llvm-project/clang/docs/tools/clang.pod

=pod

=head1 NAME

clang - the Clang C and Objective-C compiler

=head1 SYNOPSIS

B<clang> [B<-c>|B<-S>|B<-E>] B<-std=>I<standard> B<-g>
  [B<-O0>|B<-O1>|B<-O2>|B<-Os>|B<-O3>|B<-O4>]
  B<-W>I<warnings...> B<-pedantic>
  B<-I>I<dir...> B<-L>I<dir...>
  B<-D>I<macro[=defn]>
  B<-f>I<feature-option...>
  B<-m>I<machine-option...>
  B<-o> I<output-file>
  I<input-filenames>

=head1 DESCRIPTION

B<clang> is a 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:

=over

=item B<Driver>

The B<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.

=item 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) or ".mi" (for Objective-C) file.

=item B<Parsing and Semantic Analysis>

This stage parses the input file, translating preprocessor tokens into a parse
tree.  Once in the form of a parser 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).

=item B<Code Generation and Optimization>

This stage translates an AST into low-level intermediate code (known as "LLVM
IR") and ultimately to machine code (depending on the optimization level).  This
phase is responsible for optimizing the generated code and handling
target-specfic code generation.  The output of this stage is typically called a
".s" file or "assembly" file.

=item 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.

=item 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.

=back

The Clang compiler supports a large number of options to control each of these
stages.  In addition to compilation of code, Clang also supports other tools:

B<Clang Static Analyzer>

The Clang Static Analyzer is a tool that scans source code to try to find bugs
though code analysis.  This tool uses many parts of Clang and is built into the
same driver.


=head1 OPTIONS

=head2 Stage Selection Options

=over

=item B<-E>

Run the preprocessor stage.

=item B<-fsyntax-only>

Run the preprocessor, parser and type checking stages.

=item B<-emit-llvm>

Run the preprocessor, parser, type checking stages, LLVM generation and
optimization stages.

=item B<-S>

Run all of the above, plus target-specific code generation, producing an
assembly file.

=item B<-c>

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

=item 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.

=item B<--analyze>

Run the Clang Static Analyzer.

=back



=head2 Driver Options

=over

=item B<-###>

Print the commands to run for this compilation.

=item B<--help>

Display available options.

=item B<-Qunused-arguments>

Don't emit warning for unused driver arguments.

=item B<-Wa,>I<args>

Pass the comma separated arguments in I<args> to the assembler.

=item B<-Wl,>I<args>

Pass the comma separated arguments in I<args> to the linker.

=item B<-Wp,>I<args>

Pass the comma separated arguments in I<args> to the preprocessor.

=item B<-Xanalyzer> I<arg>

Pass I<arg> to the static analyzer.

=item B<-Xassembler> I<arg>

Pass I<arg> to the assembler.

=item B<-Xclang> I<arg>

Pass I<arg> to the clang compiler.

=item B<-Xlinker> I<arg>

Pass I<arg> to the linker.

=item B<-Xpreprocessor> I<arg>

Pass I<arg> to the preprocessor.

=item B<-o> I<file>               

Write output to I<file>.

=item B<-print-file-name>=I<file>

Print the full library path of I<file>.

=item B<-print-libgcc-file-name>

Print the library path for "libgcc.a".

=item B<-print-prog-name>=I<name>

Print the full program path of I<name>.

=item B<-print-search-dirs>

Print the paths used for finding libraries and programs.

=item B<-save-temps>

Save intermediate compilation results.

=item B<-time>

Time individual commands.

=item B<-ftime-report>

Print timing summary of each stage of compilation.

=item B<-v>

Show commands to run and use verbose output.

=back



=head2 Target Selection Options

=over

-triple
-arch
-mmacosx-version-min=10.3.9
-miphoneos-version-min


=back



=head2 Language Selection and Mode Options

=over

=item B<-x> I<language>

Treat subsequent input files as having type I<language>.

=item B<-ObjC++>

Treat source input files as Objective-C++ inputs.

=item B<-ObjC>

Treat source input files as Objective-C inputs.

B<-std>=I<language>


-ffreestanding
-fno-builtin
-fmath-errno
-fobjc-gc-only
-fobjc-gc
-fpascal-strings
-fms-extensions
-fwritable-strings
-fno-lax-vector-conversions
-fblocks
-trigraphs


=back



=head2 Code Generation Options

=over

-fexceptions
-fobjc-nonfragile-abi
-fgnu-runtime
-fnext-runtime
-ftrapv
-fvisibility
-Os, O0, O1, O2, O3, O4
-fno-common
-g
-mcpu

=back




=head2 Diagnostics Options

=over

-fshow-column
-fshow-source-location
-fcaret-diagnostics
-fdiagnostics-fixit-info
-fdiagnostics-print-source-range-info
-fprint-source-range-info
-fdiagnostics-show-option
-fmessage-length


=back


=head2 Preprocessor Options

=over

=item B<-xyz>

Frob

-D
-U
-include
-imacros



-nostdinc
-F
-I
-idirafter
-iquote
-isystem
-iprefix
-iwithprefix
-iwithprefixbefore
-isysroot




=back




=head2 Parser and Semantic Analysis Options

=over

=back





=head2 Code Generation and Optimization Options

=over

=back






=head2 Assembler Options

=over

=back






=head2 Linker Options

=over

=back





=head2 Static Analyzer Options

=over

=back



=head1 ENVIRONMENT

=over

=item B<TMPDIR>, B<TEMP>, B<TMP>

These environment variables are checked, in order, for the location to
write temporary files used during the compilation process.

=item B<CPATH>

If this environment variable is present, it is treated as a delimited
list of paths to be added to the default system include path list. The
delimiter is the platform dependent delimitor, as used in the I<PATH>
environment variable.

Empty components in the environment variable are ignored.

=item B<C_INCLUDE_PATH>, B<OBJC_INCLUDE_PATH>, B<CPLUS_INCLUDE_PATH>,
B<OBJCPLUS_INCLUDE_PATH>

These environment variables specify additional paths, as for CPATH,
which are only used when processing the appropriate language.

=item B<MACOSX_DEPLOYMENT_TARGET>

If -mmacosx-version-min is unspecified, the default deployment target
is read from this environment variable.  This option only affects darwin
targets.

=back

=head1 BUGS

Clang currently does not have C++ support, and this manual page is incomplete.
To report bugs, please visit L<http://llvm.org/bugs/>.  Most bug reports should
include preprocessed source files (use the B<-E> option) and the full output of 
the compiler, along with information to reproduce.

=head1 SEE ALSO

 as(1), ld(1)

=head1 AUTHOR

Maintained by the Clang / LLVM Team (L<http://clang.llvm.org>).

=cut