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Implement a long-standing request to support tuning the size of the emergency buffer for allocating exceptions after malloc fails, or to disable that buffer entirely. It's now possible to disable the dynamic allocation of the buffer and use a fixed-size static buffer, via --enable-libstdcxx-static-eh-pool. This is a built-time choice that is baked into libstdc++ and so affects all code linked against that build of libstdc++. The size of the pool can be set by --with-libstdcxx-eh-pool-obj-count=N which is measured in units of sizeof(void*) not bytes. A given exception type such as std::system_error depends on the target, so giving a size in bytes wouldn't be portable across 16/32/64-bit targets. When libstdc++ is configured to use a dynamic buffer, the size of that buffer can now be tuned at runtime by setting the GLIBCXX_TUNABLES environment variable (c.f. PR libstdc++/88264). The number of exceptions to reserve space for is controlled by the "glibcxx.eh_pool.obj_count" and "glibcxx.eh_pool.obj_size" tunables. The pool will be sized to be able to allocate obj_count exceptions of size obj_size*sizeof(void*) and obj_count "dependent" exceptions rethrown by std::rethrow_exception. With the ability to tune the buffer size, we can reduce the default pool size on 32-bit and 16-bit targets. Most users never need to throw 1kB exceptions in parallel from hundreds of threads after malloc is OOM. The users who do need that can use the tunables to select larger sizes. The old defaults can be chosen at runtime by setting GLIBCXX_TUNABLES to: 64-bit: glibcxx.eh_pool.obj_count=64:glibcxx.eh_pool.obj_size=112 32-bit: glibcxx.eh_pool.obj_count=32:glibcxx.eh_pool.obj_size=104 Or approximated by configuring with: 64-bit: --with-libstdcxx-eh-pool-obj-count=252 32-bit: --with-libstdcxx-eh-pool-obj-count=94 libstdc++-v3/ChangeLog: PR libstdc++/68606 * Makefile.in: Regenerate. * acinclude.m4 (GLIBCXX_EMERGENCY_EH_ALLOC): New macro. * configure: Regenerate. * configure.ac: Use GLIBCXX_EMERGENCY_EH_ALLOC. * crossconfig.m4: Check for secure_getenv. * doc/Makefile.in: Regenerate. * doc/xml/manual/configure.xml: Document new configure options. * doc/xml/manual/evolution.xml: Document addition of tunables. * doc/xml/manual/using_exceptions.xml: Document emergency buffer and tunables. * doc/html/*: Regenerate. * include/Makefile.in: Regenerate. * libsupc++/Makefile.am: Use EH_POOL_FLAGS. * libsupc++/Makefile.in: Regenerate. * libsupc++/eh_alloc.cc (EMERGENCY_OBJ_SIZE): Define in units of sizeof(void*) not including the ABI's exception header. (EMERGENCY_OBJ_COUNT): Define as target-independent calculation based on word size. (MAX_OBJ_COUNT): Define macro for upper limit on pool size. (pool) [_GLIBCXX_EH_POOL_STATIC]: Use fixed-size buffer. (pool::buffer_size_in_bytes): New static member function. (pool::pool): Parse GLIBCXX_TUNABLES environment variable to set pool size at runtime. (pool::in_pool): Use std::less<void*> for total order. (__freeres) [_GLIBCXX_EH_POOL_STATIC]: Do nothing. (__cxa_free_exception, __cxa_free_dependent_exception): Add [[unlikely]] attributes. * po/Makefile.in: Regenerate. * python/Makefile.in: Regenerate. * src/Makefile.in: Regenerate. * src/c++11/Makefile.in: Regenerate. * src/c++17/Makefile.in: Regenerate. * src/c++20/Makefile.in: Regenerate. * src/c++98/Makefile.in: Regenerate. * src/filesystem/Makefile.in: Regenerate. * src/libbacktrace/Makefile.in: Regenerate. * testsuite/Makefile.in: Regenerate.
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<?xml version="1.0" encoding="UTF-8" standalone="no"?>
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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>Chapter 3. Using</title><meta name="generator" content="DocBook XSL Stylesheets Vsnapshot" /><meta name="keywords" content="ISO C++, library" /><meta name="keywords" content="ISO C++, runtime, library" /><link rel="home" href="../index.html" title="The GNU C++ Library" /><link rel="up" href="intro.html" title="Part I. Introduction" /><link rel="prev" href="make.html" title="Make" /><link rel="next" href="using_headers.html" title="Headers" /></head><body><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">Chapter 3. Using</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="make.html">Prev</a> </td><th width="60%" align="center">Part I.
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Introduction
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</th><td width="20%" align="right"> <a accesskey="n" href="using_headers.html">Next</a></td></tr></table><hr /></div><div class="chapter"><div class="titlepage"><div><div><h2 class="title"><a id="manual.intro.using"></a>Chapter 3. Using</h2></div></div></div><div class="toc"><p><strong>Table of Contents</strong></p><dl class="toc"><dt><span class="section"><a href="using.html#manual.intro.using.flags">Command Options</a></span></dt><dt><span class="section"><a href="using_headers.html">Headers</a></span></dt><dd><dl><dt><span class="section"><a href="using_headers.html#manual.intro.using.headers.all">Header Files</a></span></dt><dt><span class="section"><a href="using_headers.html#manual.intro.using.headers.mixing">Mixing Headers</a></span></dt><dt><span class="section"><a href="using_headers.html#manual.intro.using.headers.cheaders">The C Headers and <code class="code">namespace std</code></a></span></dt><dt><span class="section"><a href="using_headers.html#manual.intro.using.headers.pre">Precompiled Headers</a></span></dt></dl></dd><dt><span class="section"><a href="using_macros.html">Macros</a></span></dt><dt><span class="section"><a href="using_dual_abi.html">Dual ABI</a></span></dt><dd><dl><dt><span class="section"><a href="using_dual_abi.html#manual.intro.using.abi.trouble">Troubleshooting</a></span></dt></dl></dd><dt><span class="section"><a href="using_namespaces.html">Namespaces</a></span></dt><dd><dl><dt><span class="section"><a href="using_namespaces.html#manual.intro.using.namespaces.all">Available Namespaces</a></span></dt><dt><span class="section"><a href="using_namespaces.html#manual.intro.using.namespaces.std">namespace std</a></span></dt><dt><span class="section"><a href="using_namespaces.html#manual.intro.using.namespaces.comp">Using Namespace Composition</a></span></dt></dl></dd><dt><span class="section"><a href="using_dynamic_or_shared.html">Linking</a></span></dt><dd><dl><dt><span class="section"><a href="using_dynamic_or_shared.html#manual.intro.using.linkage.freestanding">Almost Nothing</a></span></dt><dt><span class="section"><a href="using_dynamic_or_shared.html#manual.intro.using.linkage.dynamic">Finding Dynamic or Shared Libraries</a></span></dt><dt><span class="section"><a href="using_dynamic_or_shared.html#manual.intro.using.linkage.experimental">Experimental Library Extensions</a></span></dt></dl></dd><dt><span class="section"><a href="using_concurrency.html">Concurrency</a></span></dt><dd><dl><dt><span class="section"><a href="using_concurrency.html#manual.intro.using.concurrency.prereq">Prerequisites</a></span></dt><dt><span class="section"><a href="using_concurrency.html#manual.intro.using.concurrency.thread_safety">Thread Safety</a></span></dt><dt><span class="section"><a href="using_concurrency.html#manual.intro.using.concurrency.atomics">Atomics</a></span></dt><dt><span class="section"><a href="using_concurrency.html#manual.intro.using.concurrency.io">IO</a></span></dt><dd><dl><dt><span class="section"><a href="using_concurrency.html#concurrency.io.structure">Structure</a></span></dt><dt><span class="section"><a href="using_concurrency.html#concurrency.io.defaults">Defaults</a></span></dt><dt><span class="section"><a href="using_concurrency.html#concurrency.io.future">Future</a></span></dt><dt><span class="section"><a href="using_concurrency.html#concurrency.io.alt">Alternatives</a></span></dt></dl></dd><dt><span class="section"><a href="using_concurrency.html#manual.intro.using.concurrency.containers">Containers</a></span></dt></dl></dd><dt><span class="section"><a href="using_exceptions.html">Exceptions</a></span></dt><dd><dl><dt><span class="section"><a href="using_exceptions.html#intro.using.exception.safety">Exception Safety</a></span></dt><dt><span class="section"><a href="using_exceptions.html#intro.using.exception.propagating">Exception Neutrality</a></span></dt><dt><span class="section"><a href="using_exceptions.html#intro.using.exception.alloc">Memory allocation</a></span></dt><dt><span class="section"><a href="using_exceptions.html#intro.using.exception.no">Doing without</a></span></dt><dt><span class="section"><a href="using_exceptions.html#intro.using.exception.compat">Compatibility</a></span></dt><dd><dl><dt><span class="section"><a href="using_exceptions.html#using.exception.compat.c">With <code class="literal">C</code></a></span></dt><dt><span class="section"><a href="using_exceptions.html#using.exception.compat.posix">With <code class="literal">POSIX</code> thread cancellation</a></span></dt></dl></dd></dl></dd><dt><span class="section"><a href="debug.html">Debugging Support</a></span></dt><dd><dl><dt><span class="section"><a href="debug.html#debug.compiler">Using <span class="command"><strong>g++</strong></span></a></span></dt><dt><span class="section"><a href="debug.html#debug.req">Debug Versions of Library Binary Files</a></span></dt><dt><span class="section"><a href="debug.html#debug.memory">Memory Leak Hunting</a></span></dt><dd><dl><dt><span class="section"><a href="debug.html#debug.memory.mtalloc">Non-memory leaks in Pool and MT allocators</a></span></dt></dl></dd><dt><span class="section"><a href="debug.html#debug.races">Data Race Hunting</a></span></dt><dt><span class="section"><a href="debug.html#debug.gdb">Using <span class="command"><strong>gdb</strong></span></a></span></dt><dt><span class="section"><a href="debug.html#debug.exceptions">Tracking uncaught exceptions</a></span></dt><dt><span class="section"><a href="debug.html#debug.debug_mode">Debug Mode</a></span></dt><dt><span class="section"><a href="debug.html#debug.compile_time_checks">Compile Time Checking</a></span></dt></dl></dd></dl></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="manual.intro.using.flags"></a>Command Options</h2></div></div></div><p>
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The set of features available in the GNU C++ library is shaped by
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several <a class="link" href="http://gcc.gnu.org/onlinedocs/gcc-4.3.2/gcc/Invoking-GCC.html" target="_top">GCC
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Command Options</a>. Options that impact libstdc++ are
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enumerated and detailed in the table below.
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</p><p>
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The standard library conforms to the dialect of C++ specified by the
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<code class="option">-std</code> option passed to the compiler.
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By default, <span class="command"><strong>g++</strong></span> is equivalent to
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<span class="command"><strong>g++ -std=gnu++17</strong></span> since GCC 11, and
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<span class="command"><strong>g++ -std=gnu++14</strong></span> in GCC 6, 7, 8, 9, and 10, and
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<span class="command"><strong>g++ -std=gnu++98</strong></span> for older releases.
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</p><div class="table"><a id="table.cmd_options"></a><p class="title"><strong>Table 3.1. C++ Command Options</strong></p><div class="table-contents"><table class="table" summary="C++ Command Options" border="1"><colgroup><col align="left" class="c1" /><col align="left" class="c2" /></colgroup><thead><tr><th align="left">Option Flags</th><th align="left">Description</th></tr></thead><tbody><tr><td align="left"><code class="literal">-std=c++98</code> or <code class="literal">-std=c++03</code>
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</td><td align="left">Use the 1998 ISO C++ standard plus amendments.</td></tr><tr><td align="left"><code class="literal">-std=gnu++98</code> or <code class="literal">-std=gnu++03</code>
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</td><td align="left">As directly above, with GNU extensions.</td></tr><tr><td align="left"><code class="literal">-std=c++11</code></td><td align="left">Use the 2011 ISO C++ standard.</td></tr><tr><td align="left"><code class="literal">-std=gnu++11</code></td><td align="left">As directly above, with GNU extensions.</td></tr><tr><td align="left"><code class="literal">-std=c++14</code></td><td align="left">Use the 2014 ISO C++ standard.</td></tr><tr><td align="left"><code class="literal">-std=gnu++14</code></td><td align="left">As directly above, with GNU extensions.</td></tr><tr><td align="left">
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<code class="literal">-fno-exceptions</code>
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</td><td align="left">See <a class="link" href="using_exceptions.html#intro.using.exception.no" title="Doing without">exception-free dialect</a></td></tr><tr><td align="left">
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<code class="literal">-fno-rtti</code>
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</td><td align="left">As above, but RTTI-free dialect.</td></tr><tr><td align="left"><code class="literal">-pthread</code></td><td align="left">For ISO C++11
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<code class="filename"><thread></code>,
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<code class="filename"><future></code>,
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<code class="filename"><mutex></code>,
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or <code class="filename"><condition_variable></code>.
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</td></tr><tr><td align="left"><code class="literal">-latomic</code></td><td align="left">Linking to <code class="filename">libatomic</code>
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is required for some uses of ISO C++11
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<code class="filename"><atomic></code>.
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</td></tr><tr><td align="left"><code class="literal">-lstdc++fs</code></td><td align="left">Linking to <code class="filename">libstdc++fs</code>
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is required for use of the Filesystem library extensions in
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<code class="filename"><experimental/filesystem></code>.
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</td></tr><tr><td align="left"><code class="literal">-lstdc++_libbacktrace</code></td><td align="left">Until C++23 support is non-experimental, linking to
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<code class="filename">libstdc++_libbacktrace.a</code>
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is required for use of the C++23 type
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<code class="classname">std::stacktrace</code>
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and related types in
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<code class="filename"><stacktrace></code>.
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</td></tr><tr><td align="left"><code class="literal">-fopenmp</code></td><td align="left">For <a class="link" href="parallel_mode.html" title="Chapter 18. Parallel Mode">parallel</a> mode.</td></tr><tr><td align="left"><code class="literal">-ltbb</code></td><td align="left">Linking to tbb (Thread Building Blocks) is required for use of the
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Parallel Standard Algorithms and execution policies in
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<code class="filename"><execution></code>.
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</td></tr></tbody></table></div></div><br class="table-break" /></div></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="make.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="intro.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="using_headers.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">Make </td><td width="20%" align="center"><a accesskey="h" href="../index.html">Home</a></td><td width="40%" align="right" valign="top"> Headers</td></tr></table></div></body></html> |