This patch corrects the manual w.r.t the default -std mode for C++,
which changed from -std=gnu++98 to -std=gnu++14 in GCC 6. (I was
slightly surprised to find that -ansi didn't change to mean -std=c++14
at the same time, but now I think that makes sense.)
I added a cross-reference from the C++ options section to the C
options section, so people looking for documentation of -std for C++
know where to look.
I also documented C++14 and the Concepts TS in standards.texi and
removed the description of C++11 as experimental (I left C++14
described as experimental, as that's still what it says at
https://gcc.gnu.org/projects/cxx1y.html).
Rather then repeating the "to obtain all the diagnostics required by
the standard" text about -pedantic/-pedantic-errors I left it only on
the first paragraph and then added a new paragraph about it later. I
also clarified that the extensions enabled by -std=gnu++XX are
different to the ones enabled without -pedantic, taking the wording
from the previous @section about C Standards.
OK for trunk?
commit a9e3d7d32a2cf7a0d651759d94fef2cb7e5cbd59
Author: Jonathan Wakely <jwak...@redhat.com>
Date: Wed Jan 13 11:38:52 2016 +0000
Improve documentation of -std option for C++
* doc/invoke.texi (C Dialect Options): Adjust -std default for C++.
(C++ Dialect Options): Add cross-reference to -std option.
* doc/standards.texi (C++ Language): Document C++14 support.
diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
index d77346d..93d501b 100644
--- a/gcc/doc/invoke.texi
+++ b/gcc/doc/invoke.texi
@@ -1780,8 +1780,7 @@ additional defect reports. Same as @option{-ansi} for C++ code.
@item gnu++98
@itemx gnu++03
-GNU dialect of @option{-std=c++98}. This is the default for
-C++ code.
+GNU dialect of @option{-std=c++98}.
@item c++11
@itemx c++0x
@@ -1801,6 +1800,7 @@ The name @samp{c++1y} is deprecated.
@item gnu++14
@itemx gnu++1y
GNU dialect of @option{-std=c++14}.
+This is the default for C++ code.
The name @samp{gnu++1y} is deprecated.
@item c++1z
@@ -2128,6 +2128,9 @@ In this example, only @option{-fstrict-enums} is an option meant
only for C++ programs; you can use the other options with any
language supported by GCC@.
+@xref{C Dialect Options,,Options Controlling C Dialect} for the description
+of @option{-std} and other options which are also relevant for C++ programs.
+
Here is a list of options that are @emph{only} for compiling C++ programs:
@table @gcctabopt
@@ -2313,7 +2316,8 @@ otherwise be invalid, or have different behavior.
@opindex fno-gnu-keywords
Do not recognize @code{typeof} as a keyword, so that code can use this
word as an identifier. You can use the keyword @code{__typeof__} instead.
-@option{-ansi} implies @option{-fno-gnu-keywords}.
+This option is implied by the strict ISO C++ dialects: @option{-ansi},
+@option{-std=c++98}, @option{-std=c++11}, etc.
@item -fno-implicit-templates
@opindex fno-implicit-templates
diff --git a/gcc/doc/standards.texi b/gcc/doc/standards.texi
index 55d57d4..c5f0573 100644
--- a/gcc/doc/standards.texi
+++ b/gcc/doc/standards.texi
@@ -171,8 +171,8 @@ information concerning the history of C that is available online, see
@section C++ Language
-GCC supports the original ISO C++ standard (1998) and contains
-experimental support for the second ISO C++ standard (2011).
+GCC supports the original ISO C++ standard published in 1998,
+and the 2011 and 2014 revisions.
The original ISO C++ standard was published as the ISO standard (ISO/IEC
14882:1998) and amended by a Technical Corrigenda published in 2003
@@ -188,25 +188,48 @@ warnings).
A revised ISO C++ standard was published in 2011 as ISO/IEC
14882:2011, and is referred to as C++11; before its publication it was
commonly referred to as C++0x. C++11 contains several
-changes to the C++ language, most of which have been implemented in an
-experimental C++11 mode in GCC@. For information
-regarding the C++11 features available in the experimental C++11 mode,
-see @uref{http://gcc.gnu.org/projects/@/cxx0x.html}. To select this
-standard in GCC, use the option @option{-std=c++11}; to obtain all the
-diagnostics required by the standard, you should also specify
-@option{-pedantic} (or @option{-pedantic-errors} if you want them to
-be errors rather than warnings).
+changes to the C++ language, all of which have been implemented in GCC@.
+For information regarding the C++11 features available in C++11 mode,
+see @uref{https://gcc.gnu.org/projects/@/cxx0x.html}. To select this
+standard in GCC, use the option @option{-std=c++11}.
+
+Another revised ISO C++ standard was published in 2014 as ISO/IEC
+14882:2014, and is referred to as C++14; before its publication it was
+sometimes referred to as C++1y. C++14 contains several further
+changes to the C++ language, all of which have been implemented in GCC@.
+For information
+regarding the C++14 features available in the experimental C++14 mode,
+see @uref{https://gcc.gnu.org/projects/@/cxx1y.html}. To select this
+standard in GCC, use the option @option{-std=c++14}.
+
+GCC also supports the C++ Concepts Technical Specification,
+ISO/IEC TS 19217:2015, which allows constraints to be defined for templates,
+allowing template arguments to be checked and for templates to be
+overloaded or specialized based on the constraints. Support for C++ Concepts
+is included in an experimental C++1z mode that corresponds to the next
+revision of the ISO C++ standard, expected to be published in 2017. To enable
+C++1z support in GCC, use the option @option{-std=c++17} or
+@option{-std=c++1z}.
More information about the C++ standards is available on the ISO C++
committee's web site at @uref{http://www.open-std.org/@/jtc1/@/sc22/@/wg21/}.
-By default, GCC provides some extensions to the C++ language; @xref{C++
+To obtain all the diagnostics required by any of the standard versions
+described above you should specify @option{-pedantic}
+or @option{-pedantic-errors}, otherwise GCC will allow some non-ISO C++
+features as extensions. @xref{Warning Options}.
+
+By default, GCC also provides some additional extensions to the C++ language
+that on rare occasions conflict with the C++ standard. @xref{C++
Dialect Options,Options Controlling C++ Dialect}. Use of the
-@option{-std} option listed above will disable these extensions. You
-may also select an extended version of the C++ language explicitly with
-@option{-std=gnu++98} (for C++98 with GNU extensions) or
-@option{-std=gnu++11} (for C++11 with GNU extensions). The default, if
-no C++ language dialect options are given, is @option{-std=gnu++98}.
+@option{-std} options listed above will disable these extensions where they
+they conflict with the C++ standard version selected. You may also
+select an extended version of the C++ language explicitly with
+@option{-std=gnu++98} (for C++98 with GNU extensions), or
+@option{-std=gnu++11} (for C++11 with GNU extensions), or
+@option{-std=gnu++14} (for C++14 with GNU extensions), or
+@option{-std=gnu++1z} (for C++1z with GNU extensions). The default, if
+no C++ language dialect options are given, is @option{-std=gnu++14}.
@section Objective-C and Objective-C++ Languages
@cindex Objective-C
