omit -std=gnu23 for the upcoming gcc-15

git-svn-id: https://svn.r-project.org/R/trunk@88157 00db46b3-68df-0310-9c12-caf00c1e9a41

Author: ripley

config.site

@@ -44,6 +44,7 @@
 ## which runs the compiler, for example 'c99'.
 ## It is also necessary to set the architecture here, e.g. 'gcc -m32'.
 ## If this is a wrapper it should pass on --version to the real compiler.
+## This will be replaced by CC23 (see below) if a C23 compiler is found.
 ## CC=
 
 ## Debugging and optimization options for the C compiler.
@@ -69,11 +70,12 @@
 
 ## Ditto for a compiler that supports C23 features.
 ## For example 'CC23=clang-15 -std=gnu2x'
-## -std=gnu2x is supported by at least GCC >= 12, LLVM clang >= 15 and Apple clang >= 16 
-## Eventually -std=gnu23 will be supported and preferred
-## (and is by GCC >= 14 and LLVM >= 18).
-## Default to CC and CFLAGS with any -std options removed, then
-## -std=gmu2x appended to CC.
+## This is the default for GCC >= 15.
+## -std=gnu23 is addeds where supported
+## (it is by GCC >= 14, LLVM clang >= 18 and Apple Clang >= 17).
+## -std=gnu2x is supported by at least GCC 12-14, LLVM clang >= 15 and Apple clang >= 16 
+## Default to CC and CFLAGS with any -std options removed, then with
+## -std=gmu23 then -std=gmu2x appended to CC
 ## CC23=
 ## C23FLAGS=
 

configure

@@ -8116,7 +8116,8 @@ CC_save=${CC}
 CFLAGS_save=${CFLAGS}
 CC_SUB=`echo "${CC}" | sed 's/-std=[^ ]*//'`
 CFLAGS_SUB=`echo "${CFLAGS}" | sed -e 's/-std=[^ ]*//'`
-: ${CC23="${CC_SUB} -std=gnu23"}
+## try first without any additional -std
+: ${CC23="${CC_SUB}"}
 : ${C23FLAGS="${CFLAGS_SUB}"}
 CC=${CC23}
 CFLAGS=${C23FLAGS}
@@ -8169,6 +8170,63 @@ fi
 { printf "%s\n" "$as_me:${as_lineno-$LINENO}: result: $r_cv_C23" >&5
 printf "%s\n" "$r_cv_C23" >&6; }
 
+
+if test x${r_cv_C23} = xno; then
+CC23="${CC_SUB} -std=gnu23"
+C23FLAGS="${CFLAGS_SUB}"
+CC=${CC23}
+CFLAGS=${C23FLAGS}
+unset r_cv_C23
+{ printf "%s\n" "$as_me:${as_lineno-$LINENO}: checking whether ${CC} is a C23 compiler" >&5
+printf %s "checking whether ${CC} is a C23 compiler... " >&6; }
+if test ${r_cv_C23+y}
+then :
+  printf %s "(cached) " >&6
+else case e in #(
+  e) if test "$cross_compiling" = yes
+then :
+  r_cv_C23=no
+else case e in #(
+  e) cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+
+#ifdef __STDC_VERSION__
+# if __STDC_VERSION__ < 202000L
+#  error "Compiler does not claim C23 conformance"
+# endif
+#else
+# error "Compiler does not advertise ISO C conformance"
+#endif
+
+// Most new features have feature tests. but bool type is fundamental.
+
+int main(void) {
+     bool x = true;
+
+     return 0;
+}
+
+
+_ACEOF
+if ac_fn_c_try_run "$LINENO"
+then :
+  r_cv_C23=yes
+else case e in #(
+  e) r_cv_C23=no ;;
+esac
+fi
+rm -f core *.core core.conftest.* gmon.out bb.out conftest$ac_exeext \
+  conftest.$ac_objext conftest.beam conftest.$ac_ext ;;
+esac
+fi
+ ;;
+esac
+fi
+{ printf "%s\n" "$as_me:${as_lineno-$LINENO}: result: $r_cv_C23" >&5
+printf "%s\n" "$r_cv_C23" >&6; }
+
+fi
+
 if test x${r_cv_C23} = xno; then
 unset r_cv_C23
 CC23="${CC_SUB} -std=gnu2x"
@@ -8222,6 +8280,7 @@ fi
 printf "%s\n" "$r_cv_C23" >&6; }
 
 fi
+
 if test x${r_cv_C23} = xno; then
 CC23=
 C23FLAGS=
@@ -27550,7 +27609,7 @@ _ACEOF
 # flags.
 r_save_CFLAGS=$CFLAGS
 CFLAGS="$CFLAGS $r_verb"
-(eval echo $as_me:27553: \"$ac_link\") >&5
+(eval echo $as_me:27612: \"$ac_link\") >&5
 r_c_v_output=`eval $ac_link 5>&1 2>&1 | grep -v 'Driving:'`
 echo "$r_c_v_output" >&5
 CFLAGS=$r_save_CFLAGS
@@ -27628,7 +27687,7 @@ _ACEOF
 # flags.
 r_save_CFLAGS=$CFLAGS
 CFLAGS="$CFLAGS $r_cv_prog_c_v"
-(eval echo $as_me:27631: \"$ac_link\") >&5
+(eval echo $as_me:27690: \"$ac_link\") >&5
 r_c_v_output=`eval $ac_link 5>&1 2>&1 | grep -v 'Driving:'`
 echo "$r_c_v_output" >&5
 CFLAGS=$r_save_CFLAGS

configure.ac

@@ -761,19 +761,31 @@ CC_save=${CC}
 CFLAGS_save=${CFLAGS}
 CC_SUB=`echo "${CC}" | sed 's/-std=[[^ ]]*//'`
 CFLAGS_SUB=`echo "${CFLAGS}" | sed -e 's/-std=[[^ ]]*//'`
-dnl this is a hack until -std=gnu23 is widely accepted.
-: ${CC23="${CC_SUB} -std=gnu23"}
+## try first without any additional -std
+: ${CC23="${CC_SUB}"}
 : ${C23FLAGS="${CFLAGS_SUB}"}
 CC=${CC23}
 CFLAGS=${C23FLAGS}
 unset r_cv_C23
 R_C23
+
+if test x${r_cv_C23} = xno; then
+CC23="${CC_SUB} -std=gnu23"
+C23FLAGS="${CFLAGS_SUB}"
+CC=${CC23}
+CFLAGS=${C23FLAGS}
+unset r_cv_C23
+R_C23
+fi
+
+dnl this is a hack until -std=gnu23 is widely accepted.
 if test x${r_cv_C23} = xno; then
 unset r_cv_C23
 CC23="${CC_SUB} -std=gnu2x"
 CC=${CC23}
 R_C23
 fi
+
 if test x${r_cv_C23} = xno; then
 CC23=
 C23FLAGS=