path: root/static/freebsd/man9/cdefs.9 3.html

<table class="head">
  <tr>
    <td class="head-ltitle">CDEFS(9)</td>
    <td class="head-vol">Kernel Developer's Manual</td>
    <td class="head-rtitle">CDEFS(9)</td>
  </tr>
</table>
<div class="manual-text">
<section class="Sh">
<h1 class="Sh" id="NAME"><a class="permalink" href="#NAME">NAME</a></h1>
<p class="Pp"><code class="Nm">cdefs</code> &#x2014; <span class="Nd">compiler
    portability macro definitions</span></p>
</section>
<section class="Sh">
<h1 class="Sh" id="DESCRIPTION"><a class="permalink" href="#DESCRIPTION">DESCRIPTION</a></h1>
<p class="Pp"><code class="In">&lt;<a class="In">sys/cdefs.h</a>&gt;</code>
    defines macros for compiler, C language standard portability, POSIX
    standards compliance and symbol visibility. It defines programming
    interfaces for the system header files to adopt to the many environments
    <span class="Ux">FreeBSD</span> supports compilation for. It defines
    convenience macros for the <span class="Ux">FreeBSD</span> sources, tailored
    to the base system's needs.</p>
<p class="Pp">Most of these macros are for use inside the
    <span class="Ux">FreeBSD</span> sources only. They are not intended as a
    general portability layer.</p>
</section>
<section class="Sh">
<h1 class="Sh" id="Supported_Compilers"><a class="permalink" href="#Supported_Compilers">Supported
  Compilers</a></h1>
<div class="Bd-indent">
<dl class="Bl-tag">
  <dt>Compilers supported for building programs on
    <span class="Ux">FreeBSD</span>:</dt>
  <dd>
    <table class="Bl-column Bd-indent">
      <tr id="Compiler">
        <td><a class="permalink" href="#Compiler"><b class="Sy">Compiler</b></a></td>
        <td><a class="permalink" href="#Versions"><b class="Sy" id="Versions">Versions</b></a></td>
      </tr>
      <tr>
        <td>gcc</td>
        <td>9, 10, 11, 12, 13, 14</td>
      </tr>
      <tr>
        <td>clang</td>
        <td>10, 11, 12, 13, 14, 15, 16, 17, 18</td>
      </tr>
      <tr>
        <td>TinyC (tcc)</td>
        <td>0.9</td>
      </tr>
      <tr>
        <td>pcc</td>
        <td>1.1</td>
      </tr>
    </table>
    <p class="Pp">Due to testing constraints, tcc and pcc may not always
      work.</p>
  </dd>
  <dt>Compilers supported for building <span class="Ux">FreeBSD
    itself:</span></dt>
  <dd>
    <table class="Bl-column Bd-indent">
      <tr id="Compiler~2">
        <td><a class="permalink" href="#Compiler~2"><b class="Sy">Compiler</b></a></td>
        <td><a class="permalink" href="#Major"><b class="Sy" id="Major">Major
          Versions Supported</b></a></td>
      </tr>
      <tr>
        <td>gcc</td>
        <td>12, 13, 14</td>
      </tr>
      <tr>
        <td>clang</td>
        <td>16, 17, 18</td>
      </tr>
    </table>
    <p class="Pp">Please note: Not every single minor versions of these
        compilers will work or are supported.</p>
  </dd>
</dl>
</div>
</section>
<section class="Sh">
<h1 class="Sh" id="Macros_and_Magic_for_Programming_Environment"><a class="permalink" href="#Macros_and_Magic_for_Programming_Environment">Macros
  and Magic for Programming Environment</a></h1>
<p class="Pp"><code class="Nm">cdefs</code> defines (or refrains from defining)
    a number of macros to increase portability of compiled programs. These are
    to allow more advanced language features to appear in header files. The
    header files assume a compiler that accepts C prototype function
    declarations. They also assume that the compiler accepts ANSI C89 keywords
    for all language dialects.</p>
<section class="Ss">
<h2 class="Ss" id="General_Macros"><a class="permalink" href="#General_Macros">General
  Macros</a></h2>
<p class="Pp">General macros that facilitate multiple language environments and
    language dialects.</p>
<table class="Bl-column">
  <tr id="Macro">
    <td><a class="permalink" href="#Macro"><b class="Sy">Macro</b></a></td>
    <td><a class="permalink" href="#Description"><b class="Sy" id="Description">Description</b></a></td>
  </tr>
  <tr id="__volatile">
    <td><a class="permalink" href="#__volatile"><code class="Dv">__volatile</code></a></td>
    <td>expands to volatile in C++ and C89 and newer environments, __volatile in
      pre-ANSI environments that support this extension or nothing
      otherwise.</td>
  </tr>
  <tr id="__inline">
    <td><a class="permalink" href="#__inline"><code class="Dv">__inline</code></a></td>
    <td>expands to inline in C++ and C89 and newer environments, __inline in
      pre-ANSI environments that support this extension or nothing
      otherwise.</td>
  </tr>
  <tr id="__restrict">
    <td><a class="permalink" href="#__restrict"><code class="Dv">__restrict</code></a></td>
    <td>expands to restrict in C99 and newer environments, or __restrict
      otherwise.</td>
  </tr>
  <tr id="__CONCAT">
    <td><a class="permalink" href="#__CONCAT"><code class="Dv">__CONCAT</code></a></td>
    <td>used to paste two pre-processor tokens.</td>
  </tr>
  <tr id="__STRING">
    <td><a class="permalink" href="#__STRING"><code class="Dv">__STRING</code></a></td>
    <td>used to convert the argument to a string.</td>
  </tr>
  <tr id="__BEGIN_DECLS">
    <td><a class="permalink" href="#__BEGIN_DECLS"><code class="Dv">__BEGIN_DECLS</code></a></td>
    <td>Start a group of functions.</td>
  </tr>
  <tr id="__END_DECLS">
    <td><a class="permalink" href="#__END_DECLS"><code class="Dv">__END_DECLS</code></a></td>
    <td>End a group of functions. In a C environment, these are defined as
      nothing. In a C++ environment, these declare the functions to have
      &#x201C;C&#x201D; linkage.</td>
  </tr>
</table>
</section>
<section class="Ss">
<h2 class="Ss" id="Function,_Structure_and_Variable_Modifiers"><a class="permalink" href="#Function,_Structure_and_Variable_Modifiers">Function,
  Structure and Variable Modifiers</a></h2>
<table class="Bl-column">
  <tr id="Macro~2">
    <td><a class="permalink" href="#Macro~2"><b class="Sy">Macro</b></a></td>
    <td><a class="permalink" href="#Description~2"><b class="Sy" id="Description~2">Description</b></a></td>
  </tr>
  <tr id="__weak_symbol">
    <td><a class="permalink" href="#__weak_symbol"><b class="Sy">__weak_symbol</b></a></td>
    <td>Declare the symbol to be a weak symbol</td>
  </tr>
  <tr id="__dead2">
    <td><a class="permalink" href="#__dead2"><b class="Sy">__dead2</b></a></td>
    <td>Function will not return</td>
  </tr>
  <tr id="__pure2">
    <td><a class="permalink" href="#__pure2"><b class="Sy">__pure2</b></a></td>
    <td>Function has no side effects</td>
  </tr>
  <tr id="__unused">
    <td><a class="permalink" href="#__unused"><b class="Sy">__unused</b></a></td>
    <td>To Variable may be unused (usually arguments), so do not warn about
      it</td>
  </tr>
  <tr id="__used">
    <td><a class="permalink" href="#__used"><b class="Sy">__used</b></a></td>
    <td>Function really is used, so emit it even if it appears unused.</td>
  </tr>
  <tr id="__deprecated">
    <td><a class="permalink" href="#__deprecated"><b class="Sy">__deprecated</b></a></td>
    <td>Function interface has been deprecated, and clients should migrate to a
      new interface. A warning will be issued for clients of this
      interface.</td>
  </tr>
  <tr id="__deprecated1(msg)">
    <td><a class="permalink" href="#__deprecated1(msg)"><b class="Sy">__deprecated1(msg)</b></a></td>
    <td>Function interface has been deprecated, and clients should migrate to a
      new interface. The string <var class="Fa">msg</var> will be included in a
      warning issued for clients of this interface.</td>
  </tr>
  <tr id="__packed">
    <td><a class="permalink" href="#__packed"><b class="Sy">__packed</b></a></td>
    <td>Do not have space between structure elements for natural alignment. Used
      when communicating with external protocols.</td>
  </tr>
  <tr id="__aligned(x)">
    <td><a class="permalink" href="#__aligned(x)"><b class="Sy">__aligned(x)</b></a></td>
    <td>Specify in bytes the minimum alignment for the specified field,
      structure or variable</td>
  </tr>
  <tr id="__section(x)">
    <td><a class="permalink" href="#__section(x)"><b class="Sy">__section(x)</b></a></td>
    <td>Place function or variable in section <var class="Fa">x</var></td>
  </tr>
  <tr id="__writeonly">
    <td><a class="permalink" href="#__writeonly"><b class="Sy">__writeonly</b></a></td>
    <td>Hint that the variable is only assigned to, but do not warn about it.
      Useful for macros and other places the eventual use of the result is
      unknown.</td>
  </tr>
  <tr id="__alloc_size(x)">
    <td><a class="permalink" href="#__alloc_size(x)"><b class="Sy">__alloc_size(x)</b></a></td>
    <td>The function always returns at least the number of bytes determined by
      argument number Fa x</td>
  </tr>
  <tr id="__alloc_size2(x,n)">
    <td><a class="permalink" href="#__alloc_size2(x,n)"><b class="Sy">__alloc_size2(x,n)</b></a></td>
    <td>The function always returns an array, whose size is at least the number
      of bytes determined by argument number Fa x times the number of elements
      specified by argument number Fa n</td>
  </tr>
  <tr id="__alloc_align(x)">
    <td><a class="permalink" href="#__alloc_align(x)"><b class="Sy">__alloc_align(x)</b></a></td>
    <td>Function either returns a pointer aligned to <var class="Fa">x
      bytes</var> or Dv NULL.</td>
  </tr>
  <tr id="__min_size">
    <td><a class="permalink" href="#__min_size"><b class="Sy">__min_size</b></a></td>
    <td>Declare the array to have a certain, minimum size</td>
  </tr>
  <tr id="__malloc_like">
    <td><a class="permalink" href="#__malloc_like"><b class="Sy">__malloc_like</b></a></td>
    <td>Function behaves like the &#x201C;malloc&#x201D; family of
      functions.</td>
  </tr>
  <tr id="__pure">
    <td><a class="permalink" href="#__pure"><b class="Sy">__pure</b></a></td>
    <td>Function has no side effects</td>
  </tr>
  <tr id="__always_inline">
    <td><a class="permalink" href="#__always_inline"><b class="Sy">__always_inline</b></a></td>
    <td>Always inline this function when called</td>
  </tr>
  <tr id="__fastcall">
    <td><a class="permalink" href="#__fastcall"><b class="Sy">__fastcall</b></a></td>
    <td>Use the &#x201C;fastcall&#x201D; ABI to call and name mangle this
      function.</td>
  </tr>
  <tr id="__result_use_check">
    <td><a class="permalink" href="#__result_use_check"><b class="Sy">__result_use_check</b></a></td>
    <td>Warn if function caller does not use its return value</td>
  </tr>
  <tr id="__nodiscard">
    <td><a class="permalink" href="#__nodiscard"><b class="Sy">__nodiscard</b></a></td>
    <td>Equivalent to the standard &#x201C;[[nodiscard]]&#x201D; attribute. If
      applied to a function, warn if function caller does not use its return
      value. The warning may be silenced using a cast to
      <var class="Vt">void</var>, or in C++, using an assignment to
      <var class="Va">std::ignore</var>. If applied to a struct, C++ class or
      enum, this applies to all functions returning values of that type. If
      applied to a C++ constructor, this applies to creating instances of the
      class using that constructor.</td>
  </tr>
  <tr id="__returns_twice">
    <td><a class="permalink" href="#__returns_twice"><b class="Sy">__returns_twice</b></a></td>
    <td>Returns multiple times, like <a class="Xr">fork(2)</a></td>
  </tr>
  <tr id="__unreachable">
    <td><a class="permalink" href="#__unreachable"><b class="Sy">__unreachable</b></a></td>
    <td>This code is not reachable at runtime</td>
  </tr>
  <tr id="__predict_true(x)">
    <td><a class="permalink" href="#__predict_true(x)"><b class="Sy">__predict_true(x)</b></a></td>
    <td>Hint to the compiler that <var class="Fa">x</var> is true most of the
      time. Should only be used when performance is improved for a frequently
      called bit of code.</td>
  </tr>
  <tr id="__predict_false(x)">
    <td><a class="permalink" href="#__predict_false(x)"><b class="Sy">__predict_false(x)</b></a></td>
    <td>Hint to the compiler that <var class="Fa">x</var> is false most of the
      time. Should only be used when performance is improved for a frequently
      called bit of code.</td>
  </tr>
  <tr id="__null_sentinel">
    <td><a class="permalink" href="#__null_sentinel"><b class="Sy">__null_sentinel</b></a></td>
    <td>The varadic function contains a parameter that is a NULL sentinel to
      mark the end of its arguments.</td>
  </tr>
  <tr id="__exported">
    <td><a class="permalink" href="#__exported"><b class="Sy">__exported</b></a></td>
    <td></td>
  </tr>
  <tr id="__hidden">
    <td><a class="permalink" href="#__hidden"><b class="Sy">__hidden</b></a></td>
    <td></td>
  </tr>
  <tr id="__printflike(fmtarg,firstvararg)">
    <td><a class="permalink" href="#__printflike(fmtarg,firstvararg)"><b class="Sy">__printflike(fmtarg,firstvararg)</b></a></td>
    <td>Function is similar to
      <a class="permalink" href="#printf"><code class="Fn" id="printf">printf</code></a>()
      which specifies the format argument with <var class="Fa">fmtarg</var> and
      where the arguments formatted by that format start with the
      <var class="Fa">firstvararg</var>, with 0 meaning that
      <code class="Dv">va_arg</code> is used and cannot be checked.</td>
  </tr>
  <tr id="__scanflike(fmtarg,firstvararg)">
    <td><a class="permalink" href="#__scanflike(fmtarg,firstvararg)"><b class="Sy">__scanflike(fmtarg,firstvararg)</b></a></td>
    <td>Function is similar to
      <a class="permalink" href="#scanf"><code class="Fn" id="scanf">scanf</code></a>()
      which specifies the format argument with <var class="Fa">fmtarg</var> and
      where the arguments formatted by that format start with the
      <var class="Fa">firstvararg</var>, with 0 meaning that
      <code class="Dv">va_arg</code> is used and cannot be checked.</td>
  </tr>
  <tr id="__format_arg(f)">
    <td><a class="permalink" href="#__format_arg(f)"><b class="Sy">__format_arg(f)</b></a></td>
    <td>Specifies that arg <var class="Fa">f</var> contains a string that will
      be passed to a function like <code class="Fn">printf</code>() or
      <var class="Fa">scanf</var> after being translated in some way.</td>
  </tr>
  <tr id="__strfmonlike(fmtarg,firstvararg)">
    <td><a class="permalink" href="#__strfmonlike(fmtarg,firstvararg)"><b class="Sy">__strfmonlike(fmtarg,firstvararg)</b></a></td>
    <td>Function is similar to <code class="Fn">scanf</code>() which specifies
      the format argument with <var class="Fa">fmtarg</var> and where the
      arguments formatted by that format start with the
      <var class="Fa">firstvararg</var>, with 0 meaning that
      <code class="Dv">va_arg</code> is used and cannot be checked.</td>
  </tr>
  <tr id="__strtimelike(fmtarg,firstvararg)">
    <td><a class="permalink" href="#__strtimelike(fmtarg,firstvararg)"><b class="Sy">__strtimelike(fmtarg,firstvararg)</b></a></td>
    <td>Function is similar to <code class="Fn">scanf</code>() which specifies
      the format argument with <var class="Fa">fmtarg</var> and where the
      arguments formatted by that format start with the
      <var class="Fa">firstvararg</var>, with 0 meaning that
      <code class="Dv">va_arg</code> is used and cannot be checked.</td>
  </tr>
  <tr id="__printf0like(fmtarg,firstvararg)">
    <td><a class="permalink" href="#__printf0like(fmtarg,firstvararg)"><b class="Sy">__printf0like(fmtarg,firstvararg)</b></a></td>
    <td>Exactly the same as
      <a class="permalink" href="#__printflike"><b class="Sy" id="__printflike">__printflike</b></a>
      except <var class="Fa">fmtarg</var> may be
      <code class="Dv">NULL.</code></td>
  </tr>
  <tr id="__strong_reference(sym,aliassym)">
    <td><a class="permalink" href="#__strong_reference(sym,aliassym)"><b class="Sy">__strong_reference(sym,aliassym)</b></a></td>
    <td></td>
  </tr>
  <tr id="__weak_reference(sym,alias)">
    <td><a class="permalink" href="#__weak_reference(sym,alias)"><b class="Sy">__weak_reference(sym,alias)</b></a></td>
    <td></td>
  </tr>
  <tr id="__warn_references(sym,msg)">
    <td><a class="permalink" href="#__warn_references(sym,msg)"><b class="Sy">__warn_references(sym,msg)</b></a></td>
    <td></td>
  </tr>
  <tr id="__sym_compat(sym,impl,verid)">
    <td><a class="permalink" href="#__sym_compat(sym,impl,verid)"><b class="Sy">__sym_compat(sym,impl,verid)</b></a></td>
    <td></td>
  </tr>
  <tr id="__sym_default(sym,impl,verid)">
    <td><a class="permalink" href="#__sym_default(sym,impl,verid)"><b class="Sy">__sym_default(sym,impl,verid)</b></a></td>
    <td></td>
  </tr>
  <tr id="__GLOBAL(sym)">
    <td><a class="permalink" href="#__GLOBAL(sym)"><b class="Sy">__GLOBAL(sym)</b></a></td>
    <td></td>
  </tr>
  <tr id="__WEAK(sym)">
    <td><a class="permalink" href="#__WEAK(sym)"><b class="Sy">__WEAK(sym)</b></a></td>
    <td></td>
  </tr>
  <tr id="__DECONST(type,var)">
    <td><a class="permalink" href="#__DECONST(type,var)"><b class="Sy">__DECONST(type,var)</b></a></td>
    <td></td>
  </tr>
  <tr id="__DEVOLATILE(type,var)">
    <td><a class="permalink" href="#__DEVOLATILE(type,var)"><b class="Sy">__DEVOLATILE(type,var)</b></a></td>
    <td></td>
  </tr>
  <tr id="__DEQUALIFY(type,var)">
    <td><a class="permalink" href="#__DEQUALIFY(type,var)"><b class="Sy">__DEQUALIFY(type,var)</b></a></td>
    <td></td>
  </tr>
  <tr id="__RENAME(x)">
    <td><a class="permalink" href="#__RENAME(x)"><b class="Sy">__RENAME(x)</b></a></td>
    <td></td>
  </tr>
  <tr id="__arg_type_tag">
    <td><a class="permalink" href="#__arg_type_tag"><b class="Sy">__arg_type_tag</b></a></td>
    <td></td>
  </tr>
  <tr id="__datatype_type_tag">
    <td><a class="permalink" href="#__datatype_type_tag"><b class="Sy">__datatype_type_tag</b></a></td>
    <td></td>
  </tr>
  <tr id="__align_up(x,y)">
    <td><a class="permalink" href="#__align_up(x,y)"><b class="Sy">__align_up(x,y)</b></a></td>
    <td></td>
  </tr>
  <tr id="__align_down(x,y)">
    <td><a class="permalink" href="#__align_down(x,y)"><b class="Sy">__align_down(x,y)</b></a></td>
    <td></td>
  </tr>
  <tr id="__is_aligned(x,y)">
    <td><a class="permalink" href="#__is_aligned(x,y)"><b class="Sy">__is_aligned(x,y)</b></a></td>
    <td></td>
  </tr>
</table>
</section>
<section class="Ss">
<h2 class="Ss" id="Locking_and_Debugging_Macros"><a class="permalink" href="#Locking_and_Debugging_Macros">Locking
  and Debugging Macros</a></h2>
<p class="Pp">Macros for lock annotation and debugging, as well as some general
    debugging macros for address sanitizers.</p>
<table class="Bl-column">
  <tr id="__lock_annotate(x)">
    <td><a class="permalink" href="#__lock_annotate(x)"><b class="Sy">__lock_annotate(x)</b></a></td>
    <td></td>
  </tr>
  <tr id="__lockable">
    <td><a class="permalink" href="#__lockable"><b class="Sy">__lockable</b></a></td>
    <td></td>
  </tr>
  <tr id="__locks_exclusive">
    <td><a class="permalink" href="#__locks_exclusive"><b class="Sy">__locks_exclusive</b></a></td>
    <td></td>
  </tr>
  <tr id="__locks_shared">
    <td><a class="permalink" href="#__locks_shared"><b class="Sy">__locks_shared</b></a></td>
    <td></td>
  </tr>
  <tr id="__trylocks_exclusive">
    <td><a class="permalink" href="#__trylocks_exclusive"><b class="Sy">__trylocks_exclusive</b></a></td>
    <td></td>
  </tr>
  <tr id="__trylocks_shared">
    <td><a class="permalink" href="#__trylocks_shared"><b class="Sy">__trylocks_shared</b></a></td>
    <td></td>
  </tr>
  <tr id="__unlocks">
    <td><a class="permalink" href="#__unlocks"><b class="Sy">__unlocks</b></a></td>
    <td></td>
  </tr>
  <tr id="__asserts_exclusive">
    <td><a class="permalink" href="#__asserts_exclusive"><b class="Sy">__asserts_exclusive</b></a></td>
    <td></td>
  </tr>
  <tr id="__asserts_shared">
    <td><a class="permalink" href="#__asserts_shared"><b class="Sy">__asserts_shared</b></a></td>
    <td></td>
  </tr>
  <tr id="__requires_exclusive">
    <td><a class="permalink" href="#__requires_exclusive"><b class="Sy">__requires_exclusive</b></a></td>
    <td></td>
  </tr>
  <tr id="__requires_shared">
    <td><a class="permalink" href="#__requires_shared"><b class="Sy">__requires_shared</b></a></td>
    <td></td>
  </tr>
  <tr id="__requires_unlocked">
    <td><a class="permalink" href="#__requires_unlocked"><b class="Sy">__requires_unlocked</b></a></td>
    <td></td>
  </tr>
  <tr id="__no_lock_analysis">
    <td><a class="permalink" href="#__no_lock_analysis"><b class="Sy">__no_lock_analysis</b></a></td>
    <td></td>
  </tr>
  <tr id="__nosanitizeaddress">
    <td><a class="permalink" href="#__nosanitizeaddress"><b class="Sy">__nosanitizeaddress</b></a></td>
    <td></td>
  </tr>
  <tr id="__nosanitizememory">
    <td><a class="permalink" href="#__nosanitizememory"><b class="Sy">__nosanitizememory</b></a></td>
    <td></td>
  </tr>
  <tr id="__nosanitizethread">
    <td><a class="permalink" href="#__nosanitizethread"><b class="Sy">__nosanitizethread</b></a></td>
    <td></td>
  </tr>
  <tr id="__nostackprotector">
    <td><a class="permalink" href="#__nostackprotector"><b class="Sy">__nostackprotector</b></a></td>
    <td></td>
  </tr>
  <tr id="__guarded_by(x)">
    <td><a class="permalink" href="#__guarded_by(x)"><b class="Sy">__guarded_by(x)</b></a></td>
    <td></td>
  </tr>
  <tr id="__pt_guarded_by(x)">
    <td><a class="permalink" href="#__pt_guarded_by(x)"><b class="Sy">__pt_guarded_by(x)</b></a></td>
    <td></td>
  </tr>
</table>
</section>
<section class="Ss">
<h2 class="Ss" id="Emulated_Keywords"><a class="permalink" href="#Emulated_Keywords">Emulated
  Keywords</a></h2>
<p class="Pp">As C evolves, many of the old macros we once used have been
    incorporated into the standard language. As this happens, we add support for
    these keywords as macros for older compilation environments. Sometimes this
    results in a nop in the older environment.</p>
<table class="Bl-column">
  <tr id="Keyword">
    <td><a class="permalink" href="#Keyword"><b class="Sy">Keyword</b></a></td>
    <td><a class="permalink" href="#Description~3"><b class="Sy" id="Description~3">Description</b></a></td>
  </tr>
  <tr id="_Alignas(x)">
    <td><a class="permalink" href="#_Alignas(x)"><b class="Sy">_Alignas(x)</b></a></td>
    <td></td>
  </tr>
  <tr id="_Alignof(x)">
    <td><a class="permalink" href="#_Alignof(x)"><b class="Sy">_Alignof(x)</b></a></td>
    <td></td>
  </tr>
  <tr id="_Noreturn">
    <td><a class="permalink" href="#_Noreturn"><b class="Sy">_Noreturn</b></a></td>
    <td>Expands to &#x201C;[[noreturn]]&#x201D; in C++-11 and newer compilation
      environments, otherwise &#x201C;__dead2&#x201D;</td>
  </tr>
  <tr id="_Static_assert(x,">
    <td><a class="permalink" href="#_Static_assert(x,"><b class="Sy">_Static_assert(x,
      y)</b></a></td>
    <td>Compile time assertion that <var class="Fa">x</var> is true, otherwise
      emit <var class="Fa">y</var> as the error message.</td>
  </tr>
  <tr id="_Thread_local">
    <td><a class="permalink" href="#_Thread_local"><b class="Sy">_Thread_local</b></a></td>
    <td>Designate variable as thread local storage</td>
  </tr>
  <tr id="__generic">
    <td><a class="permalink" href="#__generic"><b class="Sy">__generic</b></a></td>
    <td>implement _Generic-like features which aren't entirely possible to
      emulate the _Generic keyword</td>
  </tr>
  <tr id="__noexcept">
    <td><a class="permalink" href="#__noexcept"><b class="Sy">__noexcept</b></a></td>
    <td>to emulate the C++11 argument-less noexcept form</td>
  </tr>
  <tr id="__noexcept_if">
    <td><a class="permalink" href="#__noexcept_if"><b class="Sy">__noexcept_if</b></a></td>
    <td>to emulate the C++11 conditional noexcept form</td>
  </tr>
  <tr id="_Nonnull">
    <td><a class="permalink" href="#_Nonnull"><b class="Sy">_Nonnull</b></a></td>
    <td></td>
  </tr>
  <tr id="_Nullable">
    <td><a class="permalink" href="#_Nullable"><b class="Sy">_Nullable</b></a></td>
    <td></td>
  </tr>
  <tr id="_Null_unspecified">
    <td><a class="permalink" href="#_Null_unspecified"><b class="Sy">_Null_unspecified</b></a></td>
    <td></td>
  </tr>
</table>
</section>
<section class="Ss">
<h2 class="Ss" id="Support_Macros"><a class="permalink" href="#Support_Macros">Support
  Macros</a></h2>
<p class="Pp">The following macros are defined, or have specific values, to
    denote certain things about the build environment.</p>
<table class="Bl-column">
  <tr id="Macro~3">
    <td><a class="permalink" href="#Macro~3"><b class="Sy">Macro</b></a></td>
    <td><a class="permalink" href="#Description~4"><b class="Sy" id="Description~4">Description</b></a></td>
  </tr>
  <tr id="__LONG_LONG_SUPPORTED">
    <td><a class="permalink" href="#__LONG_LONG_SUPPORTED"><b class="Sy">__LONG_LONG_SUPPORTED</b></a></td>
    <td>Variables may be declared &#x201C;long long&#x201D;. This is defined for
      C99 or newer and C++ environments.</td>
  </tr>
  <tr id="__STDC_LIMIT_MACROS">
    <td><a class="permalink" href="#__STDC_LIMIT_MACROS"><b class="Sy">__STDC_LIMIT_MACROS</b></a></td>
    <td></td>
  </tr>
  <tr id="__STDC_CONSTANT_MACROS">
    <td><a class="permalink" href="#__STDC_CONSTANT_MACROS"><b class="Sy">__STDC_CONSTANT_MACROS</b></a></td>
    <td></td>
  </tr>
</table>
</section>
<section class="Ss">
<h2 class="Ss" id="Convenience_Macros"><a class="permalink" href="#Convenience_Macros">Convenience
  Macros</a></h2>
<p class="Pp">These macros make it easier to do a number of things, even though
    strictly speaking the standard places their normal form in another
  header.</p>
<table class="Bl-column">
  <tr id="Macro~4">
    <td><a class="permalink" href="#Macro~4"><b class="Sy">Macro</b></a></td>
    <td><a class="permalink" href="#Description~5"><b class="Sy" id="Description~5">Description</b></a></td>
  </tr>
  <tr id="__offsetof(type,field)">
    <td><a class="permalink" href="#__offsetof(type,field)"><b class="Sy">__offsetof(type,field)</b></a></td>
    <td></td>
  </tr>
  <tr id="__rangeof(type,start,end)">
    <td><a class="permalink" href="#__rangeof(type,start,end)"><b class="Sy">__rangeof(type,start,end)</b></a></td>
    <td></td>
  </tr>
  <tr id="__containerof(x,s,m)">
    <td><a class="permalink" href="#__containerof(x,s,m)"><b class="Sy">__containerof(x,s,m)</b></a></td>
    <td></td>
  </tr>
</table>
</section>
<section class="Ss">
<h2 class="Ss" id="ID_Strings"><a class="permalink" href="#ID_Strings">ID
  Strings</a></h2>
<p class="Pp">This section is deprecated, but is kept around because too much
    contrib software still uses these.</p>
<table class="Bl-column">
  <tr id="Macro~5">
    <td><a class="permalink" href="#Macro~5"><b class="Sy">Macro</b></a></td>
    <td><a class="permalink" href="#Description~6"><b class="Sy" id="Description~6">Description</b></a></td>
  </tr>
  <tr id="__IDSTRING(name,string)">
    <td><a class="permalink" href="#__IDSTRING(name,string)"><b class="Sy">__IDSTRING(name,string)</b></a></td>
    <td></td>
  </tr>
  <tr id="__FBSDID(s)">
    <td><a class="permalink" href="#__FBSDID(s)"><b class="Sy">__FBSDID(s)</b></a></td>
    <td></td>
  </tr>
  <tr id="__RCSID(s)">
    <td><a class="permalink" href="#__RCSID(s)"><b class="Sy">__RCSID(s)</b></a></td>
    <td></td>
  </tr>
  <tr id="__RCSID_SOURCE(s)">
    <td><a class="permalink" href="#__RCSID_SOURCE(s)"><b class="Sy">__RCSID_SOURCE(s)</b></a></td>
    <td></td>
  </tr>
  <tr id="__SCCSID(s)">
    <td><a class="permalink" href="#__SCCSID(s)"><b class="Sy">__SCCSID(s)</b></a></td>
    <td></td>
  </tr>
  <tr id="__COPYRIGHT(s)">
    <td><a class="permalink" href="#__COPYRIGHT(s)"><b class="Sy">__COPYRIGHT(s)</b></a></td>
    <td></td>
  </tr>
</table>
</section>
</section>
<section class="Sh">
<h1 class="Sh" id="Supported_C_Environments"><a class="permalink" href="#Supported_C_Environments">Supported
  C Environments</a></h1>
<p class="Pp"><span class="Ux">FreeBSD</span> supports a number C standard
    environments. Selection of the language dialect is a compiler-dependent
    command line option, though it is usually <code class="Fl">-std=XX</code>
    where XX is the standard to set for compiling, such as c89 or c23.
    <span class="Ux">FreeBSD</span> provides a number of selection macros to
    control visibility of symbols. Please see the section on Selection Macros
    for the specifics.</p>
<dl class="Bl-tag">
  <dt>K &amp; R</dt>
  <dd>Pre-ANSI Kernighan and Ritchie C. Sometimes called &#x201C;knr&#x201D; or
      &#x201C;C78&#x201D; to distinguish it from newer standards. Support for
      this compilation environment is dependent on compilers supporting this
      configuration. Most of the old forms of C have been deprecated or removed
      in. Compilers make compiling in this mode increasingly difficult and
      support for it may ultimately be removed from the tree.</dd>
  <dt id="__STDC__"><span class="St">ANSI X3.159-1989
    (&#x201C;ANSI&#x00A0;C89&#x201D;)</span></dt>
  <dd><a class="permalink" href="#__STDC__"><code class="Dv">__STDC__</code></a>
      is defined, however <code class="Dv">__STDC_VERSION__</code> is not.
    <p class="Pp">Strict environment selected with
        <code class="Dv">_ANSI_SOURCE</code>.</p>
  </dd>
  <dt id="__STDC_VERSION__"><span class="St">ISO/IEC 9899:1999
    (&#x201C;ISO&#x00A0;C99&#x201D;)</span></dt>
  <dd><a class="permalink" href="#__STDC_VERSION__"><code class="Dv">__STDC_VERSION__
      = 199901L</code></a>
    <p class="Pp">Strict environment selected with
        <code class="Dv">_C99_SOURCE</code>.</p>
  </dd>
  <dt id="__STDC_VERSION__~2"><span class="St">ISO/IEC 9899:2011
    (&#x201C;ISO&#x00A0;C11&#x201D;)</span></dt>
  <dd><a class="permalink" href="#__STDC_VERSION__~2"><code class="Dv">__STDC_VERSION__
      = 201112L</code></a>
    <p class="Pp">Strict environment selected with
        <code class="Dv">_C11_SOURCE</code>.</p>
  </dd>
  <dt id="__STDC_VERSION__~3">ISO/IEC 9899:2018 (&#x201C;ISO C17&#x201D;)</dt>
  <dd><a class="permalink" href="#__STDC_VERSION__~3"><code class="Dv">__STDC_VERSION__
      = 201710L</code></a>
    <p class="Pp">Strict environment selected with
        <code class="Dv">_C11_SOURCE</code> since there are no new C17 only
        symbols or macros.</p>
    <p class="Pp">This version of the standard did not introduce any new
        features, only made minor, technical corrections.</p>
  </dd>
  <dt id="__STDC_VERSION__~4"></dt>
  <dd><a class="permalink" href="#__STDC_VERSION__~4"><code class="Dv">__STDC_VERSION__
      = 202311L</code></a> Strict environment selected with
      <code class="Dv">_C23_SOURCE</code> though ISO C23 support is only
      partially implemented.</dd>
</dl>
<p class="Pp">For more information on C standards, see
  <a class="Xr">c(7)</a>.</p>
<section class="Ss">
<h2 class="Ss" id="Programming_Environment_Selection_Macros"><a class="permalink" href="#Programming_Environment_Selection_Macros">Programming
  Environment Selection Macros</a></h2>
<p class="Pp">Defining the macros outlined below requests that the system header
    files provide only the functions, structures and macros (symbols) defined by
    the appropriate standard, while suppressing all extensions. However, system
    headers not defined by that standard may define extensions. You may only
    define one of the following for any compilation unit.</p>
<table class="Bl-column">
  <tr id="Macro~6">
    <td><a class="permalink" href="#Macro~6"><b class="Sy">Macro</b></a></td>
    <td><a class="permalink" href="#Environment"><b class="Sy" id="Environment">Environment</b></a></td>
  </tr>
  <tr id="_POSIX_SOURCE">
    <td><a class="permalink" href="#_POSIX_SOURCE"><code class="Dv">_POSIX_SOURCE</code></a></td>
    <td><span class="St">IEEE Std 1003.1-1988 (&#x201C;POSIX.1&#x201D;)</span>
      including <span class="St">ANSI X3.159-1989
      (&#x201C;ANSI&#x00A0;C89&#x201D;)</span></td>
  </tr>
  <tr id="_POSIX_C_SOURCE">
    <td><a class="permalink" href="#_POSIX_C_SOURCE"><code class="Dv">_POSIX_C_SOURCE
      = 1</code></a></td>
    <td><span class="St">IEEE Std 1003.1-1988 (&#x201C;POSIX.1&#x201D;)</span>
      including <span class="St">ANSI X3.159-1989
      (&#x201C;ANSI&#x00A0;C89&#x201D;)</span></td>
  </tr>
  <tr id="_POSIX_C_SOURCE~2">
    <td><a class="permalink" href="#_POSIX_C_SOURCE~2"><code class="Dv">_POSIX_C_SOURCE
      = 2</code></a></td>
    <td><span class="St">IEEE Std 1003.1-1990 (&#x201C;POSIX.1&#x201D;)</span>
      including <span class="St">ANSI X3.159-1989
      (&#x201C;ANSI&#x00A0;C89&#x201D;)</span></td>
  </tr>
  <tr id="_POSIX_C_SOURCE~3">
    <td><a class="permalink" href="#_POSIX_C_SOURCE~3"><code class="Dv">_POSIX_C_SOURCE
      = 199309</code></a></td>
    <td><span class="St">IEEE Std 1003.1b-1993 (&#x201C;POSIX.1b&#x201D;)</span>
      including <span class="St">ANSI X3.159-1989
      (&#x201C;ANSI&#x00A0;C89&#x201D;)</span></td>
  </tr>
  <tr id="_POSIX_C_SOURCE~4">
    <td><a class="permalink" href="#_POSIX_C_SOURCE~4"><code class="Dv">_POSIX_C_SOURCE
      = 199506</code></a></td>
    <td><span class="St">IEEE Std 1003.1c-1995 (&#x201C;POSIX.1c&#x201D;)</span>
      including <span class="St">ANSI X3.159-1989
      (&#x201C;ANSI&#x00A0;C89&#x201D;)</span></td>
  </tr>
  <tr id="_POSIX_C_SOURCE~5">
    <td><a class="permalink" href="#_POSIX_C_SOURCE~5"><code class="Dv">_POSIX_C_SOURCE
      = 200112</code></a></td>
    <td><span class="St">IEEE Std 1003.1-2001 (&#x201C;POSIX.1&#x201D;)</span>
      including <span class="St">ISO/IEC 9899:1999
      (&#x201C;ISO&#x00A0;C99&#x201D;)</span></td>
  </tr>
  <tr id="_POSIX_C_SOURCE~6">
    <td><a class="permalink" href="#_POSIX_C_SOURCE~6"><code class="Dv">_POSIX_C_SOURCE
      = 200809</code></a></td>
    <td><span class="St">IEEE Std 1003.1-2008 (&#x201C;POSIX.1&#x201D;)</span>
      including <span class="St">ISO/IEC 9899:1999
      (&#x201C;ISO&#x00A0;C99&#x201D;)</span></td>
  </tr>
  <tr id="_POSIX_C_SOURCE~7">
    <td><a class="permalink" href="#_POSIX_C_SOURCE~7"><code class="Dv">_POSIX_C_SOURCE
      = 202405</code></a></td>
    <td>including ISO/IEC 9899:2018 (&quot;ISO C17&quot;),</td>
  </tr>
  <tr id="_XOPEN_SOURCE">
    <td><a class="permalink" href="#_XOPEN_SOURCE"><code class="Dv">_XOPEN_SOURCE
      defined</code></a></td>
    <td><span class="St">IEEE Std 1003.1-1990 (&#x201C;POSIX.1&#x201D;)</span>
      with XPG Extensions to <span class="St">Version&#x00A0;1 of the Single
      UNIX Specification (&#x201C;SUSv1&#x201D;)</span> including
      <span class="St">ANSI X3.159-1989
      (&#x201C;ANSI&#x00A0;C89&#x201D;)</span>. However,
      <span class="Ux">FreeBSD</span> implements this as a NOP because too much
      software breaks with the correct strict environment.</td>
  </tr>
  <tr id="_XOPEN_SOURCE~2">
    <td><a class="permalink" href="#_XOPEN_SOURCE~2"><code class="Dv">_XOPEN_SOURCE
      = 500</code></a></td>
    <td><span class="St">IEEE Std 1003.1c-1995 (&#x201C;POSIX.1c&#x201D;)</span>
      and XPG extensions to <span class="St">Version&#x00A0;2 of the Single UNIX
      Specification (&#x201C;SUSv2&#x201D;)</span> including
      <span class="St">ANSI X3.159-1989
      (&#x201C;ANSI&#x00A0;C89&#x201D;)</span></td>
  </tr>
  <tr id="_XOPEN_SOURCE~3">
    <td><a class="permalink" href="#_XOPEN_SOURCE~3"><code class="Dv">_XOPEN_SOURCE
      = 600</code></a></td>
    <td><span class="St">IEEE Std 1003.1-2001 (&#x201C;POSIX.1&#x201D;)</span>
      and XPG extensions to <span class="St">Version&#x00A0;3 of the Single UNIX
      Specification (&#x201C;SUSv3&#x201D;)</span> including
      <span class="St">ISO/IEC 9899:1999
      (&#x201C;ISO&#x00A0;C99&#x201D;)</span></td>
  </tr>
  <tr id="_XOPEN_SOURCE~4">
    <td><a class="permalink" href="#_XOPEN_SOURCE~4"><code class="Dv">_XOPEN_SOURCE
      = 700</code></a></td>
    <td><span class="St">IEEE Std 1003.1-2008 (&#x201C;POSIX.1&#x201D;)</span>
      and XPG extensions to <span class="St">Version&#x00A0;4 of the Single UNIX
      Specification (&#x201C;SUSv4&#x201D;)</span> including
      <span class="St">ISO/IEC 9899:1999
      (&#x201C;ISO&#x00A0;C99&#x201D;)</span></td>
  </tr>
  <tr id="_XOPEN_SOURCE~5">
    <td><a class="permalink" href="#_XOPEN_SOURCE~5"><code class="Dv">_XOPEN_SOURCE
      = 800</code></a></td>
    <td>and XPG extensions to Version 5 of the Single UNIX Specification
      (&#x201C;SUSv5&#x201D;) including ISO/IEC 9899:2018 (&#x201C;ISO
      C17&#x201D;)</td>
  </tr>
  <tr id="_ANSI_SOURCE">
    <td><a class="permalink" href="#_ANSI_SOURCE"><code class="Dv">_ANSI_SOURCE</code></a></td>
    <td><span class="St">ANSI X3.159-1989
      (&#x201C;ANSI&#x00A0;C89&#x201D;)</span></td>
  </tr>
  <tr id="_C99_SOURCE">
    <td><a class="permalink" href="#_C99_SOURCE"><code class="Dv">_C99_SOURCE</code></a></td>
    <td><span class="St">ISO/IEC 9899:1999
      (&#x201C;ISO&#x00A0;C99&#x201D;)</span></td>
  </tr>
  <tr id="_C11_SOURCE">
    <td><a class="permalink" href="#_C11_SOURCE"><code class="Dv">_C11_SOURCE</code></a></td>
    <td><span class="St">ISO/IEC 9899:2011
      (&#x201C;ISO&#x00A0;C11&#x201D;)</span></td>
  </tr>
  <tr id="_C23_SOURCE">
    <td><a class="permalink" href="#_C23_SOURCE"><code class="Dv">_C23_SOURCE</code></a></td>
    <td></td>
  </tr>
  <tr id="_BSD_SOURCE">
    <td><a class="permalink" href="#_BSD_SOURCE"><code class="Dv">_BSD_SOURCE</code></a></td>
    <td>Everything, including <span class="Ux">FreeBSD extensions</span></td>
  </tr>
</table>
<p class="Pp">Note: and XPG extensions to Version 5 of the Single UNIX
    Specification (&quot;SUSv5&quot;) support is incomplete.</p>
<p class="Pp">When both POSIX and C environments are selected, the POSIX
    environment selects which C environment is used. However, when C11 dialect
    is selected with <span class="St">IEEE Std 1003.1-2008
    (&#x201C;POSIX.1&#x201D;)</span>, definitions for <span class="St">ISO/IEC
    9899:2011 (&#x201C;ISO&#x00A0;C11&#x201D;)</span> are also included.
    Likewise, when C23 dialog is selected with <span class="St">IEEE Std
    1003.1-2008 (&#x201C;POSIX.1&#x201D;)</span> or, definitions for are also
    included.</p>
</section>
<section class="Ss">
<h2 class="Ss" id="Header_Visibility_Macros"><a class="permalink" href="#Header_Visibility_Macros">Header
  Visibility Macros</a></h2>
<p class="Pp">These macros are set by <code class="Nm">cdefs</code> to control
    the visibility of different standards. Users must not define these, and
    doing so will produced undefined results. They are documented here for
    developers working on system's header files.</p>
<table class="Bl-column">
  <tr id="__XSI_VISIBLE">
    <td><a class="permalink" href="#__XSI_VISIBLE"><code class="Dv">__XSI_VISIBLE</code></a></td>
    <td>Restricts the visibility of XOPEN Single Unix Standard version. Possible
      values are 500, 600, 700 or 800, corresponding to Issue 5, 6, 7, or 8 of
      the Single Unix Standard. These are extra functions in addition to the
      normal POSIX ones.</td>
  </tr>
  <tr id="__POSIX_VISIBLE">
    <td><a class="permalink" href="#__POSIX_VISIBLE"><code class="Dv">__POSIX_VISIBLE</code></a></td>
    <td>Make symbols associated with certain standards versions visible. Set to
      the value assigned to <code class="Dv">_POSIX_C_SOURCE</code> by
      convention with 199009 for <span class="St">IEEE Std 1003.1-1988
      (&#x201C;POSIX.1&#x201D;)</span> and 199209 <span class="St">IEEE Std
      1003.1-1990 (&#x201C;POSIX.1&#x201D;)</span>.</td>
  </tr>
  <tr id="__ISO_C_VISIBLE">
    <td><a class="permalink" href="#__ISO_C_VISIBLE"><code class="Dv">__ISO_C_VISIBLE</code></a></td>
    <td>The C level that's visible. Possible values include 1990, 1999, 2011,
      2017 and 2023 for <span class="St">ISO/IEC 9899:1990
      (&#x201C;ISO&#x00A0;C90&#x201D;)</span>, <span class="St">ISO/IEC
      9899:1999 (&#x201C;ISO&#x00A0;C99&#x201D;)</span>,
      <span class="St">ISO/IEC 9899:2011
      (&#x201C;ISO&#x00A0;C11&#x201D;)</span>, ISO/IEC 9899:2018 (&quot;ISO
      C17&quot;), and, respectively.</td>
  </tr>
  <tr id="__BSD_VISIBLE">
    <td><a class="permalink" href="#__BSD_VISIBLE"><code class="Dv">__BSD_VISIBLE</code></a></td>
    <td>1 if the <span class="Ux">FreeBSD</span> extensions are visible, 0
      otherwise.</td>
  </tr>
  <tr id="__EXT1_VISIBLE">
    <td><a class="permalink" href="#__EXT1_VISIBLE"><code class="Dv">__EXT1_VISIBLE</code></a></td>
    <td>1 if the <span class="St">ISO/IEC 9899:2011
      (&#x201C;ISO&#x00A0;C11&#x201D;)</span> Appendix K 3.7.4.1 extensions are
      visible, 0 otherwise.</td>
  </tr>
</table>
</section>
</section>
<section class="Sh">
<h1 class="Sh" id="Supported_C++_Environments"><a class="permalink" href="#Supported_C++_Environments">Supported
  C++ Environments</a></h1>
<p class="Pp"><span class="Ux">FreeBSD</span> supports C++11 and newer standards
    fully.</p>
<dl class="Bl-tag">
  <dt id="__cplusplus">ISO/IEC 14882:1998 (&quot;C++98&quot;)</dt>
  <dd><a class="permalink" href="#__cplusplus"><code class="Dv">__cplusplus =
      199711</code></a>
    <p class="Pp">The first standardized version of C++. Unlike K &amp; R
        support in C, compilers dropped support for versions of the language
        prior to C++98.</p>
  </dd>
  <dt id="__cplusplus~2">ISO/IEC 14882:2003 (&quot;C++03&quot;)</dt>
  <dd><a class="permalink" href="#__cplusplus~2"><code class="Dv">__cplusplus =
      199711</code></a>
    <p class="Pp">Note, this is the same value as C++98. C++03 did not define a
        new value for <code class="Dv">__cplusplus</code>. There is no way, at
        compile time, to detect the difference. The standard resolved a number
        of defect reports and slightly expanded value initialization. Most
        compilers support it the same as C++98.</p>
  </dd>
  <dt id="__cplusplus~3">ISO/IEC 14882:2011 (&quot;C++11&quot;)</dt>
  <dd><a class="permalink" href="#__cplusplus~3"><code class="Dv">__cplusplus =
      201103</code></a></dd>
  <dt id="__cplusplus~4">ISO/IEC 14882:2014 (&quot;C++14&quot;)</dt>
  <dd><a class="permalink" href="#__cplusplus~4"><code class="Dv">__cplusplus =
      201402</code></a></dd>
  <dt id="__cplusplus~5">ISO/IEC 14882:2017 (&quot;C++17&quot;)</dt>
  <dd><a class="permalink" href="#__cplusplus~5"><code class="Dv">__cplusplus =
      201703</code></a></dd>
  <dt id="__cplusplus~6">ISO/IEC 14882:2020 (&quot;C++20&quot;)</dt>
  <dd><a class="permalink" href="#__cplusplus~6"><code class="Dv">__cplusplus =
      202002</code></a></dd>
  <dt id="__cplusplus~7">ISO/IEC 14882:2023 (&quot;C++23&quot;)</dt>
  <dd><a class="permalink" href="#__cplusplus~7"><code class="Dv">__cplusplus =
      202302</code></a></dd>
</dl>
<p class="Pp"><span class="Ux">FreeBSD</span> uses llvm project's libc++.
    However, they are removing support for C++ prior to C++11. While programs
    can still build with earlier environments for now, these changes mean that
    <code class="Fl">-pedantic-errors</code> cannot be reliably enabled for
    standards older than C++11.</p>
</section>
<section class="Sh">
<h1 class="Sh" id="HISTORY"><a class="permalink" href="#HISTORY">HISTORY</a></h1>
<p class="Pp"><code class="In">&lt;<a class="In">sys/cdefs.h</a>&gt;</code>
    first appeared in <span class="Ux">4.3BSD-NET/2</span>.</p>
</section>
</div>
<table class="foot">
  <tr>
    <td class="foot-date">May 9, 2025</td>
    <td class="foot-os">FreeBSD 15.0</td>
  </tr>
</table>