[CF 5934] v1 - Raise C requirement to C11

This branch was automatically generated by a robot using patches from an
email thread registered at:

https://commitfest.postgresql.org/patch/5934

The branch will be overwritten each time a new patch version is posted to
the thread, and also periodically to check for bitrot caused by changes
on the master branch.

Patch(es): https://www.postgresql.org/message-id/[email protected]
Author(s): Peter Eisentraut

Author: Commitfest Bot

configure

@@ -4475,190 +4475,49 @@ ac_compile='$CC -c $CFLAGS $CPPFLAGS conftest.$ac_ext >&5'
 ac_link='$CC -o conftest$ac_exeext $CFLAGS $CPPFLAGS $LDFLAGS conftest.$ac_ext $LIBS >&5'
 ac_compiler_gnu=$ac_cv_c_compiler_gnu
 
-   { $as_echo "$as_me:${as_lineno-$LINENO}: checking for $CC option to accept ISO C99" >&5
-$as_echo_n "checking for $CC option to accept ISO C99... " >&6; }
-if ${ac_cv_prog_cc_c99+:} false; then :
+
+# Detect option needed for C11
+# loosely modeled after code in later Autoconf versions
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for $CC option to accept ISO C11" >&5
+$as_echo_n "checking for $CC option to accept ISO C11... " >&6; }
+
+if ${pgac_cv_prog_cc_c11+:} false; then :
   $as_echo_n "(cached) " >&6
 else
-  ac_cv_prog_cc_c99=no
-ac_save_CC=$CC
-cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+  pgac_cv_prog_cc_c11=no
+pgac_save_CC=$CC
+for pgac_arg in '' '-std=gnu11' '-std=c11'; do
+  CC="$pgac_save_CC $pgac_arg"
+  cat confdefs.h - <<_ACEOF >conftest.$ac_ext
 /* end confdefs.h.  */
-#include <stdarg.h>
-#include <stdbool.h>
-#include <stdlib.h>
-#include <wchar.h>
-#include <stdio.h>
-
-// Check varargs macros.  These examples are taken from C99 6.10.3.5.
-#define debug(...) fprintf (stderr, __VA_ARGS__)
-#define showlist(...) puts (#__VA_ARGS__)
-#define report(test,...) ((test) ? puts (#test) : printf (__VA_ARGS__))
-static void
-test_varargs_macros (void)
-{
-  int x = 1234;
-  int y = 5678;
-  debug ("Flag");
-  debug ("X = %d\n", x);
-  showlist (The first, second, and third items.);
-  report (x>y, "x is %d but y is %d", x, y);
-}
-
-// Check long long types.
-#define BIG64 18446744073709551615ull
-#define BIG32 4294967295ul
-#define BIG_OK (BIG64 / BIG32 == 4294967297ull && BIG64 % BIG32 == 0)
-#if !BIG_OK
-  your preprocessor is broken;
-#endif
-#if BIG_OK
-#else
-  your preprocessor is broken;
+#if !defined __STDC_VERSION__ || __STDC_VERSION__ < 201112L
+# error "Compiler does not advertise C11 conformance"
 #endif
-static long long int bignum = -9223372036854775807LL;
-static unsigned long long int ubignum = BIG64;
-
-struct incomplete_array
-{
-  int datasize;
-  double data[];
-};
-
-struct named_init {
-  int number;
-  const wchar_t *name;
-  double average;
-};
-
-typedef const char *ccp;
-
-static inline int
-test_restrict (ccp restrict text)
-{
-  // See if C++-style comments work.
-  // Iterate through items via the restricted pointer.
-  // Also check for declarations in for loops.
-  for (unsigned int i = 0; *(text+i) != '\0'; ++i)
-    continue;
-  return 0;
-}
-
-// Check varargs and va_copy.
-static void
-test_varargs (const char *format, ...)
-{
-  va_list args;
-  va_start (args, format);
-  va_list args_copy;
-  va_copy (args_copy, args);
-
-  const char *str;
-  int number;
-  float fnumber;
-
-  while (*format)
-    {
-      switch (*format++)
-	{
-	case 's': // string
-	  str = va_arg (args_copy, const char *);
-	  break;
-	case 'd': // int
-	  number = va_arg (args_copy, int);
-	  break;
-	case 'f': // float
-	  fnumber = va_arg (args_copy, double);
-	  break;
-	default:
-	  break;
-	}
-    }
-  va_end (args_copy);
-  va_end (args);
-}
-
-int
-main ()
-{
-
-  // Check bool.
-  _Bool success = false;
-
-  // Check restrict.
-  if (test_restrict ("String literal") == 0)
-    success = true;
-  char *restrict newvar = "Another string";
-
-  // Check varargs.
-  test_varargs ("s, d' f .", "string", 65, 34.234);
-  test_varargs_macros ();
-
-  // Check flexible array members.
-  struct incomplete_array *ia =
-    malloc (sizeof (struct incomplete_array) + (sizeof (double) * 10));
-  ia->datasize = 10;
-  for (int i = 0; i < ia->datasize; ++i)
-    ia->data[i] = i * 1.234;
-
-  // Check named initializers.
-  struct named_init ni = {
-    .number = 34,
-    .name = L"Test wide string",
-    .average = 543.34343,
-  };
-
-  ni.number = 58;
-
-  int dynamic_array[ni.number];
-  dynamic_array[ni.number - 1] = 543;
-
-  // work around unused variable warnings
-  return (!success || bignum == 0LL || ubignum == 0uLL || newvar[0] == 'x'
-	  || dynamic_array[ni.number - 1] != 543);
-
-  ;
-  return 0;
-}
 _ACEOF
-for ac_arg in '' -std=gnu99 -std=c99 -c99 -AC99 -D_STDC_C99= -qlanglvl=extc99
-do
-  CC="$ac_save_CC $ac_arg"
-  if ac_fn_c_try_compile "$LINENO"; then :
-  ac_cv_prog_cc_c99=$ac_arg
+if ac_fn_c_try_compile "$LINENO"; then :
+  pgac_cv_prog_cc_c11=$pgac_arg
 fi
-rm -f core conftest.err conftest.$ac_objext
-  test "x$ac_cv_prog_cc_c99" != "xno" && break
+rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
+  test x"$pgac_cv_prog_cc_c11" != x"no" && break
 done
-rm -f conftest.$ac_ext
-CC=$ac_save_CC
-
-fi
-# AC_CACHE_VAL
-case "x$ac_cv_prog_cc_c99" in
-  x)
-    { $as_echo "$as_me:${as_lineno-$LINENO}: result: none needed" >&5
-$as_echo "none needed" >&6; } ;;
-  xno)
-    { $as_echo "$as_me:${as_lineno-$LINENO}: result: unsupported" >&5
-$as_echo "unsupported" >&6; } ;;
-  *)
-    CC="$CC $ac_cv_prog_cc_c99"
-    { $as_echo "$as_me:${as_lineno-$LINENO}: result: $ac_cv_prog_cc_c99" >&5
-$as_echo "$ac_cv_prog_cc_c99" >&6; } ;;
-esac
-if test "x$ac_cv_prog_cc_c99" != xno; then :
-
+CC=$pgac_save_CC
 fi
 
 
-
-# Error out if the compiler does not support C99, as the codebase
-# relies on that.
-if test "$ac_cv_prog_cc_c99" = no; then
-    as_fn_error $? "C compiler \"$CC\" does not support C99" "$LINENO" 5
+if test x"$pgac_cv_prog_cc_c11" = x"no"; then
+  { $as_echo "$as_me:${as_lineno-$LINENO}: result: unsupported" >&5
+$as_echo "unsupported" >&6; }
+  as_fn_error $? "C compiler \"$CC\" does not support C11" "$LINENO" 5
+elif test x"$pgac_cv_prog_cc_c11" = x""; then
+  { $as_echo "$as_me:${as_lineno-$LINENO}: result: none needed" >&5
+$as_echo "none needed" >&6; }
+else
+  { $as_echo "$as_me:${as_lineno-$LINENO}: result: $pgac_cv_prog_cc_c11" >&5
+$as_echo "$pgac_cv_prog_cc_c11" >&6; }
+  CC="$CC $pgac_cv_prog_cc_c11"
 fi
 
+
 ac_ext=cpp
 ac_cpp='$CXXCPP $CPPFLAGS'
 ac_compile='$CXX -c $CXXFLAGS $CPPFLAGS conftest.$ac_ext >&5'
@@ -4920,7 +4779,6 @@ ac_compiler_gnu=$ac_cv_c_compiler_gnu
 # Check if it's Intel's compiler, which (usually) pretends to be gcc,
 # but has idiosyncrasies of its own.  We assume icc will define
 # __INTEL_COMPILER regardless of CFLAGS.
-
 cat confdefs.h - <<_ACEOF >conftest.$ac_ext
 /* end confdefs.h.  */
 

configure.ac

@@ -364,14 +364,33 @@ pgac_cc_list="gcc cc"
 pgac_cxx_list="g++ c++"
 
 AC_PROG_CC([$pgac_cc_list])
-AC_PROG_CC_C99()
 
-# Error out if the compiler does not support C99, as the codebase
-# relies on that.
-if test "$ac_cv_prog_cc_c99" = no; then
-    AC_MSG_ERROR([C compiler "$CC" does not support C99])
+# Detect option needed for C11
+# loosely modeled after code in later Autoconf versions
+AC_MSG_CHECKING([for $CC option to accept ISO C11])
+AC_CACHE_VAL([pgac_cv_prog_cc_c11],
+[pgac_cv_prog_cc_c11=no
+pgac_save_CC=$CC
+for pgac_arg in '' '-std=gnu11' '-std=c11'; do
+  CC="$pgac_save_CC $pgac_arg"
+  AC_COMPILE_IFELSE([AC_LANG_SOURCE([[#if !defined __STDC_VERSION__ || __STDC_VERSION__ < 201112L
+# error "Compiler does not advertise C11 conformance"
+#endif]])], [[pgac_cv_prog_cc_c11=$pgac_arg]])
+  test x"$pgac_cv_prog_cc_c11" != x"no" && break
+done
+CC=$pgac_save_CC])
+
+if test x"$pgac_cv_prog_cc_c11" = x"no"; then
+  AC_MSG_RESULT([unsupported])
+  AC_MSG_ERROR([C compiler "$CC" does not support C11])
+elif test x"$pgac_cv_prog_cc_c11" = x""; then
+  AC_MSG_RESULT([none needed])
+else
+  AC_MSG_RESULT([$pgac_cv_prog_cc_c11])
+  CC="$CC $pgac_cv_prog_cc_c11"
 fi
 
+
 AC_PROG_CXX([$pgac_cxx_list])
 
 # Check if it's Intel's compiler, which (usually) pretends to be gcc,

doc/src/sgml/installation.sgml

@@ -71,10 +71,9 @@
 
     <listitem>
      <para>
-      You need an <acronym>ISO</acronym>/<acronym>ANSI</acronym> C compiler (at least
-      C99-compliant). Recent
-      versions of <productname>GCC</productname> are recommended, but
-      <productname>PostgreSQL</productname> is known to build using a wide variety
+      You need a C compiler that supports at least C11.  Recent versions of
+      <productname>GCC</productname> are recommended, but
+      <productname>PostgreSQL</productname> is known to build using a variety
       of compilers from different vendors.
      </para>
     </listitem>

doc/src/sgml/sources.sgml

@@ -907,12 +907,12 @@ BETTER: unrecognized node type: 42
     <title>C Standard</title>
     <para>
      Code in <productname>PostgreSQL</productname> should only rely on language
-     features available in the C99 standard. That means a conforming
-     C99 compiler has to be able to compile postgres, at least aside
+     features available in the C11 standard. That means a conforming
+     C11 compiler has to be able to compile postgres, at least aside
      from a few platform dependent pieces.
     </para>
     <para>
-     A few features included in the C99 standard are, at this time, not
+     A few features included in the C11 standard are, at this time, not
      permitted to be used in core <productname>PostgreSQL</productname>
      code. This currently includes variable length arrays, intermingled
      declarations and code, <literal>//</literal> comments, universal
@@ -924,13 +924,11 @@ BETTER: unrecognized node type: 42
      features can be used, if a fallback is provided.
     </para>
     <para>
-     For example <literal>_Static_assert()</literal> and
+     For example <literal>typeof()</literal> and
      <literal>__builtin_constant_p</literal> are currently used, even though
      they are from newer revisions of the C standard and a
      <productname>GCC</productname> extension respectively. If not available
-     we respectively fall back to using a C99 compatible replacement that
-     performs the same checks, but emits rather cryptic messages and do not
-     use <literal>__builtin_constant_p</literal>.
+     we do not use them.
     </para>
    </simplesect>
 

meson.build

@@ -280,10 +280,6 @@ elif host_system == 'windows'
     # define before including <time.h> for getting localtime_r() etc. on MinGW
     cppflags += '-D_POSIX_C_SOURCE'
   endif
-  if cc.get_id() == 'msvc'
-    # required for VA_ARGS_NARGS() in c.h; requires VS 2019
-    cppflags += '/Zc:preprocessor'
-  endif
 
   export_file_format = 'win'
   export_file_suffix = 'def'
@@ -550,44 +546,29 @@ dir_doc_extension = dir_doc / 'extension'
 # used, they need to be added to test_c_args as well.
 ###############################################################
 
-# Do we need -std=c99 to compile C99 code? We don't want to add -std=c99
-# unnecessarily, because we optionally rely on newer features.
-c99_test = '''
-#include <stdbool.h>
-#include <complex.h>
-#include <tgmath.h>
-#include <inttypes.h>
-
-struct named_init_test {
-  int a;
-  int b;
-};
-
-extern void structfunc(struct named_init_test);
-
-int main(int argc, char **argv)
-{
-  struct named_init_test nit = {
-    .a = 3,
-    .b = 5,
-  };
-
-  for (int loop_var = 0; loop_var < 3; loop_var++)
-  {
-    nit.a += nit.b;
-  }
-
-  structfunc((struct named_init_test){1, 0});
-
-  return nit.a != 0;
-}
+# Do we need an option to enable C11?
+c11_test = '''
+#if !defined __STDC_VERSION__ || __STDC_VERSION__ < 201112L
+# error "Compiler does not advertise C11 conformance"
+#endif
 '''
 
-if not cc.compiles(c99_test, name: 'c99')
-  if cc.compiles(c99_test, name: 'c99 with -std=c99', args: ['-std=c99'])
-    cflags += '-std=c99'
+if not cc.compiles(c11_test, name: 'C11')
+  c11_ok = false
+  if cc.get_id() == 'msvc'
+    c11_test_args = ['/std:c11']
   else
-    error('C compiler does not support C99')
+    c11_test_args = ['-std=gnu11', '-std=c11']
+  endif
+  foreach arg : c11_test_args
+    if cc.compiles(c11_test, name: 'C11 with @0@'.format(arg), args: [arg])
+      c11_ok = true
+      cflags += arg
+      break
+    endif
+  endforeach
+  if not c11_ok
+    error('C compiler does not support C11')
   endif
 endif