build: force a c++ standard to be specified
Newer compilers may switch to newer standards by default. For example, gcc6 uses std=gnu++14 by default.
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5f0556d032
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9829c54de2
2 changed files with 8 additions and 2 deletions
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@ -57,8 +57,14 @@ AC_DEFUN([AX_CXX_COMPILE_STDCXX], [dnl
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[$3], [mandatory], [ax_cxx_compile_cxx$1_required=true],
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[$3], [optional], [ax_cxx_compile_cxx$1_required=false],
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[m4_fatal([invalid third argument `$3' to AX_CXX_COMPILE_STDCXX])])
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m4_if([$4], [], [ax_cxx_compile_cxx$1_try_default=true],
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[$4], [default], [ax_cxx_compile_cxx$1_try_default=true],
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[$4], [nodefault], [ax_cxx_compile_cxx$1_try_default=false],
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[m4_fatal([invalid fourth argument `$4' to AX_CXX_COMPILE_STDCXX])])
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AC_LANG_PUSH([C++])dnl
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ac_success=no
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m4_if([$4], [nodefault], [], [dnl
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AC_CACHE_CHECK(whether $CXX supports C++$1 features by default,
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ax_cv_cxx_compile_cxx$1,
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[AC_COMPILE_IFELSE([AC_LANG_SOURCE([_AX_CXX_COMPILE_STDCXX_testbody_$1])],
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@ -66,7 +72,7 @@ AC_DEFUN([AX_CXX_COMPILE_STDCXX], [dnl
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[ax_cv_cxx_compile_cxx$1=no])])
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if test x$ax_cv_cxx_compile_cxx$1 = xyes; then
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ac_success=yes
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fi
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fi])
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m4_if([$2], [noext], [], [dnl
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if test x$ac_success = xno; then
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@ -55,7 +55,7 @@ case $host in
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;;
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esac
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dnl Require C++11 compiler (no GNU extensions)
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AX_CXX_COMPILE_STDCXX([11], [noext], [mandatory])
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AX_CXX_COMPILE_STDCXX([11], [noext], [mandatory], [nodefault])
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dnl Check if -latomic is required for <std::atomic>
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CHECK_ATOMIC
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