From 0bcda68539948828795564b35a497dc69c27f768 Mon Sep 17 00:00:00 2001 From: Pedro Alves Date: Thu, 13 Oct 2016 00:27:45 +0100 Subject: 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 * 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 * 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. --- gdb/config.in | 3 +++ 1 file changed, 3 insertions(+) (limited to 'gdb/config.in') diff --git a/gdb/config.in b/gdb/config.in index 3790d10..9c841ba 100644 --- a/gdb/config.in +++ b/gdb/config.in @@ -84,6 +84,9 @@ /* Define to 1 if you have the header file. */ #undef HAVE_CURSES_H +/* define if the compiler supports basic C++11 syntax */ +#undef HAVE_CXX11 + /* Define to 1 if you have the declaration of `ADDR_NO_RANDOMIZE', and to 0 if you don't. */ #undef HAVE_DECL_ADDR_NO_RANDOMIZE -- cgit v1.1