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<html>
<head>
<title>Clang Compiler User's Manual</title>
<link type="text/css" rel="stylesheet" href="../menu.css" />
<link type="text/css" rel="stylesheet" href="../content.css" />
<style type="text/css">
td {
vertical-align: top;
}
</style>
</head>
<body>
<!--#include virtual="../menu.html.incl"-->
<div id="content">
<h1>Clang Compiler User's Manual</h1>
<ul>
<li><a href="#intro">Introduction</a>
<ul>
<li><a href="#terminology">Terminology</a></li>
<li><a href="#basicusage">Basic Usage</a></li>
</ul>
</li>
<li><a href="#commandline">Command Line Options</a>
<ul>
<li><a href="#cl_diagnostics">Options to Control Error and Warning
Messages</a></li>
</ul>
</li>
<li><a href="#general_features">Language and Target-Independent Features</a>
<ul>
<li><a href="#diagnostics">Controlling Errors and Warnings</a></li>
<li><a href="#precompiledheaders">Precompiled Headers</a></li>
</ul>
</li>
<li><a href="#c">C Language Features</a>
<ul>
<li><a href="#c_ext">Extensions supported by clang</a></li>
<li><a href="#c_modes">Differences between various standard modes</a></li>
<li><a href="#c_unimpl_gcc">GCC extensions not implemented yet</a></li>
<li><a href="#c_unsupp_gcc">Intentionally unsupported GCC extensions</a></li>
<li><a href="#c_ms">Microsoft extensions</a></li>
</ul>
</li>
<li><a href="#objc">Objective-C Language Features</a>
<ul>
<li><a href="#objc_incompatibilities">Intentional Incompatibilities with
GCC</a></li>
</ul>
</li>
<li><a href="#cxx">C++ Language Features</a>
<ul>
<li>...</li>
</ul>
</li>
<li><a href="#objcxx">Objective C++ Language Features</a>
<ul>
<li>...</li>
</ul>
</li>
<li><a href="#target_features">Target-Specific Features and Limitations</a>
<ul>
<li><a href="#target_arch">CPU Architectures Features and Limitations</a>
<ul>
<li><a href="#target_arch_x86">X86</a></li>
<li>PPC</li>
<li>ARM</li>
</ul>
</li>
<li><a href="#target_os">Operating System Features and Limitations</a>
<ul>
<li><a href="#target_os_darwin">Darwin (Mac OS/X)</a></li>
<li>Linux, etc.</li>
</ul>
</li>
</ul>
</li>
</ul>
<!-- ======================================================================= -->
<h2 id="intro">Introduction</h2>
<!-- ======================================================================= -->
<p>The Clang Compiler is an open-source compiler for the C family of programming
languages, aiming to be the best in class implementation of these languages.
Clang builds on the LLVM optimizer and code generator, allowing it to provide
high-quality optimization and code generation support for many targets. For
more general information, please see the <a href="http://clang.llvm.org">Clang
Web Site</a> or the <a href="http://llvm.org">LLVM Web Site</a>.</p>
<p>This document describes important notes about using Clang as a compiler for
an end-user, documenting the supported features, command line options, etc. If
you are interested in using Clang to build a tool that processes code, please
see <a href="InternalsManual.html">the Clang Internals Manual</a>. If you are
interested in the <a href="http://clang.llvm.org/StaticAnalysis.html">Clang
Static Analyzer</a>, please see its web page.</p>
<p>Clang is designed to support the C family of programming languages, which
includes <a href="#c">C</a>, <a href="#objc">Objective-C</a>, <a
href="#cxx">C++</a>, and <a href="#objcxx">Objective-C++</a> as well as many
dialects of those. For language-specific information, please see the
corresponding language specific section:</p>
<ul>
<li><a href="#c">C Language</a>: K&R C, ANSI C89, ISO C90, ISO C94
(C89+AMD1), ISO C99 (+TC1, TC2, TC3). </li>
<li><a href="#objc">Objective-C Language</a>: ObjC 1, ObjC 2, ObjC 2.1, plus
variants depending on base language.</li>
<li><a href="#cxx">C++ Language Features</a></li>
<li><a href="#objcxx">Objective C++ Language</a></li>
</ul>
<p>In addition to these base languages and their dialects, Clang supports a
broad variety of language extensions, which are documented in the corresponding
language section. These extensions are provided to be compatible with the GCC,
Microsoft, and other popular compilers as well as to improve functionality
through Clang-specific features. The Clang driver and language features are
intentionally designed to be as compatible with the GNU GCC compiler as
reasonably possible, easing migration from GCC to Clang. In most cases, code
"just works".</p>
<p>In addition to language specific features, Clang has a variety of features
that depend on what CPU architecture or operating system is being compiled for.
Please see the <a href="target_features">Target-Specific Features and
Limitations</a> section for more details.</p>
<p>The rest of the introduction introduces some basic <a
href="#terminology">compiler terminology</a> that is used throughout this manual
and contains a basic <a href="#basicusage">introduction to using Clang</a>
as a command line compiler.</p>
<!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = -->
<h3 id="terminology">Terminology</h3>
<!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = -->
<p>Front end, parser, backend, preprocessor, undefined behavior, diagnostic,
optimizer</p>
<!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = -->
<h3 id="basicusage">Basic Usage</h3>
<!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = -->
<p>Intro to how to use a C compiler for newbies.</p>
<p>
compile + link
compile then link
debug info
enabling optimizations
picking a language to use, defaults to C99 by default. Autosenses based on
extension.
using a makefile
</p>
<!-- ======================================================================= -->
<h2 id="commandline">Command Line Options</h2>
<!-- ======================================================================= -->
<p>
This section is generally an index into other sections. It does not go into
depth on the ones that are covered by other sections. However, the first part
introduces the language selection and other high level options like -c, -g, etc.
</p>
<!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = -->
<h3 id="cl_diagnostics">Options to Control Error and Warning Messages</h3>
<!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = -->
<p><b>-Werror</b>: Turn warnings into errors.</p>
<p><b>-Werror=foo</b>: Turn warning "foo" into an error.</p>
<p><b>-Wno-error=foo</b>: Turn warning "foo" into an warning even if -Werror is
specified.</p>
<p><b>-Wfoo</b>: Enable warning foo</p>
<p><b>-Wno-foo</b>: Disable warning foo</p>
<p><b>-w</b>: Disable all warnings.</p>
<p><b>-pedantic</b>: Warn on language extensions.</p>
<p><b>-pedantic-errors</b>: Error on language extensions.</p>
<p><b>-Wsystem-headers</b>: Enable warnings from system headers.</p>
<!-- ================================================= -->
<h4 id="cl_diag_formatting">Formatting of Diagnostics</h4>
<!-- ================================================= -->
<p>Clang aims to produce beautiful diagnostics by default, particularly for new
users that first come to Clang. However, different people have different
preferences, and sometimes Clang is driven by another program that wants to
parse simple and consistent output, not a person. For these cases, Clang
provides a wide range of options to control the exact output format of the
diagnostics that it generates.</p>
<dl>
<!-- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -->
<dt id="opt_fshow-column"><b>-f[no-]show-column</b>: Print column number in
diagnostic.</dt>
<dd>This option, which defaults to on, controls whether or not Clang prints the
column number of a diagnostic. For example, when this is enabled, Clang will
print something like:</p>
<pre>
test.c:28:8: warning: extra tokens at end of #endif directive [-Wextra-tokens]
#endif bad
^
//
</pre>
<p>When this is disabled, Clang will print "test.c:28: warning..." with no
column number.</p>
</dd>
<!-- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -->
<dt id="opt_fshow-source-location"><b>-f[no-]show-source-location</b>: Print
source file/line/column information in diagnostic.</dt>
<dd>This option, which defaults to on, controls whether or not Clang prints the
filename, line number and column number of a diagnostic. For example,
when this is enabled, Clang will print something like:</p>
<pre>
test.c:28:8: warning: extra tokens at end of #endif directive [-Wextra-tokens]
#endif bad
^
//
</pre>
<p>When this is disabled, Clang will not print the "test.c:28:8: " part.</p>
</dd>
<!-- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -->
<dt id="opt_fcaret-diagnostics"><b>-f[no-]caret-diagnostics</b>: Print source
line and ranges from source code in diagnostic.</dt>
<dd>This option, which defaults to on, controls whether or not Clang prints the
source li
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