[FFmpeg-devel] [PATCH 1/2] configure: make the C and C++ standard settable

[James Almer <jamrial@gmail.com>]

Fallback to C11, the minimum supported version, if the requested standard is
not supported by the compliler.
Also, enforce C11 on the host compiler, same as we already do for C11 on the
target compiler.

Signed-off-by: James Almer <jamrial@gmail.com>
---
 configure | 55 ++++++++++++++++++++++++++++++++++++++++++++++---------
 1 file changed, 46 insertions(+), 9 deletions(-)

diff --git a/configure b/configure
index e019d1b996..b10d081549 100755
--- a/configure
+++ b/configure
@@ -387,7 +387,9 @@ Toolchain options:
   --windres=WINDRES        use windows resource compiler WINDRES [$windres_default]
   --x86asmexe=EXE          use nasm-compatible assembler EXE [$x86asmexe_default]
   --cc=CC                  use C compiler CC [$cc_default]
+  --stdc=STDC              use C standard STDC [$stdc_default]
   --cxx=CXX                use C compiler CXX [$cxx_default]
+  --stdcxx=STDCXX          use C standard STDCXX [$stdcxx_default]
   --objcc=OCC              use ObjC compiler OCC [$cc_default]
   --dep-cc=DEPCC           use dependency generator DEPCC [$cc_default]
   --nvcc=NVCC              use Nvidia CUDA compiler NVCC or clang [$nvcc_default]
@@ -1454,6 +1456,21 @@ test_cflags_cc(){
 EOF
 }
 
+test_cxxflags_cc(){
+    log test_cxxflags_cc "$@"
+    flags=$1
+    header=$2
+    condition=$3
+    shift 3
+    set -- $($cflags_filter "$flags")
+    test_cxx "$@" <<EOF
+#include <$header>
+#if !($condition)
+#error "unsatisfied condition: $condition"
+#endif
+EOF
+}
+
 check_lib(){
     log check_lib "$@"
     name="$1"
@@ -1695,6 +1712,21 @@ int x;
 EOF
 }
 
+test_host_cflags_cc(){
+    log test_host_cflags_cc "$@"
+    flags=$1
+    header=$2
+    condition=$3
+    shift 3
+    set -- $($host_cflags_filter "$flags")
+    test_host_cc "$@" <<EOF
+#include <$header>
+#if !($condition)
+#error "unsatisfied condition: $condition"
+#endif
+EOF
+}
+
 test_host_cpp_condition(){
     log test_host_cpp_condition "$@"
     header=$1
@@ -3980,6 +4012,8 @@ mandir_default='${prefix}/share/man'
 # toolchain
 ar_default="ar"
 cc_default="gcc"
+stdc_default="c11"
+stdcxx_default="c++11"
 cxx_default="g++"
 host_cc_default="gcc"
 doxygen_default="doxygen"
@@ -4587,7 +4621,7 @@ if enabled cuda_nvcc; then
 fi
 
 set_default arch cc cxx doxygen pkg_config ranlib strip sysinclude \
-    target_exec x86asmexe metalcc metallib
+    target_exec x86asmexe metalcc metallib stdc stdcxx
 enabled cross_compile || host_cc_default=$cc
 set_default host_cc
 
@@ -4757,7 +4791,7 @@ icl_flags(){
             # Despite what Intel's documentation says -Wall, which is supported
             # on Windows, does enable remarks so disable them here.
             -Wall)                echo $flag -Qdiag-disable:remark ;;
-            -std=c11)             echo -Qstd=c11 ;;
+            -std=$stdc)           echo -Qstd=$stdc ;;
             -flto*)               echo -ipo ;;
         esac
     done
@@ -4805,7 +4839,7 @@ suncc_flags(){
                     athlon*)                   echo -xarch=pentium_proa  ;;
                 esac
                 ;;
-            -std=c11)             echo -xc11              ;;
+            -std=$stdc)           echo -x$stdc            ;;
             -fomit-frame-pointer) echo -xregs=frameptr    ;;
             -fPIC)                echo -KPIC -xcode=pic32 ;;
             -W*,*)                echo $flag              ;;
@@ -4894,8 +4928,8 @@ probe_cc(){
         _type=suncc
         _ident=$($_cc -V 2>&1 | head -n1 | cut -d' ' -f 2-)
         _DEPCMD='$(DEP$(1)) $(DEP$(1)FLAGS) $($(1)DEP_FLAGS) $< | sed -e "1s,^.*: ,$@: ," -e "\$$!s,\$$, \\\," -e "1!s,^.*: , ," > $(@:.o=.d)'
-        _DEPFLAGS='-xM1 -xc11'
-        _ldflags='-std=c11'
+        _DEPFLAGS='-xM1 -x$stdc'
+        _ldflags='-std=$stdc'
         _cflags_speed='-O5'
         _cflags_size='-O5 -xspace'
         _flags_filter=suncc_flags
@@ -5526,18 +5560,21 @@ fi
 
 add_cppflags -D_ISOC11_SOURCE
 add_cxxflags -D__STDC_CONSTANT_MACROS
-check_cxxflags -std=c++11 || check_cxxflags -std=c++0x
+test_cxxflags_cc -std=$stdcxx ctype.h "__cplusplus >= 201103L" &&
+    add_cxxflags -std=$stdcxx || { check_cxxflags -std=c++11 || check_cxxflags -std=c++0x; }
 
 # some compilers silently accept -std=c11, so we also need to check that the
 # version macro is defined properly
-test_cflags_cc -std=c11 ctype.h "__STDC_VERSION__ >= 201112L" &&
-    add_cflags -std=c11 || die "Compiler lacks C11 support"
+test_cflags_cc -std=$stdc ctype.h "__STDC_VERSION__ >= 201112L" &&
+    add_cflags -std=$stdc || die "Compiler lacks C11 support"
 
 check_cppflags -D_FILE_OFFSET_BITS=64
 check_cppflags -D_LARGEFILE_SOURCE
 
 add_host_cppflags -D_ISOC11_SOURCE
-check_host_cflags -std=c11
+test_host_cflags_cc -std=$stdc ctype.h "__STDC_VERSION__ >= 201112L" &&
+    add_host_cflags -std=$stdc || die "Host compiler lacks C11 support"
+
 check_host_cflags -Wall
 check_host_cflags $host_cflags_speed
 
-- 
2.44.0

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