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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 > Macros< / title > < meta name = "generator" content = "DocBook XSL-NS Stylesheets V1.78.1" / > < 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 = "using.html" title = "Chapter / > < link rel = "prev" href = "using_headers.html" title = "Headers" / > < link rel = "next" href = "using_dual_abi.html" title = "Dual ABI" / > < / head > < body > < div class = "navheader" > < table width = "100%" summary = "Navigation header" > < tr > < th colspan = "3" align = "center" > Macros< / th > < / tr > < tr > < td width = "20%" align = "left" > < a accesskey = "p" href = "using_headers.html" > Prev< / a > < / td > < th width = "60%" align = "center" > Chapter < / th > < td width = "20%" align = "right" > < a accesskey = "n" href = "using_dual_abi.html" > Next< / a > < / td > < / tr > < / table > < hr / > < / div > < div class = "section" > < div class = "titlepage" > < div > < div > < h2 class = "title" style = "clear: both" > < a id = "manual.intro.using.macros" > < / a > Macros< / h2 > < / div > < / div > < / div > < p >
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All library macros begin with < code class = "code" > _GLIBCXX_< / code > .
< / p > < p >
Furthermore, all pre-processor macros, switches, and
configuration options are gathered in the
file < code class = "filename" > c++config.h< / code > , which
is generated during the libstdc++ configuration and build
process. This file is then included when needed by files part of
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the public libstdc++ API, like
< code class = "filename" > < ios> < / code > . Most of these
macros should not be used by consumers of libstdc++, and are reserved
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for internal implementation use. < span class = "emphasis" > < em > These macros cannot
be redefined< / em > < / span > .
< / p > < p >
A select handful of macros control libstdc++ extensions and extra
features, or provide versioning information for the API. Only
those macros listed below are offered for consideration by the
general public.
< / p > < p > Below is the macro which users may check for library version
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information. < / p > < div class = "variablelist" > < dl class = "variablelist" > < dt > < span class = "term" > < code class = "code" > __GLIBCXX__< / code > < / span > < / dt > < dd > < p > The current version of
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libstdc++ in compressed ISO date format, as an unsigned
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long. For details on the value of this particular macro for a
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particular release, please consult the < a class = "link" href = "abi.html" title = "ABI Policy and Guidelines" >
ABI Policy and Guidelines< / a > appendix.
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< / p > < / dd > < / dl > < / div > < p > Below are the macros which users may change with #define/#undef or
with -D/-U compiler flags. The default state of the symbol is
listed.< / p > < p > < span class = "quote" > “< span class = "quote" > Configurable< / span > ”< / span > (or < span class = "quote" > “< span class = "quote" > Not configurable< / span > ”< / span > ) means
that the symbol is initially chosen (or not) based on
--enable/--disable options at library build and configure time
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(documented in
< a class = "link" href = "configure.html" title = "Configure" > Configure< / a > ),
with the various --enable/--disable choices being translated to
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#define/#undef).
< / p > < p > < acronym class = "acronym" > ABI< / acronym > means that changing from the default value may
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mean changing the < acronym class = "acronym" > ABI< / acronym > of compiled code. In other words,
these choices control code which has already been compiled (i.e., in a
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binary such as libstdc++.a/.so). If you explicitly #define or
#undef these macros, the < span class = "emphasis" > < em > headers< / em > < / span > may see different code
paths, but the < span class = "emphasis" > < em > libraries< / em > < / span > which you link against will not.
Experimenting with different values with the expectation of
consistent linkage requires changing the config headers before
building/installing the library.
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< / p > < div class = "variablelist" > < dl class = "variablelist" > < dt > < span class = "term" > < code class = "code" > _GLIBCXX_USE_DEPRECATED< / code > < / span > < / dt > < dd > < p >
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Defined by default. Not configurable. ABI-changing. Turning this off
removes older ARM-style iostreams code, and other anachronisms
from the API. This macro is dependent on the version of the
standard being tracked, and as a result may give different results for
< code class = "code" > -std=c++98< / code > and < code class = "code" > -std=c++11< / code > . This may
be useful in updating old C++ code which no longer meet the
requirements of the language, or for checking current code
against new language standards.
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< / p > < / dd > < dt > < span class = "term" > < code class = "code" > _GLIBCXX_USE_CXX11_ABI< / code > < / span > < / dt > < dd > < p >
Defined to the value < code class = "literal" > 1< / code > by default.
Configurable via < code class = "code" > --disable-libstdcxx-dual-abi< / code >
and/or < code class = "code" > --with-default-libstdcxx-abi< / code > .
ABI-changing.
When defined to a non-zero value the library headers will use the
new C++11-conforming ABI introduced in GCC 5, rather than the older
ABI introduced in GCC 3.4. This changes the definition of several
class templates, including < code class = "classname" > std:string< / code > ,
< code class = "classname" > std::list< / code > and some locale facets.
For more details see < a class = "xref" href = "using_dual_abi.html" title = "Dual ABI" > Dual ABI< / a > .
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< / p > < / dd > < dt > < span class = "term" > < code class = "code" > _GLIBCXX_CONCEPT_CHECKS< / code > < / span > < / dt > < dd > < p >
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Undefined by default. Configurable via
< code class = "code" > --enable-concept-checks< / code > . When defined, performs
compile-time checking on certain template instantiations to
detect violations of the requirements of the standard. This
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macro has no effect for freestanding implementations.
This is described in more detail in
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< a class = "link" href = "ext_compile_checks.html" title = "Chapter > Compile Time Checks< / a > .
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< / p > < / dd > < dt > < span class = "term" > < code class = "code" > _GLIBCXX_ASSERTIONS< / code > < / span > < / dt > < dd > < p >
Undefined by default. When defined, enables extra error checking in
the form of precondition assertions, such as bounds checking in
strings and null pointer checks when dereferencing smart pointers.
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< / p > < / dd > < dt > < span class = "term" > < code class = "code" > _GLIBCXX_DEBUG< / code > < / span > < / dt > < dd > < p >
Undefined by default. When defined, compiles user code using
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the < a class = "link" href = "debug_mode.html" title = "Chapter > debug mode< / a > .
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When defined, < code class = "code" > _GLIBCXX_ASSERTIONS< / code > is defined
automatically, so all the assertions enabled by that macro are also
enabled in debug mode.
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< / p > < / dd > < dt > < span class = "term" > < code class = "code" > _GLIBCXX_DEBUG_PEDANTIC< / code > < / span > < / dt > < dd > < p >
Undefined by default. When defined while compiling with
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the < a class = "link" href = "debug_mode.html" title = "Chapter > debug mode< / a > , makes
the debug mode extremely picky by making the use of libstdc++
extensions and libstdc++-specific behavior into errors.
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< / p > < / dd > < dt > < span class = "term" > < code class = "code" > _GLIBCXX_PARALLEL< / code > < / span > < / dt > < dd > < p > Undefined by default. When defined, compiles user code
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using the < a class = "link" href = "parallel_mode.html" title = "Chapter > parallel
mode< / a > .
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< / p > < / dd > < dt > < span class = "term" > < code class = "code" > _GLIBCXX_PROFILE< / code > < / span > < / dt > < dd > < p > Undefined by default. When defined, compiles user code
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using the < a class = "link" href = "profile_mode.html" title = "Chapter > profile
mode< / a > .
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< / p > < / dd > < dt > < span class = "term" > < code class = "code" > __STDCPP_WANT_MATH_SPEC_FUNCS__< / code > < / span > < / dt > < dd > < p > Undefined by default. When defined to a non-zero integer constant,
enables support for ISO/IEC 29124 Special Math Functions.
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