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.TH "CLANG" "1" "Jul 10, 2016" "3.8" "Clang"

.SH NAME

clang \- the Clang C, C++, and Objective-C compiler

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.SH SYNOPSIS

.sp

\fBclang\fP [\fIoptions\fP] \fIfilename ...\fP

.SH DESCRIPTION

.sp

\fBclang\fP is a C, C++, and Objective\-C compiler which encompasses

preprocessing, parsing, optimization, code generation, assembly, and linking.

Depending on which high\-level mode setting is passed, Clang will stop before

doing a full link.  While Clang is highly integrated, it is important to

understand the stages of compilation, to understand how to invoke it.  These

stages are:

.INDENT 0.0

.TP

.B Driver

The clang executable is actually a small driver which controls the overall

execution of other tools such as the compiler, assembler and linker.

Typically you do not need to interact with the driver, but you

transparently use it to run the other tools.

.TP

.B Preprocessing

This stage handles tokenization of the input source file, macro expansion,

#include expansion and handling of other preprocessor directives.  The

output of this stage is typically called a ".i" (for C), ".ii" (for C++),

".mi" (for Objective\-C), or ".mii" (for Objective\-C++) file.

.TP

.B Parsing and Semantic Analysis

This stage parses the input file, translating preprocessor tokens into a

parse tree.  Once in the form of a parse tree, it applies semantic

analysis to compute types for expressions as well and determine whether

the code is well formed. This stage is responsible for generating most of

the compiler warnings as well as parse errors. The output of this stage is

an "Abstract Syntax Tree" (AST).

.TP

.B Code Generation and Optimization

This stage translates an AST into low\-level intermediate code (known as

"LLVM IR") and ultimately to machine code.  This phase is responsible for

optimizing the generated code and handling target\-specific code generation.

The output of this stage is typically called a ".s" file or "assembly" file.

.sp

Clang also supports the use of an integrated assembler, in which the code

generator produces object files directly. This avoids the overhead of

generating the ".s" file and of calling the target assembler.

.TP

.B Assembler

This stage runs the target assembler to translate the output of the

compiler into a target object file. The output of this stage is typically

called a ".o" file or "object" file.

.TP

.B Linker

This stage runs the target linker to merge multiple object files into an

executable or dynamic library. The output of this stage is typically called

an "a.out", ".dylib" or ".so" file.

.UNINDENT

.sp

\fBClang Static Analyzer\fP

.sp

The Clang Static Analyzer is a tool that scans source code to try to find bugs

through code analysis.  This tool uses many parts of Clang and is built into

the same driver.  Please see <\fI\%http://clang\-analyzer.llvm.org\fP> for more details

on how to use the static analyzer.

.SH OPTIONS

.SS Stage Selection Options

.INDENT 0.0

.TP

.B \-E

Run the preprocessor stage.

.UNINDENT

.INDENT 0.0

.TP

.B \-fsyntax\-only

Run the preprocessor, parser and type checking stages.

.UNINDENT

.INDENT 0.0

.TP

.B \-S

Run the previous stages as well as LLVM generation and optimization stages

and target\-specific code generation, producing an assembly file.

.UNINDENT

.INDENT 0.0

.TP

.B \-c

Run all of the above, plus the assembler, generating a target ".o" object file.

.UNINDENT

.INDENT 0.0

.TP

.B no stage selection option

If no stage selection option is specified, all stages above are run, and the

linker is run to combine the results into an executable or shared library.

.UNINDENT

.SS Language Selection and Mode Options

.INDENT 0.0

.TP

.B \-x <language>

Treat subsequent input files as having type language.

.UNINDENT

.INDENT 0.0

.TP

.B \-std=<language>

Specify the language standard to compile for.

.UNINDENT

.INDENT 0.0

.TP

.B \-stdlib=<library>

Specify the C++ standard library to use; supported options are libstdc++ and

libc++.

.UNINDENT

.INDENT 0.0

.TP

.B \-ansi

Same as \-std=c89.

.UNINDENT

.INDENT 0.0

.TP

.B \-ObjC, \-ObjC++

Treat source input files as Objective\-C and Object\-C++ inputs respectively.

.UNINDENT

.INDENT 0.0

.TP

.B \-trigraphs

Enable trigraphs.

.UNINDENT

.INDENT 0.0

.TP

.B \-ffreestanding

Indicate that the file should be compiled for a freestanding, not a hosted,

environment.

.UNINDENT

.INDENT 0.0

.TP

.B \-fno\-builtin

Disable special handling and optimizations of builtin functions like

\fBstrlen()\fP and \fBmalloc()\fP\&.

.UNINDENT

.INDENT 0.0

.TP

.B \-fmath\-errno

Indicate that math functions should be treated as updating \fBerrno\fP\&.

.UNINDENT

.INDENT 0.0

.TP

.B \-fpascal\-strings

Enable support for Pascal\-style strings with "\epfoo".

.UNINDENT

.INDENT 0.0

.TP

.B \-fms\-extensions

Enable support for Microsoft extensions.

.UNINDENT

.INDENT 0.0

.TP

.B \-fmsc\-version=

Set _MSC_VER. Defaults to 1300 on Windows. Not set otherwise.

.UNINDENT

.INDENT 0.0

.TP

.B \-fborland\-extensions

Enable support for Borland extensions.

.UNINDENT

.INDENT 0.0

.TP

.B \-fwritable\-strings

Make all string literals default to writable.  This disables uniquing of

strings and other optimizations.

.UNINDENT

.INDENT 0.0

.TP

.B \-flax\-vector\-conversions

Allow loose type checking rules for implicit vector conversions.

.UNINDENT

.INDENT 0.0

.TP

.B \-fblocks

Enable the "Blocks" language feature.

.UNINDENT

.INDENT 0.0

.TP

.B \-fobjc\-gc\-only

Indicate that Objective\-C code should be compiled in GC\-only mode, which only

works when Objective\-C Garbage Collection is enabled.

.UNINDENT

.INDENT 0.0

.TP

.B \-fobjc\-gc

Indicate that Objective\-C code should be compiled in hybrid\-GC mode, which

works with both GC and non\-GC mode.

.UNINDENT

.INDENT 0.0

.TP

.B \-fobjc\-abi\-version=version

Select the Objective\-C ABI version to use. Available versions are 1 (legacy

"fragile" ABI), 2 (non\-fragile ABI 1), and 3 (non\-fragile ABI 2).

.UNINDENT

.INDENT 0.0

.TP

.B \-fobjc\-nonfragile\-abi\-version=<version>

Select the Objective\-C non\-fragile ABI version to use by default. This will

only be used as the Objective\-C ABI when the non\-fragile ABI is enabled

(either via \fI\%\-fobjc\-nonfragile\-abi\fP, or because it is the platform

default).

.UNINDENT

.INDENT 0.0

.TP

.B \-fobjc\-nonfragile\-abi

Enable use of the Objective\-C non\-fragile ABI. On platforms for which this is

the default ABI, it can be disabled with \fB\-fno\-objc\-nonfragile\-abi\fP\&.

.UNINDENT

.SS Target Selection Options

.sp

Clang fully supports cross compilation as an inherent part of its design.

Depending on how your version of Clang is configured, it may have support for a

number of cross compilers, or may only support a native target.

.INDENT 0.0

.TP

.B \-arch <architecture>

Specify the architecture to build for.

.UNINDENT

.INDENT 0.0

.TP

.B \-mmacosx\-version\-min=<version>

When building for Mac OS X, specify the minimum version supported by your

application.

.UNINDENT

.INDENT 0.0

.TP

.B \-miphoneos\-version\-min

When building for iPhone OS, specify the minimum version supported by your

application.

.UNINDENT

.INDENT 0.0

.TP

.B \-march=<cpu>

Specify that Clang should generate code for a specific processor family

member and later.  For example, if you specify \-march=i486, the compiler is

allowed to generate instructions that are valid on i486 and later processors,

but which may not exist on earlier ones.

.UNINDENT

.SS Code Generation Options

.INDENT 0.0

.TP

.B \-O0, \-O1, \-O2, \-O3, \-Ofast, \-Os, \-Oz, \-O, \-O4

Specify which optimization level to use:

.INDENT 7.0

.INDENT 3.5

\fI\%\-O0\fP Means "no optimization": this level compiles the fastest and

generates the most debuggable code.

.sp

\fI\%\-O1\fP Somewhere between \fI\%\-O0\fP and \fI\%\-O2\fP\&.

.sp

\fI\%\-O2\fP Moderate level of optimization which enables most

optimizations.

.sp

\fI\%\-O3\fP Like \fI\%\-O2\fP, except that it enables optimizations that

take longer to perform or that may generate larger code (in an attempt to

make the program run faster).

.sp

\fI\%\-Ofast\fP Enables all the optimizations from \fI\%\-O3\fP along

with other aggressive optimizations that may violate strict compliance with

language standards.

.sp

\fI\%\-Os\fP Like \fI\%\-O2\fP with extra optimizations to reduce code

size.

.sp

\fI\%\-Oz\fP Like \fI\%\-Os\fP (and thus \fI\%\-O2\fP), but reduces code

size further.

.sp

\fI\%\-O\fP Equivalent to \fI\%\-O2\fP\&.

.sp

\fI\%\-O4\fP and higher

.INDENT 0.0

.INDENT 3.5

Currently equivalent to \fI\%\-O3\fP

.UNINDENT

.UNINDENT

.UNINDENT

.UNINDENT

.UNINDENT

.INDENT 0.0

.TP

.B \-g

Generate debug information.  Note that Clang debug information works best at \-O0.

.UNINDENT

.INDENT 0.0

.TP

.B \-gmodules

Generate debug information that contains external references to

types defined in clang modules or precompiled headers instead of

emitting redundant debug type information into every object file.

This option implies \fB\-fmodule\-format=obj\fP\&.

.sp

This option should not be used when building static libraries for

distribution to other machines because the debug info will contain

references to the module cache on the machine the object files in

the library were built on.

.UNINDENT

.INDENT 0.0

.TP

.B \-fstandalone\-debug \-fno\-standalone\-debug

Clang supports a number of optimizations to reduce the size of debug

information in the binary. They work based on the assumption that the

debug type information can be spread out over multiple compilation units.

For instance, Clang will not emit type definitions for types that are not

needed by a module and could be replaced with a forward declaration.

Further, Clang will only emit type info for a dynamic C++ class in the

module that contains the vtable for the class.

.sp

The \fB\-fstandalone\-debug\fP option turns off these optimizations.

This is useful when working with 3rd\-party libraries that don\(aqt come with

debug information.  This is the default on Darwin.  Note that Clang will

never emit type information for types that are not referenced at all by the

program.

.UNINDENT

.INDENT 0.0

.TP

.B \-fexceptions

Enable generation of unwind information. This allows exceptions to be thrown

through Clang compiled stack frames.  This is on by default in x86\-64.

.UNINDENT

.INDENT 0.0

.TP

.B \-ftrapv

Generate code to catch integer overflow errors.  Signed integer overflow is

undefined in C. With this flag, extra code is generated to detect this and

abort when it happens.

.UNINDENT

.INDENT 0.0

.TP

.B \-fvisibility

This flag sets the default visibility level.

.UNINDENT

.INDENT 0.0

.TP

.B \-fcommon

This flag specifies that variables without initializers get common linkage.

It can be disabled with \fB\-fno\-common\fP\&.

.UNINDENT

.INDENT 0.0

.TP

.B \-ftls\-model=<model>

Set the default thread\-local storage (TLS) model to use for thread\-local

variables. Valid values are: "global\-dynamic", "local\-dynamic",

"initial\-exec" and "local\-exec". The default is "global\-dynamic". The default

model can be overridden with the tls_model attribute. The compiler will try

to choose a more efficient model if possible.

.UNINDENT

.INDENT 0.0

.TP

.B \-flto, \-emit\-llvm

Generate output files in LLVM formats, suitable for link time optimization.

When used with \fI\%\-S\fP this generates LLVM intermediate language

assembly files, otherwise this generates LLVM bitcode format object files

(which may be passed to the linker depending on the stage selection options).

.UNINDENT

.SS Driver Options

.INDENT 0.0

.TP

.B \-###

Print (but do not run) the commands to run for this compilation.

.UNINDENT

.INDENT 0.0

.TP

.B \-\-help

Display available options.

.UNINDENT

.INDENT 0.0

.TP

.B \-Qunused\-arguments

Do not emit any warnings for unused driver arguments.

.UNINDENT

.INDENT 0.0

.TP

.B \-Wa,<args>

Pass the comma separated arguments in args to the assembler.

.UNINDENT

.INDENT 0.0

.TP

.B \-Wl,<args>

Pass the comma separated arguments in args to the linker.

.UNINDENT

.INDENT 0.0

.TP

.B \-Wp,<args>

Pass the comma separated arguments in args to the preprocessor.

.UNINDENT

.INDENT 0.0

.TP

.B \-Xanalyzer <arg>

Pass arg to the static analyzer.

.UNINDENT

.INDENT 0.0

.TP

.B \-Xassembler <arg>

Pass arg to the assembler.

.UNINDENT

.INDENT 0.0

.TP

.B \-Xlinker <arg>

Pass arg to the linker.

.UNINDENT

.INDENT 0.0

.TP

.B \-Xpreprocessor <arg>

Pass arg to the preprocessor.

.UNINDENT

.INDENT 0.0

.TP

.B \-o <file>

Write output to file.

.UNINDENT

.INDENT 0.0

.TP

.B \-print\-file\-name=<file>

Print the full library path of file.

.UNINDENT

.INDENT 0.0

.TP

.B \-print\-libgcc\-file\-name

Print the library path for "libgcc.a".

.UNINDENT

.INDENT 0.0

.TP

.B \-print\-prog\-name=<name>

Print the full program path of name.

.UNINDENT

.INDENT 0.0

.TP

.B \-print\-search\-dirs

Print the paths used for finding libraries and programs.

.UNINDENT

.INDENT 0.0

.TP

.B \-save\-temps

Save intermediate compilation results.

.UNINDENT

.INDENT 0.0

.TP

.B \-integrated\-as, \-no\-integrated\-as

Used to enable and disable, respectively, the use of the integrated

assembler. Whether the integrated assembler is on by default is target

dependent.

.UNINDENT

.INDENT 0.0

.TP

.B \-time

Time individual commands.

.UNINDENT

.INDENT 0.0

.TP

.B \-ftime\-report

Print timing summary of each stage of compilation.

.UNINDENT

.INDENT 0.0

.TP

.B \-v

Show commands to run and use verbose output.

.UNINDENT

.SS Diagnostics Options

.INDENT 0.0

.TP

.B \-fshow\-column, \-fshow\-source\-location, \-fcaret\-diagnostics, \-fdiagnostics\-fixit\-info, \-fdiagnostics\-parseable\-fixits, \-fdiagnostics\-print\-source\-range\-info, \-fprint\-source\-range\-info, \-fdiagnostics\-show\-option, \-fmessage\-length

These options control how Clang prints out information about diagnostics

(errors and warnings). Please see the Clang User\(aqs Manual for more information.

.UNINDENT

.SS Preprocessor Options

.INDENT 0.0

.TP

.B \-D<macroname>=<value>

Adds an implicit #define into the predefines buffer which is read before the

source file is preprocessed.

.UNINDENT

.INDENT 0.0

.TP

.B \-U<macroname>

Adds an implicit #undef into the predefines buffer which is read before the

source file is preprocessed.

.UNINDENT

.INDENT 0.0

.TP

.B \-include <filename>

Adds an implicit #include into the predefines buffer which is read before the

source file is preprocessed.

.UNINDENT

.INDENT 0.0

.TP

.B \-I<directory>

Add the specified directory to the search path for include files.

.UNINDENT

.INDENT 0.0

.TP

.B \-F<directory>

Add the specified directory to the search path for framework include files.

.UNINDENT

.INDENT 0.0

.TP

.B \-nostdinc

Do not search the standard system directories or compiler builtin directories

for include files.

.UNINDENT