mirror of https://code.videolan.org/videolan/vlc
switch C++ support to C++17
As contribs keep being updated with newer versions of the language, we need to support a more modern version of C++ going forward. Setting -std=c++17 should not break existing contribs that are built with C++11 or C++14. In fact we already support the mix of versions between 11 and 14 without problem. Modern C++ compilers are designed to take care of this [1]. When switching to a new C++ version there might however be some slight differences on how the code is interpreted. These differences [2] might trigger some build errors for removed parts. [1] https://stackoverflow.com/questions/46746878/is-it-safe-to-link-c17-c14-and-c11-objects [2] https://www.open-std.org/JTC1/SC22/WG21/docs/papers/2018/p0636r3.html
This commit is contained in:
Steve Lhomme
Thomas Guillem
parent
fc787fe385
commit
5dcc5ff839
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@ -73,7 +73,7 @@ AC_C_CONST
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AC_C_INLINE
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AC_C_RESTRICT
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AC_LANG_PUSH([C++])
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AX_CXX_COMPILE_STDCXX_14([noext], [mandatory])
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AX_CXX_COMPILE_STDCXX_17([noext], [mandatory])
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AX_CXX_TYPEOF
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AC_LANG_POP([C++])
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@ -14,7 +14,7 @@ EXTRA_DIST = \
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nls.m4 \
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po.m4 \
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progtest.m4 \
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stdcxx_14.m4 \
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ax_cxx_compile_stdcxx.m4 \
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ax_cxx_compile_stdcxx_17.m4 \
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vlc.m4 \
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$(NULL)
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File diff suppressed because it is too large
Load Diff
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@ -0,0 +1,35 @@
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# =============================================================================
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# https://www.gnu.org/software/autoconf-archive/ax_cxx_compile_stdcxx_17.html
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# =============================================================================
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#
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# SYNOPSIS
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#
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# AX_CXX_COMPILE_STDCXX_17([ext|noext], [mandatory|optional])
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#
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# DESCRIPTION
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#
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# Check for baseline language coverage in the compiler for the C++17
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# standard; if necessary, add switches to CXX and CXXCPP to enable
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# support.
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#
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# This macro is a convenience alias for calling the AX_CXX_COMPILE_STDCXX
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# macro with the version set to C++17. The two optional arguments are
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# forwarded literally as the second and third argument respectively.
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# Please see the documentation for the AX_CXX_COMPILE_STDCXX macro for
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# more information. If you want to use this macro, you also need to
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# download the ax_cxx_compile_stdcxx.m4 file.
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#
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# LICENSE
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#
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# Copyright (c) 2015 Moritz Klammler <moritz@klammler.eu>
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# Copyright (c) 2016 Krzesimir Nowak <qdlacz@gmail.com>
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#
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# Copying and distribution of this file, with or without modification, are
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# permitted in any medium without royalty provided the copyright notice
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# and this notice are preserved. This file is offered as-is, without any
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# warranty.
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#serial 2
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AX_REQUIRE_DEFINED([AX_CXX_COMPILE_STDCXX])
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AC_DEFUN([AX_CXX_COMPILE_STDCXX_17], [AX_CXX_COMPILE_STDCXX([17], [$1], [$2])])
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191
m4/stdcxx_14.m4
191
m4/stdcxx_14.m4
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@ -1,191 +0,0 @@
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# ============================================================================
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# Based on http://www.gnu.org/software/autoconf-archive/ax_cxx_compile_stdcxx_11.html
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# ============================================================================
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#
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# SYNOPSIS
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#
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# AX_CXX_COMPILE_STDCXX_14([ext|noext],[mandatory|optional])
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#
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# DESCRIPTION
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#
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# Check for baseline language coverage in the compiler for the C++14
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# standard; if necessary, add switches to CXXFLAGS to enable support.
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#
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# The first argument, if specified, indicates whether you insist on an
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# extended mode (e.g. -std=gnu++14) or a strict conformance mode (e.g.
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# -std=c++14). If neither is specified, you get whatever works, with
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# preference for an extended mode.
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#
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# The second argument, if specified 'mandatory' or if left unspecified,
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# indicates that baseline C++14 support is required and that the macro
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# should error out if no mode with that support is found. If specified
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# 'optional', then configuration proceeds regardless, after defining
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# HAVE_CXX14 if and only if a supporting mode is found.
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#
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# LICENSE
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#
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# Copyright (c) 2008 Benjamin Kosnik <bkoz@redhat.com>
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# Copyright (c) 2012 Zack Weinberg <zackw@panix.com>
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# Copyright (c) 2013 Roy Stogner <roystgnr@ices.utexas.edu>
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# Copyright (c) 2014 Alexey Sokolov <sokolov@google.com>
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# Copyright (c) 2014, 2015 Google Inc.
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# Copyright (c) 2015, 2019 VLC authors and VideoLAN
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#
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# Copying and distribution of this file, with or without modification, are
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# permitted in any medium without royalty provided the copyright notice
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# and this notice are preserved. This file is offered as-is, without any
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# warranty.
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#serial 7
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m4_define([_AX_CXX_COMPILE_STDCXX_14_testbody], [[
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template <typename T>
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struct check
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{
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static_assert(sizeof(int) <= sizeof(T), "not big enough");
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};
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struct Base {
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virtual void f() {}
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};
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struct Child : public Base {
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virtual void f() override {}
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};
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typedef check<check<bool>> right_angle_brackets;
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int a;
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decltype(a) b;
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typedef check<int> check_type;
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check_type c;
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check_type&& cr = static_cast<check_type&&>(c);
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auto d = a;
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auto l = [](){};
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// http://stackoverflow.com/questions/13728184/template-aliases-and-sfinae
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// Clang 3.1 fails with headers of libstd++ 4.8.3 when using std::function because of this
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namespace test_template_alias_sfinae {
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struct foo {};
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template<typename T>
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using member = typename T::member_type;
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template<typename T>
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void func(...) {}
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template<typename T>
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void func(member<T>*) {}
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void test() {
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func<foo>(0);
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}
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}
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#include <cinttypes>
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#include <climits>
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#include <cstddef>
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constexpr uint64_t constant_u64 = UINT64_C(0x100000000);
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constexpr unsigned constant_lim = UINT_MAX;
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const char *constant_fmt = "%" PRIu64, *constant_scn = "%" SCNu64;
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constexpr size_t constant_align = alignof (std::max_align_t);
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#include <memory>
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namespace lambda_init_capture
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{
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void foo()
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{
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std::unique_ptr<int> ptr(new int);
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auto lambda = [p = std::move(ptr)](){};
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lambda();
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}
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}
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#include <type_traits>
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namespace traits_helper_types
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{
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static_assert( std::is_same<char, std::remove_pointer_t<char*>>::value, "plonk" );
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}
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]])
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AC_DEFUN([AX_CXX_COMPILE_STDCXX_14], [dnl
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m4_if([$1], [], [],
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[$1], [ext], [],
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[$1], [noext], [],
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[m4_fatal([invalid argument `$1' to AX_CXX_COMPILE_STDCXX_14])])dnl
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m4_if([$2], [], [ax_cxx_compile_cxx14_required=true],
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[$2], [mandatory], [ax_cxx_compile_cxx14_required=true],
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[$2], [optional], [ax_cxx_compile_cxx14_required=false],
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[m4_fatal([invalid second argument `$2' to AX_CXX_COMPILE_STDCXX_14])])
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AC_LANG_PUSH([C++])dnl
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ac_success=no
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AC_CACHE_CHECK(whether $CXX supports C++14 features by default,
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ax_cv_cxx_compile_cxx14,
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[AC_COMPILE_IFELSE([AC_LANG_SOURCE([_AX_CXX_COMPILE_STDCXX_14_testbody])],
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[ax_cv_cxx_compile_cxx14=yes],
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[ax_cv_cxx_compile_cxx14=no])])
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if test x$ax_cv_cxx_compile_cxx14 = xyes; then
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ac_success=yes
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fi
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m4_if([$1], [noext], [], [dnl
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if test x$ac_success = xno; then
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for switch in -std=gnu++14 -std=gnu++1y; do
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cachevar=AS_TR_SH([ax_cv_cxx_compile_cxx14_$switch])
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AC_CACHE_CHECK(whether $CXX supports C++14 features with $switch,
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$cachevar,
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[ac_save_CXXFLAGS="$CXXFLAGS"
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CXXFLAGS="$CXXFLAGS $switch"
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AC_COMPILE_IFELSE([AC_LANG_SOURCE([_AX_CXX_COMPILE_STDCXX_14_testbody])],
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[eval $cachevar=yes],
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[eval $cachevar=no])
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CXXFLAGS="$ac_save_CXXFLAGS"])
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if eval test x\$$cachevar = xyes; then
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CXXFLAGS="$CXXFLAGS $switch"
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ac_success=yes
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break
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fi
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done
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fi])
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m4_if([$1], [ext], [], [dnl
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if test x$ac_success = xno; then
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for switch in -std=c++14 -std=c++1y; do
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cachevar=AS_TR_SH([ax_cv_cxx_compile_cxx14_$switch])
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AC_CACHE_CHECK(whether $CXX supports C++14 features with $switch,
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$cachevar,
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[ac_save_CXXFLAGS="$CXXFLAGS"
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CXXFLAGS="$CXXFLAGS $switch"
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AC_COMPILE_IFELSE([AC_LANG_SOURCE([_AX_CXX_COMPILE_STDCXX_14_testbody])],
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[eval $cachevar=yes],
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[eval $cachevar=no])
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CXXFLAGS="$ac_save_CXXFLAGS"])
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if eval test x\$$cachevar = xyes; then
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CXXFLAGS="$CXXFLAGS $switch"
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ac_success=yes
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break
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fi
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done
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fi])
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AC_LANG_POP([C++])
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if test x$ax_cxx_compile_cxx14_required = xtrue; then
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if test x$ac_success = xno; then
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AC_MSG_ERROR([*** A compiler with support for C++14 language features is required.])
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fi
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else
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if test x$ac_success = xno; then
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HAVE_CXX14=0
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AC_MSG_NOTICE([No compiler with C++14 support was found])
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else
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HAVE_CXX14=1
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AC_DEFINE(HAVE_CXX14,1,
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[define if the compiler supports basic C++14 syntax])
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fi
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AC_SUBST(HAVE_CXX14)
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fi
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])
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@ -1,6 +1,6 @@
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project('VLC', ['c', 'cpp'],
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version: '4.0.0-dev',
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default_options: ['c_std=gnu11', 'cpp_std=c++14'],
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default_options: ['c_std=gnu11', 'cpp_std=c++17'],
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meson_version: '>=0.60.0')
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vlc_copyright_years = '1996-2018'
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