 77.
+\&\fB\-pedantic\fR also applies to C\-language constructs where they
+occur in \s-1GNU\s0 Fortran source files, such as use of \fB\ee\fR in a
+character constant within a directive like \fB#include\fR.
+.Sp
+Valid \s-1ANSI\s0 \s-1FORTRAN\s0 77 programs should compile properly with or without
+this option.
+However, without this option, certain \s-1GNU\s0 extensions and traditional
+Fortran features are supported as well.
+With this option, many of them are rejected.
+.Sp
+Some users try to use \fB\-pedantic\fR to check programs for strict \s-1ANSI\s0
+conformance.
+They soon find that it does not do quite what they want\-\-\-it finds some
+non-ANSI practices, but not all.
+However, improvements to \fBg77\fR in this area are welcome.
+.IP "\fB\-pedantic\-errors\fR" 4
+.IX Item "-pedantic-errors"
+Like \fB\-pedantic\fR, except that errors are produced rather than
+warnings.
+.IP "\fB\-fpedantic\fR" 4
+.IX Item "-fpedantic"
+Like \fB\-pedantic\fR, but applies only to Fortran constructs.
+.IP "\fB\-w\fR" 4
+.IX Item "-w"
+Inhibit all warning messages.
+.IP "\fB\-Wno\-globals\fR" 4
+.IX Item "-Wno-globals"
+Inhibit warnings about use of a name as both a global name
+(a subroutine, function, or block data program unit, or a
+common block) and implicitly as the name of an intrinsic
+in a source file.
+.Sp
+Also inhibit warnings about inconsistent invocations and/or
+definitions of global procedures (function and subroutines).
+Such inconsistencies include different numbers of arguments
+and different types of arguments.
+.IP "\fB\-Wimplicit\fR" 4
+.IX Item "-Wimplicit"
+Warn whenever a variable, array, or function is implicitly
+declared.
+Has an effect similar to using the \f(CW\*(C`IMPLICIT NONE\*(C'\fR statement
+in every program unit.
+(Some Fortran compilers provide this feature by an option
+named \fB\-u\fR or \fB/WARNINGS=DECLARATIONS\fR.)
+.IP "\fB\-Wunused\fR" 4
+.IX Item "-Wunused"
+Warn whenever a variable is unused aside from its declaration.
+.IP "\fB\-Wuninitialized\fR" 4
+.IX Item "-Wuninitialized"
+Warn whenever an automatic variable is used without first being initialized.
+.Sp
+These warnings are possible only in optimizing compilation,
+because they require data-flow information that is computed only
+when optimizing. If you don't specify \fB\-O\fR, you simply won't
+get these warnings.
+.Sp
+These warnings occur only for variables that are candidates for
+register allocation. Therefore, they do not occur for a variable
+whose address is taken, or whose size
+is other than 1, 2, 4 or 8 bytes. Also, they do not occur for
+arrays, even when they are in registers.
+.Sp
+Note that there might be no warning about a variable that is used only
+to compute a value that itself is never used, because such
+computations may be deleted by data-flow analysis before the warnings
+are printed.
+.Sp
+These warnings are made optional because \s-1GNU\s0 Fortran is not smart
+enough to see all the reasons why the code might be correct
+despite appearing to have an error. Here is one example of how
+this can happen:
+.Sp
+.Vb 6
+\& SUBROUTINE DISPAT(J)
+\& IF (J.EQ.1) I=1
+\& IF (J.EQ.2) I=4
+\& IF (J.EQ.3) I=5
+\& CALL FOO(I)
+\& END
+.Ve
+.Sp
+If the value of \f(CW\*(C`J\*(C'\fR is always 1, 2 or 3, then \f(CW\*(C`I\*(C'\fR is
+always initialized, but \s-1GNU\s0 Fortran doesn't know this. Here is
+another common case:
+.Sp
+.Vb 6
+\& SUBROUTINE MAYBE(FLAG)
+\& LOGICAL FLAG
+\& IF (FLAG) VALUE = 9.4
+\& ...
+\& IF (FLAG) PRINT *, VALUE
+\& END
+.Ve
+.Sp
+This has no bug because \f(CW\*(C`VALUE\*(C'\fR is used only if it is set.
+.IP "\fB\-Wall\fR" 4
+.IX Item "-Wall"
+The \fB\-Wunused\fR and \fB\-Wuninitialized\fR options combined.
+These are all the
+options which pertain to usage that we recommend avoiding and that we
+believe is easy to avoid.
+(As more warnings are added to \fBg77\fR some might
+be added to the list enabled by \fB\-Wall\fR.)
+.PP
+The remaining \fB\-W...\fR options are not implied by \fB\-Wall\fR
+because they warn about constructions that we consider reasonable to
+use, on occasion, in clean programs.
+.IP "\fB\-Wsurprising\fR" 4
+.IX Item "-Wsurprising"
+Warn about ``suspicious'' constructs that are interpreted
+by the compiler in a way that might well be surprising to
+someone reading the code.
+These differences can result in subtle, compiler-dependent
+(even machine\-dependent) behavioral differences.
+The constructs warned about include:
+.RS 4
+.IP "\(bu" 4
+Expressions having two arithmetic operators in a row, such
+as \fBX*\-Y\fR.
+Such a construct is nonstandard, and can produce
+unexpected results in more complicated situations such
+as \fBX**\-Y*Z\fR.
+\&\fBg77\fR along with many other compilers, interprets
+this example differently than many programmers, and a few
+other compilers.
+Specifically, \fBg77\fR interprets \fBX**\-Y*Z\fR as
+\&\fB(X**(\-Y))*Z\fR, while others might think it should
+be interpreted as \fBX**(\-(Y*Z))\fR.
+.Sp
+A revealing example is the constant expression \fB2**\-2*1.\fR,
+which \fBg77\fR evaluates to .25, while others might evaluate
+it to 0., the difference resulting from the way precedence affects
+type promotion.
+.Sp
+(The \fB\-fpedantic\fR option also warns about expressions
+having two arithmetic operators in a row.)
+.IP "\(bu" 4
+Expressions with a unary minus followed by an operand and then
+a binary operator other than plus or minus.
+For example, \fB\-2**2\fR produces a warning, because
+the precedence is \fB\-(2**2)\fR, yielding \-4, not
+\&\fB(\-2)**2\fR, which yields 4, and which might represent
+what a programmer expects.
+.Sp
+An example of an expression producing different results
+in a surprising way is \fB\-I*S\fR, where \fII\fR holds
+the value \fB\-2147483648\fR and \fIS\fR holds \fB0.5\fR.
+On many systems, negating \fII\fR results in the same
+value, not a positive number, because it is already the
+lower bound of what an \f(CW\*(C`INTEGER(KIND=1)\*(C'\fR variable can hold.
+So, the expression evaluates to a positive number, while
+the ``expected'' interpretation, \fB(\-I)*S\fR, would
+evaluate to a negative number.
+.Sp
+Even cases such as \fB\-I*J\fR produce warnings,
+even though, in most configurations and situations,
+there is no computational difference between the
+results of the two interpretations\-\-\-the purpose
+of this warning is to warn about differing interpretations
+and encourage a better style of coding, not to identify
+only those places where bugs might exist in the user's
+code.
+.IP "\(bu" 4
+\&\f(CW\*(C`DO\*(C'\fR loops with \f(CW\*(C`DO\*(C'\fR variables that are not
+of integral type\-\-\-that is, using \f(CW\*(C`REAL\*(C'\fR
+variables as loop control variables.
+Although such loops can be written to work in the
+``obvious'' way, the way \fBg77\fR is required by the
+Fortran standard to interpret such code is likely to
+be quite different from the way many programmers expect.
+(This is true of all \f(CW\*(C`DO\*(C'\fR loops, but the differences
+are pronounced for non-integral loop control variables.)
+.RE
+.RS 4
+.RE
+.IP "\fB\-Werror\fR" 4
+.IX Item "-Werror"
+Make all warnings into errors.
+.IP "\fB\-W\fR" 4
+.IX Item "-W"
+Turns on ``extra warnings'' and, if optimization is specified
+via \fB\-O\fR, the \fB\-Wuninitialized\fR option.
+(This might change in future versions of \fBg77\fR
+.Sp
+``Extra warnings'' are issued for:
+.RS 4
+.IP "\(bu" 4
+Unused parameters to a procedure (when \fB\-Wunused\fR also is
+specified).
+.IP "\(bu" 4
+Overflows involving floating-point constants (not available
+for certain configurations).
+.RE
+.RS 4
+.RE
+.PP
+Some of these have no effect when compiling programs written in Fortran:
+.IP "\fB\-Wcomment\fR" 4
+.IX Item "-Wcomment"
+.PD 0
+.IP "\fB\-Wformat\fR" 4
+.IX Item "-Wformat"
+.IP "\fB\-Wparentheses\fR" 4
+.IX Item "-Wparentheses"
+.IP "\fB\-Wswitch\fR" 4
+.IX Item "-Wswitch"
+.IP "\fB\-Wswitch\-default\fR" 4
+.IX Item "-Wswitch-default"
+.IP "\fB\-Wswitch\-enum\fR" 4
+.IX Item "-Wswitch-enum"
+.IP "\fB\-Wtraditional\fR" 4
+.IX Item "-Wtraditional"
+.IP "\fB\-Wshadow\fR" 4
+.IX Item "-Wshadow"
+.IP "\fB\-Wid\-clash\-\fR\fIlen\fR" 4
+.IX Item "-Wid-clash-len"
+.IP "\fB\-Wlarger\-than\-\fR\fIlen\fR" 4
+.IX Item "-Wlarger-than-len"
+.IP "\fB\-Wconversion\fR" 4
+.IX Item "-Wconversion"
+.IP "\fB\-Waggregate\-return\fR" 4
+.IX Item "-Waggregate-return"
+.IP "\fB\-Wredundant\-decls\fR" 4
+.IX Item "-Wredundant-decls"
+.PD
+These options all could have some relevant meaning for
+\&\s-1GNU\s0 Fortran programs, but are not yet supported.
+.Sh "Options for Debugging Your Program or \s-1GNU\s0 Fortran"
+.IX Subsection "Options for Debugging Your Program or GNU Fortran"
+\&\s-1GNU\s0 Fortran has various special options that are used for debugging
+either your program or \fBg77\fR
+.IP "\fB\-g\fR" 4
+.IX Item "-g"
+Produce debugging information in the operating system's native format
+(stabs, \s-1COFF\s0, \s-1XCOFF\s0, or \s-1DWARF\s0). \s-1GDB\s0 can work with this debugging
+information.
+.Sp
+A sample debugging session looks like this (note the use of the breakpoint):
+.Sp
+.Vb 24
+\& $ cat gdb.f
+\& PROGRAM PROG
+\& DIMENSION A(10)
+\& DATA A /1.,2.,3.,4.,5.,6.,7.,8.,9.,10./
+\& A(5) = 4.
+\& PRINT*,A
+\& END
+\& $ g77 -g -O gdb.f
+\& $ gdb a.out
+\& ...
+\& (gdb) break MAIN__
+\& Breakpoint 1 at 0x8048e96: file gdb.f, line 4.
+\& (gdb) run
+\& Starting program: /home/toon/g77-bugs/./a.out
+\& Breakpoint 1, MAIN__ () at gdb.f:4
+\& 4 A(5) = 4.
+\& Current language: auto; currently fortran
+\& (gdb) print a(5)
+\& $1 = 5
+\& (gdb) step
+\& 5 PRINT*,A
+\& (gdb) print a(5)
+\& $2 = 4
+\& ...
+.Ve
+.Sp
+One could also add the setting of the breakpoint and the first run command
+to the file \fI.gdbinit\fR in the current directory, to simplify the debugging
+session.
+.Sh "Options That Control Optimization"
+.IX Subsection "Options That Control Optimization"
+Most Fortran users will want to use no optimization when
+developing and testing programs, and use \fB\-O\fR or \fB\-O2\fR when
+compiling programs for late-cycle testing and for production use.
+However, note that certain diagnostics\-\-\-such as for uninitialized
+variables\-\-\-depend on the flow analysis done by \fB\-O\fR, i.e. you
+must use \fB\-O\fR or \fB\-O2\fR to get such diagnostics.
+.PP
+The following flags have particular applicability when
+compiling Fortran programs:
+.IP "\fB\-malign\-double\fR" 4
+.IX Item "-malign-double"
+(Intel x86 architecture only.)
+.Sp
+Noticeably improves performance of \fBg77\fR programs making
+heavy use of \f(CW\*(C`REAL(KIND=2)\*(C'\fR (\f(CW\*(C`DOUBLE PRECISION\*(C'\fR) data
+on some systems.
+In particular, systems using Pentium, Pentium Pro, 586, and
+686 implementations
+of the i386 architecture execute programs faster when
+\&\f(CW\*(C`REAL(KIND=2)\*(C'\fR (\f(CW\*(C`DOUBLE PRECISION\*(C'\fR) data are
+aligned on 64\-bit boundaries
+in memory.
+.Sp
+This option can, at least, make benchmark results more consistent
+across various system configurations, versions of the program,
+and data sets.
+.Sp
+\&\fINote:\fR The warning in the \fBgcc\fR documentation about
+this option does not apply, generally speaking, to Fortran
+code compiled by \fBg77\fR
+.Sp
+\&\fIAlso also note:\fR The negative form of \fB\-malign\-double\fR
+is \fB\-mno\-align\-double\fR, not \fB\-benign\-double\fR.
+.IP "\fB\-ffloat\-store\fR" 4
+.IX Item "-ffloat-store"
+Might help a Fortran program that depends on exact \s-1IEEE\s0 conformance on
+some machines, but might slow down a program that doesn't.
+.Sp
+This option is effective when the floating-point unit is set to work in
+\&\s-1IEEE\s0 854 `extended precision'\-\-\-as it typically is on x86 and m68k \s-1GNU\s0
+systems\-\-\-rather than \s-1IEEE\s0 754 double precision. \fB\-ffloat\-store\fR
+tries to remove the extra precision by spilling data from floating-point
+registers into memory and this typically involves a big performance
+hit. However, it doesn't affect intermediate results, so that it is
+only partially effective. `Excess precision' is avoided in code like:
+.Sp
+.Vb 2
+\& a = b + c
+\& d = a * e
+.Ve
+.Sp
+but not in code like:
+.Sp
+.Vb 1
+\& d = (b + c) * e
+.Ve
+.Sp
+For another, potentially better, way of controlling the precision,
+see \fBFloating-point precision\fR.
+.IP "\fB\-fforce\-mem\fR" 4
+.IX Item "-fforce-mem"
+.PD 0
+.IP "\fB\-fforce\-addr\fR" 4
+.IX Item "-fforce-addr"
+.PD
+Might improve optimization of loops.
+.IP "\fB\-fno\-inline\fR" 4
+.IX Item "-fno-inline"
+Don't compile statement functions inline.
+Might reduce the size of a program unit\-\-\-which might be at
+expense of some speed (though it should compile faster).
+Note that if you are not optimizing, no functions can be expanded inline.
+.IP "\fB\-ffast\-math\fR" 4
+.IX Item "-ffast-math"
+Might allow some programs designed to not be too dependent
+on \s-1IEEE\s0 behavior for floating-point to run faster, or die trying.
+Sets \fB\-funsafe\-math\-optimizations\fR, \fB\-ffinite\-math\-only\fR,
+and \fB\-fno\-trapping\-math\fR.
+.IP "\fB\-funsafe\-math\-optimizations\fR" 4
+.IX Item "-funsafe-math-optimizations"
+Allow optimizations that may be give incorrect results
+for certain \s-1IEEE\s0 inputs.
+.IP "\fB\-ffinite\-math\-only\fR" 4
+.IX Item "-ffinite-math-only"
+Allow optimizations for floating-point arithmetic that assume
+that arguments and results are not NaNs or +\-Infs.
+.Sp
+This option should never be turned on by any \fB\-O\fR option since
+it can result in incorrect output for programs which depend on
+an exact implementation of \s-1IEEE\s0 or \s-1ISO\s0 rules/specifications.
+.Sp
+The default is \fB\-fno\-finite\-math\-only\fR.
+.IP "\fB\-fno\-trapping\-math\fR" 4
+.IX Item "-fno-trapping-math"
+Allow the compiler to assume that floating-point arithmetic
+will not generate traps on any inputs. This is useful, for
+example, when running a program using \s-1IEEE\s0 \*(L"non\-stop\*(R"
+floating-point arithmetic.
+.IP "\fB\-fstrength\-reduce\fR" 4
+.IX Item "-fstrength-reduce"
+Might make some loops run faster.
+.IP "\fB\-frerun\-cse\-after\-loop\fR" 4
+.IX Item "-frerun-cse-after-loop"
+.PD 0
+.IP "\fB\-fexpensive\-optimizations\fR" 4
+.IX Item "-fexpensive-optimizations"
+.IP "\fB\-fdelayed\-branch\fR" 4
+.IX Item "-fdelayed-branch"
+.IP "\fB\-fschedule\-insns\fR" 4
+.IX Item "-fschedule-insns"
+.IP "\fB\-fschedule\-insns2\fR" 4
+.IX Item "-fschedule-insns2"
+.IP "\fB\-fcaller\-saves\fR" 4
+.IX Item "-fcaller-saves"
+.PD
+Might improve performance on some code.
+.IP "\fB\-funroll\-loops\fR" 4
+.IX Item "-funroll-loops"
+Typically improves performance on code using iterative \f(CW\*(C`DO\*(C'\fR loops by
+unrolling them and is probably generally appropriate for Fortran, though
+it is not turned on at any optimization level.
+Note that outer loop unrolling isn't done specifically; decisions about
+whether to unroll a loop are made on the basis of its instruction count.
+.Sp
+Also, no `loop discovery'[1] is done, so only loops written with \f(CW\*(C`DO\*(C'\fR
+benefit from loop optimizations, including\-\-\-but not limited
+to\-\-\-unrolling. Loops written with \f(CW\*(C`IF\*(C'\fR and \f(CW\*(C`GOTO\*(C'\fR are not
+currently recognized as such. This option unrolls only iterative
+\&\f(CW\*(C`DO\*(C'\fR loops, not \f(CW\*(C`DO WHILE\*(C'\fR loops.
+.IP "\fB\-funroll\-all\-loops\fR" 4
+.IX Item "-funroll-all-loops"
+Probably improves performance on code using \f(CW\*(C`DO WHILE\*(C'\fR loops by
+unrolling them in addition to iterative \f(CW\*(C`DO\*(C'\fR loops. In the absence
+of \f(CW\*(C`DO WHILE\*(C'\fR, this option is equivalent to \fB\-funroll\-loops\fR
+but possibly slower.
+.IP "\fB\-fno\-move\-all\-movables\fR" 4
+.IX Item "-fno-move-all-movables"
+.PD 0
+.IP "\fB\-fno\-reduce\-all\-givs\fR" 4
+.IX Item "-fno-reduce-all-givs"
+.IP "\fB\-fno\-rerun\-loop\-opt\fR" 4
+.IX Item "-fno-rerun-loop-opt"
+.PD
+In general, the optimizations enabled with these options will lead to
+faster code being generated by \s-1GNU\s0 Fortran; hence they are enabled by default
+when issuing the \fBg77\fR command.
+.Sp
+\&\fB\-fmove\-all\-movables\fR and \fB\-freduce\-all\-givs\fR will enable
+loop optimization to move all loop-invariant index computations in nested
+loops over multi-rank array dummy arguments out of these loops.
+.Sp
+\&\fB\-frerun\-loop\-opt\fR will move offset calculations resulting
+from the fact that Fortran arrays by default have a lower bound of 1
+out of the loops.
+.Sp
+These three options are intended to be removed someday, once
+loop optimization is sufficiently advanced to perform all those
+transformations without help from these options.
+.Sh "Options Controlling the Preprocessor"
+.IX Subsection "Options Controlling the Preprocessor"
+These options control the C preprocessor, which is run on each C source
+file before actual compilation.
+.PP
+Some of these options also affect how \fBg77\fR processes the
+\&\f(CW\*(C`INCLUDE\*(C'\fR directive.
+Since this directive is processed even when preprocessing
+is not requested, it is not described in this section.
+.PP
+However, the \f(CW\*(C`INCLUDE\*(C'\fR directive does not apply
+preprocessing to the contents of the included file itself.
+.PP
+Therefore, any file that contains preprocessor directives
+(such as \f(CW\*(C`#include\*(C'\fR, \f(CW\*(C`#define\*(C'\fR, and \f(CW\*(C`#if\*(C'\fR)
+must be included via the \f(CW\*(C`#include\*(C'\fR directive, not
+via the \f(CW\*(C`INCLUDE\*(C'\fR directive.
+Therefore, any file containing preprocessor directives,
+if included, is necessarily included by a file that itself
+contains preprocessor directives.
+.Sh "Options for Directory Search"
+.IX Subsection "Options for Directory Search"
+These options affect how the \fBcpp\fR preprocessor searches
+for files specified via the \f(CW\*(C`#include\*(C'\fR directive.
+Therefore, when compiling Fortran programs, they are meaningful
+when the preprocessor is used.
+.PP
+Some of these options also affect how \fBg77\fR searches
+for files specified via the \f(CW\*(C`INCLUDE\*(C'\fR directive,
+although files included by that directive are not,
+themselves, preprocessed.
+These options are:
+.IP "\fB\-I\-\fR" 4
+.IX Item "-I-"
+.PD 0
+.IP "\fB\-I\fR\fIdir\fR" 4
+.IX Item "-Idir"
+.PD
+These affect interpretation of the \f(CW\*(C`INCLUDE\*(C'\fR directive
+(as well as of the \f(CW\*(C`#include\*(C'\fR directive of the \fBcpp\fR
+preprocessor).
+.Sp
+Note that \fB\-I\fR\fIdir\fR must be specified \fIwithout\fR any
+spaces between \fB\-I\fR and the directory name\-\-\-that is,
+\&\fB\-Ifoo/bar\fR is valid, but \fB\-I foo/bar\fR
+is rejected by the \fBg77\fR compiler (though the preprocessor supports
+the latter form).
+Also note that the general behavior of \fB\-I\fR and
+\&\f(CW\*(C`INCLUDE\*(C'\fR is pretty much the same as of \fB\-I\fR with
+\&\f(CW\*(C`#include\*(C'\fR in the \fBcpp\fR preprocessor, with regard to
+looking for \fIheader.gcc\fR files and other such things.
+.Sh "Options for Code Generation Conventions"
+.IX Subsection "Options for Code Generation Conventions"
+These machine-independent options control the interface conventions
+used in code generation.
+.PP
+Most of them have both positive and negative forms; the negative form
+of \fB\-ffoo\fR would be \fB\-fno\-foo\fR. In the table below, only
+one of the forms is listed\-\-\-the one which is not the default. You
+can figure out the other form by either removing \fBno\-\fR or adding
+it.
+.IP "\fB\-fno\-automatic\fR" 4
+.IX Item "-fno-automatic"
+Treat each program unit as if the \f(CW\*(C`SAVE\*(C'\fR statement was specified
+for every local variable and array referenced in it.
+Does not affect common blocks.
+(Some Fortran compilers provide this option under
+the name \fB\-static\fR.)
+.IP "\fB\-finit\-local\-zero\fR" 4
+.IX Item "-finit-local-zero"
+Specify that variables and arrays that are local to a program unit
+(not in a common block and not passed as an argument) are to be initialized
+to binary zeros.
+.Sp
+Since there is a run-time penalty for initialization of variables
+that are not given the \f(CW\*(C`SAVE\*(C'\fR attribute, it might be a
+good idea to also use \fB\-fno\-automatic\fR with \fB\-finit\-local\-zero\fR.
+.IP "\fB\-fno\-f2c\fR" 4
+.IX Item "-fno-f2c"
+Do not generate code designed to be compatible with code generated
+by \fBf2c\fR use the \s-1GNU\s0 calling conventions instead.
+.Sp
+The \fBf2c\fR calling conventions require functions that return
+type \f(CW\*(C`REAL(KIND=1)\*(C'\fR to actually return the C type \f(CW\*(C`double\*(C'\fR,
+and functions that return type \f(CW\*(C`COMPLEX\*(C'\fR to return the
+values via an extra argument in the calling sequence that points
+to where to store the return value.
+Under the \s-1GNU\s0 calling conventions, such functions simply return
+their results as they would in \s-1GNU\s0 C\-\-\-\f(CW\*(C`REAL(KIND=1)\*(C'\fR functions
+return the C type \f(CW\*(C`float\*(C'\fR, and \f(CW\*(C`COMPLEX\*(C'\fR functions
+return the \s-1GNU\s0 C type \f(CW\*(C`complex\*(C'\fR (or its \f(CW\*(C`struct\*(C'\fR
+equivalent).
+.Sp
+This does not affect the generation of code that interfaces with the
+\&\f(CW\*(C`libg2c\*(C'\fR library.
+.Sp
+However, because the \f(CW\*(C`libg2c\*(C'\fR library uses \fBf2c\fR
+calling conventions, \fBg77\fR rejects attempts to pass
+intrinsics implemented by routines in this library as actual
+arguments when \fB\-fno\-f2c\fR is used, to avoid bugs when
+they are actually called by code expecting the \s-1GNU\s0 calling
+conventions to work.
+.Sp
+For example, \fB\s-1INTRINSIC\s0 \s-1ABS\s0;CALL \s-1FOO\s0(\s-1ABS\s0)\fR is
+rejected when \fB\-fno\-f2c\fR is in force.
+(Future versions of the \fBg77\fR run-time library might
+offer routines that provide GNU-callable versions of the
+routines that implement the \fBf2c\fR intrinsics
+that may be passed as actual arguments, so that
+valid programs need not be rejected when \fB\-fno\-f2c\fR
+is used.)
+.Sp
+\&\fBCaution:\fR If \fB\-fno\-f2c\fR is used when compiling any
+source file used in a program, it must be used when compiling
+\&\fIall\fR Fortran source files used in that program.
+.IP "\fB\-ff2c\-library\fR" 4
+.IX Item "-ff2c-library"
+Specify that use of \f(CW\*(C`libg2c\*(C'\fR (or the original \f(CW\*(C`libf2c\*(C'\fR)
+is required.
+This is the default for the current version of \fBg77\fR
+.Sp
+Currently it is not
+valid to specify \fB\-fno\-f2c\-library\fR.
+This option is provided so users can specify it in shell
+scripts that build programs and libraries that require the
+\&\f(CW\*(C`libf2c\*(C'\fR library, even when being compiled by future
+versions of \fBg77\fR that might otherwise default to
+generating code for an incompatible library.
+.IP "\fB\-fno\-underscoring\fR" 4
+.IX Item "-fno-underscoring"
+Do not transform names of entities specified in the Fortran
+source file by appending underscores to them.
+.Sp
+With \fB\-funderscoring\fR in effect, \fBg77\fR appends two underscores
+to names with underscores and one underscore to external names with
+no underscores. (\fBg77\fR also appends two underscores to internal
+names with underscores to avoid naming collisions with external names.
+The \fB\-fno\-second\-underscore\fR option disables appending of the
+second underscore in all cases.)
+.Sp
+This is done to ensure compatibility with code produced by many
+\&\s-1UNIX\s0 Fortran compilers, including \fBf2c\fR which perform the
+same transformations.
+.Sp
+Use of \fB\-fno\-underscoring\fR is not recommended unless you are
+experimenting with issues such as integration of (\s-1GNU\s0) Fortran into
+existing system environments (vis\-a\-vis existing libraries, tools, and
+so on).
+.Sp
+For example, with \fB\-funderscoring\fR, and assuming other defaults like
+\&\fB\-fcase\-lower\fR and that \fBj()\fR and \fB\f(BImax_count()\fB\fR are
+external functions while \fBmy_var\fR and \fBlvar\fR are local variables,
+a statement like
+.Sp
+.Vb 1
+\& I = J() + MAX_COUNT (MY_VAR, LVAR)
+.Ve
+.Sp
+is implemented as something akin to:
+.Sp
+.Vb 1
+\& i = j_() + max_count__(&my_var__, &lvar);
+.Ve
+.Sp
+With \fB\-fno\-underscoring\fR, the same statement is implemented as:
+.Sp
+.Vb 1
+\& i = j() + max_count(&my_var, &lvar);
+.Ve
+.Sp
+Use of \fB\-fno\-underscoring\fR allows direct specification of
+user-defined names while debugging and when interfacing \fBg77\fR
+code with other languages.
+.Sp
+Note that just because the names match does \fInot\fR mean that the
+interface implemented by \fBg77\fR for an external name matches the
+interface implemented by some other language for that same name.
+That is, getting code produced by \fBg77\fR to link to code produced
+by some other compiler using this or any other method can be only a
+small part of the overall solution\-\-\-getting the code generated by
+both compilers to agree on issues other than naming can require
+significant effort, and, unlike naming disagreements, linkers normally
+cannot detect disagreements in these other areas.
+.Sp
+Also, note that with \fB\-fno\-underscoring\fR, the lack of appended
+underscores introduces the very real possibility that a user-defined
+external name will conflict with a name in a system library, which
+could make finding unresolved-reference bugs quite difficult in some
+cases\-\-\-they might occur at program run time, and show up only as
+buggy behavior at run time.
+.Sp
+In future versions of \fBg77\fR we hope to improve naming and linking
+issues so that debugging always involves using the names as they appear
+in the source, even if the names as seen by the linker are mangled to
+prevent accidental linking between procedures with incompatible
+interfaces.
+.IP "\fB\-fno\-second\-underscore\fR" 4
+.IX Item "-fno-second-underscore"
+Do not append a second underscore to names of entities specified
+in the Fortran source file.
+.Sp
+This option has no effect if \fB\-fno\-underscoring\fR is
+in effect.
+.Sp
+Otherwise, with this option, an external name such as \fB\s-1MAX_COUNT\s0\fR
+is implemented as a reference to the link-time external symbol
+\&\fBmax_count_\fR, instead of \fBmax_count_\|_\fR.
+.IP "\fB\-fno\-ident\fR" 4
+.IX Item "-fno-ident"
+Ignore the \fB#ident\fR directive.
+.IP "\fB\-fzeros\fR" 4
+.IX Item "-fzeros"
+Treat initial values of zero as if they were any other value.
+.Sp
+As of version 0.5.18, \fBg77\fR normally treats \f(CW\*(C`DATA\*(C'\fR and
+other statements that are used to specify initial values of zero
+for variables and arrays as if no values were actually specified,
+in the sense that no diagnostics regarding multiple initializations
+are produced.
+.Sp
+This is done to speed up compiling of programs that initialize
+large arrays to zeros.
+.Sp
+Use \fB\-fzeros\fR to revert to the simpler, slower behavior
+that can catch multiple initializations by keeping track of
+all initializations, zero or otherwise.
+.Sp
+\&\fICaution:\fR Future versions of \fBg77\fR might disregard this option
+(and its negative form, the default) or interpret it somewhat
+differently.
+The interpretation changes will affect only non-standard
+programs; standard-conforming programs should not be affected.
+.IP "\fB\-femulate\-complex\fR" 4
+.IX Item "-femulate-complex"
+Implement \f(CW\*(C`COMPLEX\*(C'\fR arithmetic via emulation,
+instead of using the facilities of
+the \fBgcc\fR back end that provide direct support of
+\&\f(CW\*(C`complex\*(C'\fR arithmetic.
+.Sp
+(\fBgcc\fR had some bugs in its back-end support
+for \f(CW\*(C`complex\*(C'\fR arithmetic, due primarily to the support not being
+completed as of version 2.8.1 and \f(CW\*(C`egcs\*(C'\fR 1.1.2.)
+.Sp
+Use \fB\-femulate\-complex\fR if you suspect code-generation bugs,
+or experience compiler crashes,
+that might result from \fBg77\fR using the \f(CW\*(C`COMPLEX\*(C'\fR support
+in the \fBgcc\fR back end.
+If using that option fixes the bugs or crashes you are seeing,
+that indicates a likely \fBg77\fR bugs
+(though, all compiler crashes are considered bugs),
+so, please report it.
+(Note that the known bugs, now believed fixed, produced compiler crashes
+rather than causing the generation of incorrect code.)
+.Sp
+Use of this option should not affect how Fortran code compiled
+by \fBg77\fR works in terms of its interfaces to other code,
+e.g. that compiled by \fBf2c\fR
+.Sp
+As of \s-1GCC\s0 version 3.0, this option is not necessary anymore.
+.Sp
+\&\fICaution:\fR Future versions of \fBg77\fR might ignore both forms
+of this option.
+.IP "\fB\-falias\-check\fR" 4
+.IX Item "-falias-check"
+.PD 0
+.IP "\fB\-fargument\-alias\fR" 4
+.IX Item "-fargument-alias"
+.IP "\fB\-fargument\-noalias\fR" 4
+.IX Item "-fargument-noalias"
+.IP "\fB\-fno\-argument\-noalias\-global\fR" 4
+.IX Item "-fno-argument-noalias-global"
+.PD
+\&\fIVersion info:\fR
+These options are not supported by
+versions of \fBg77\fR based on \fBgcc\fR version 2.8.
+.Sp
+These options specify to what degree aliasing
+(overlap)
+is permitted between
+arguments (passed as pointers) and \f(CW\*(C`COMMON\*(C'\fR (external, or
+public) storage.
+.Sp
+The default for Fortran code, as mandated by the \s-1FORTRAN\s0 77 and
+Fortran 90 standards, is \fB\-fargument\-noalias\-global\fR.
+The default for code written in the C language family is
+\&\fB\-fargument\-alias\fR.
+.Sp
+Note that, on some systems, compiling with \fB\-fforce\-addr\fR in
+effect can produce more optimal code when the default aliasing
+options are in effect (and when optimization is enabled).
+.IP "\fB\-fno\-globals\fR" 4
+.IX Item "-fno-globals"
+Disable diagnostics about inter-procedural
+analysis problems, such as disagreements about the
+type of a function or a procedure's argument,
+that might cause a compiler crash when attempting
+to inline a reference to a procedure within a
+program unit.
+(The diagnostics themselves are still produced, but
+as warnings, unless \fB\-Wno\-globals\fR is specified,
+in which case no relevant diagnostics are produced.)
+.Sp
+Further, this option disables such inlining, to
+avoid compiler crashes resulting from incorrect
+code that would otherwise be diagnosed.
+.Sp
+As such, this option might be quite useful when
+compiling existing, ``working'' code that happens
+to have a few bugs that do not generally show themselves,
+but which \fBg77\fR diagnoses.
+.Sp
+Use of this option therefore has the effect of
+instructing \fBg77\fR to behave more like it did
+up through version 0.5.19.1, when it paid little or
+no attention to disagreements between program units
+about a procedure's type and argument information,
+and when it performed no inlining of procedures
+(except statement functions).
+.Sp
+Without this option, \fBg77\fR defaults to performing
+the potentially inlining procedures as it started doing
+in version 0.5.20, but as of version 0.5.21, it also
+diagnoses disagreements that might cause such inlining
+to crash the compiler as (fatal) errors,
+and warns about similar disagreements
+that are currently believed to not
+likely to result in the compiler later crashing
+or producing incorrect code.
+.IP "\fB\-fflatten\-arrays\fR" 4
+.IX Item "-fflatten-arrays"
+Use back end's C\-like constructs
+(pointer plus offset)
+instead of its \f(CW\*(C`ARRAY_REF\*(C'\fR construct
+to handle all array references.
+.Sp
+\&\fINote:\fR This option is not supported.
+It is intended for use only by \fBg77\fR developers,
+to evaluate code-generation issues.
+It might be removed at any time.
+.IP "\fB\-fbounds\-check\fR" 4
+.IX Item "-fbounds-check"
+.PD 0
+.IP "\fB\-ffortran\-bounds\-check\fR" 4
+.IX Item "-ffortran-bounds-check"
+.PD
+Enable generation of run-time checks for array subscripts
+and substring start and end points
+against the (locally) declared minimum and maximum values.
+.Sp
+The current implementation uses the \f(CW\*(C`libf2c\*(C'\fR
+library routine \f(CW\*(C`s_rnge\*(C'\fR to print the diagnostic.
+.Sp
+However, whereas \fBf2c\fR generates a single check per
+reference for a multi-dimensional array, of the computed
+offset against the valid offset range (0 through the size of the array),
+\&\fBg77\fR generates a single check per \fIsubscript\fR expression.
+This catches some cases of potential bugs that \fBf2c\fR does not,
+such as references to below the beginning of an assumed-size array.
+.Sp
+\&\fBg77\fR also generates checks for \f(CW\*(C`CHARACTER\*(C'\fR substring references,
+something \fBf2c\fR currently does not do.
+.Sp
+Use the new \fB\-ffortran\-bounds\-check\fR option
+to specify bounds-checking for only the Fortran code you are compiling,
+not necessarily for code written in other languages.
+.Sp
+\&\fINote:\fR To provide more detailed information on the offending subscript,
+\&\fBg77\fR provides the \f(CW\*(C`libg2c\*(C'\fR run-time library routine \f(CW\*(C`s_rnge\*(C'\fR
+with somewhat differently-formatted information.
+Here's a sample diagnostic:
+.Sp
+.Vb 3
+\& Subscript out of range on file line 4, procedure rnge.f/bf.
+\& Attempt to access the -6-th element of variable b[subscript-2-of-2].
+\& Aborted
+.Ve
+.Sp
+The above message indicates that the offending source line is
+line 4 of the file \fIrnge.f\fR,
+within the program unit (or statement function) named \fBbf\fR.
+The offended array is named \fBb\fR.
+The offended array dimension is the second for a two-dimensional array,
+and the offending, computed subscript expression was \fB\-6\fR.
+.Sp
+For a \f(CW\*(C`CHARACTER\*(C'\fR substring reference, the second line has
+this appearance:
+.Sp
+.Vb 1
+\& Attempt to access the 11-th element of variable a[start-substring].
+.Ve
+.Sp
+This indicates that the offended \f(CW\*(C`CHARACTER\*(C'\fR variable or array
+is named \fBa\fR,
+the offended substring position is the starting (leftmost) position,
+and the offending substring expression is \fB11\fR.
+.Sp
+(Though the verbage of \f(CW\*(C`s_rnge\*(C'\fR is not ideal
+for the purpose of the \fBg77\fR compiler,
+the above information should provide adequate diagnostic abilities
+to it users.)
+.PP
+Some of these do \fInot\fR work when compiling programs written in Fortran:
+.IP "\fB\-fpcc\-struct\-return\fR" 4
+.IX Item "-fpcc-struct-return"
+.PD 0
+.IP "\fB\-freg\-struct\-return\fR" 4
+.IX Item "-freg-struct-return"
+.PD
+You should not use these except strictly the same way as you
+used them to build the version of \f(CW\*(C`libg2c\*(C'\fR with which
+you will be linking all code compiled by \fBg77\fR with the
+same option.
+.IP "\fB\-fshort\-double\fR" 4
+.IX Item "-fshort-double"
+This probably either has no effect on Fortran programs, or
+makes them act loopy.
+.IP "\fB\-fno\-common\fR" 4
+.IX Item "-fno-common"
+Do not use this when compiling Fortran programs,
+or there will be Trouble.
+.IP "\fB\-fpack\-struct\fR" 4
+.IX Item "-fpack-struct"
+This probably will break any calls to the \f(CW\*(C`libg2c\*(C'\fR library,
+at the very least, even if it is built with the same option.
+.SH "ENVIRONMENT"
+.IX Header "ENVIRONMENT"
+\&\s-1GNU\s0 Fortran currently does not make use of any environment
+variables to control its operation above and beyond those
+that affect the operation of \fBgcc\fR.
+.SH "BUGS"
+.IX Header "BUGS"
+For instructions on reporting bugs, see
+<\fBhttp://gcc.gnu.org/bugs.html\fR>. Use of the \fBgccbug\fR
+script to report bugs is recommended.
+.SH "FOOTNOTES"
+.IX Header "FOOTNOTES"
+.IP "1." 4
+\&\fIloop discovery\fR refers to the
+process by which a compiler, or indeed any reader of a program,
+determines which portions of the program are more likely to be executed
+repeatedly as it is being run. Such discovery typically is done early
+when compiling using optimization techniques, so the ``discovered''
+loops get more attention\-\-\-and more run-time resources, such as
+registers\-\-\-from the compiler. It is easy to ``discover'' loops that are
+constructed out of looping constructs in the language
+(such as Fortran's \f(CW\*(C`DO\*(C'\fR). For some programs, ``discovering'' loops
+constructed out of lower-level constructs (such as \f(CW\*(C`IF\*(C'\fR and
+\&\f(CW\*(C`GOTO\*(C'\fR) can lead to generation of more optimal code
+than otherwise.
+.SH "SEE ALSO"
+.IX Header "SEE ALSO"
+\&\fIgpl\fR\|(7), \fIgfdl\fR\|(7), \fIfsf\-funding\fR\|(7),
+\&\fIcpp\fR\|(1), \fIgcov\fR\|(1), \fIgcc\fR\|(1), \fIas\fR\|(1), \fIld\fR\|(1), \fIgdb\fR\|(1), \fIadb\fR\|(1), \fIdbx\fR\|(1), \fIsdb\fR\|(1)
+and the Info entries for \fIgcc\fR, \fIcpp\fR, \fIg77\fR, \fIas\fR,
+\&\fIld\fR, \fIbinutils\fR and \fIgdb\fR.
+.SH "AUTHOR"
+.IX Header "AUTHOR"
+See the Info entry for \fBg77\fR for contributors to \s-1GCC\s0 and G77.
+.SH "COPYRIGHT"
+.IX Header "COPYRIGHT"
+Copyright (c) 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2004
+Free Software Foundation, Inc.
+.PP
+Permission is granted to copy, distribute and/or modify this document
+under the terms of the \s-1GNU\s0 Free Documentation License, Version 1.2 or
+any later version published by the Free Software Foundation; with the
+Invariant Sections being ``\s-1GNU\s0 General Public License'' and ``Funding
+Free Software'', the Front-Cover texts being (a) (see below), and with
+the Back-Cover Texts being (b) (see below). A copy of the license is
+included in the \fIgfdl\fR\|(7) man page.
+.PP
+(a) The \s-1FSF\s0's Front-Cover Text is:
+.PP
+.Vb 1
+\& A GNU Manual
+.Ve
+.PP
+(b) The \s-1FSF\s0's Back-Cover Text is:
+.PP
+.Vb 3
+\& You have freedom to copy and modify this GNU Manual, like GNU
+\& software. Copies published by the Free Software Foundation raise
+\& funds for GNU development.
+.Ve