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| author | Pedro Alves <palves@redhat.com> | 2016-10-13 00:27:45 +0100 |
|---|---|---|
| committer | Pedro Alves <palves@redhat.com> | 2016-10-28 16:03:19 +0100 |
| commit | 0bcda68539948828795564b35a497dc69c27f768 (patch) | |
| tree | ffba724695a70ecf58bd556ee6f39cf52af099f2 /gdb/acinclude.m4 | |
| parent | 87106a7b0a3c403832f15aa316d5d6d2434e323f (diff) | |
| download | binutils-gdb-0bcda68539948828795564b35a497dc69c27f768.tar.gz | |
gdb: Require C++11
Use AX_CXX_COMPILE_STDCXX to detect if the compiler supports C++11,
and if -std=xxx switches are necessary to enable C++11.
We need to tweak AX_CXX_COMPILE_STDCXX a bit though. Pristine
upstream AX_CXX_COMPILE_STDCXX appends -std=gnu++11 to CXX directly.
That doesn't work for us, because the top level Makefile passes CXX
down to subdirs, and that overrides whatever gdb/Makefile may set CXX
to. The result would be that a make invocation from the build/gdb/
directory would use "g++ -std=gnu++11" as expected, while a make
invocation at the top level would not.
So instead of having AX_CXX_COMPILE_STDCXX set CXX directly, tweak it
to AC_SUBST a separate variable -- CXX_DIALECT -- and use '$(CXX)
(CXX_DIALECT)' to compile/link.
Confirmed that this enables C++11 starting with gcc 4.8, the first gcc
release with full C++11 support.
Also confirmed that configure errors out gracefully with older GCC
releases:
checking whether /opt/gcc-4.7/bin/g++ supports C++11 features by default... no
checking whether /opt/gcc-4.7/bin/g++ supports C++11 features with -std=gnu++11... no
checking whether /opt/gcc-4.7/bin/g++ supports C++11 features with -std=gnu++0x... no
checking whether /opt/gcc-4.7/bin/g++ supports C++11 features with -std=c++11... no
checking whether /opt/gcc-4.7/bin/g++ supports C++11 features with -std=c++0x... no
checking whether /opt/gcc-4.7/bin/g++ supports C++11 features with +std=c++11... no
checking whether /opt/gcc-4.7/bin/g++ supports C++11 features with -h std=c++11... no
configure: error: *** A compiler with support for C++11 language features is required.
Makefile:9451: recipe for target 'configure-gdb' failed
make[1]: *** [configure-gdb] Error 1
make[1]: Leaving directory '/home/pedro/brno/pedro/gdb/mygit/cxx-convertion/build-gcc-4.7'
If we need to revert back to making C++11 optional, all that's
necessary is to change the "mandatory" to "optional" in configure.ac
and regenerate configure (both gdb and gdbserver).
gdb/ChangeLog:
2016-10-28 Pedro Alves <palves@redhat.com>
* Makefile.in (CXX_DIALECT): Get from configure.
(COMPILE.pre, CC_LD): Append $(CXX_DIALECT).
(FLAGS_TO_PASS): Pass CXX_DIALECT.
* acinclude.m4: Include ax_cxx_compile_stdcxx.m4.
* ax_cxx_compile_stdcxx.m4: Add FSF copyright header. Set and
AC_SUBST CXX_DIALECT instead of changing CXX/CXXCPP.
* configure.ac: Call AX_CXX_COMPILE_STDCXX.
* config.in: Regenerate.
* configure: Regenerate.
gdb/gdbserver/ChangeLog:
2016-10-28 Pedro Alves <palves@redhat.com>
* Makefile.in (CXX_DIALECT): Get from configure.
(COMPILE.pre, CC_LD): Append $(CXX_DIALECT).
* acinclude.m4: Include ../ax_cxx_compile_stdcxx.m4.
* configure.ac: Call AX_CXX_COMPILE_STDCXX.
* config.in: Regenerate.
* configure: Regenerate.
Diffstat (limited to 'gdb/acinclude.m4')
| -rw-r--r-- | gdb/acinclude.m4 | 2 |
1 files changed, 2 insertions, 0 deletions
diff --git a/gdb/acinclude.m4 b/gdb/acinclude.m4 index 4b3f7fcf95e..daf4a919de2 100644 --- a/gdb/acinclude.m4 +++ b/gdb/acinclude.m4 @@ -68,6 +68,8 @@ m4_include(libiberty.m4) dnl For GDB_AC_PTRACE. m4_include(ptrace.m4) +m4_include(ax_cxx_compile_stdcxx.m4) + ## ----------------------------------------- ## ## ANSIfy the C compiler whenever possible. ## ## From Franc,ois Pinard ## |