Backporting AC_PROG_CC_C99 macro for redhat.

RedHat 5.4 (and CentOS) ship with 2.59 which doesn't have the
AC_PROG_CC_C99 macro necessary for detecting C99 flags for the
compiler.

configure.ac

@@ -1,6 +1,7 @@
 AC_PREREQ(2.52)
 m4_include([version.m4])
-AC_INIT(memcached, VERSION_NUMBER, [email protected])
+m4_include([m4/c99-backport.m4])
+AC_INIT(memcached, VERSION_NUMBER, [email protected])
 AC_CANONICAL_SYSTEM
 AC_CONFIG_SRCDIR(memcached.c)
 AM_INIT_AUTOMAKE(AC_PACKAGE_NAME, AC_PACKAGE_VERSION)

m4/c99-backport.m4

@@ -0,0 +1,188 @@
+# AC_PROG_CC_C99 ([ACTION-IF-AVAILABLE], [ACTION-IF-UNAVAILABLE])
+# ----------------------------------------------------------------
+# If the C compiler is not in ISO C99 mode by default, try to add an
+# option to output variable CC to make it so.  This macro tries
+# various options that select ISO C99 on some system or another.  It
+# considers the compiler to be in ISO C99 mode if it handles _Bool,
+# // comments, flexible array members, inline, long long int, mixed
+# code and declarations, named initialization of structs, restrict,
+# va_copy, varargs macros, variable declarations in for loops and
+# variable length arrays.
+AC_DEFUN([AC_PROG_CC_C99],
+[AC_C_STD_TRY([c99],
+[[#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;
+#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);
+}
+]],
+[[
+  // 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);
+]],
+dnl Try
+dnl GCC		-std=gnu99 (unused restrictive modes: -std=c99 -std=iso9899:1999)
+dnl AIX		-qlanglvl=extc99 (unused restrictive mode: -qlanglvl=stdc99)
+dnl Intel ICC	-c99
+dnl IRIX	-c99
+dnl Solaris	(unused because it causes the compiler to assume C99 semantics for
+dnl		library functions, and this is invalid before Solaris 10: -xc99)
+dnl Tru64	-c99
+dnl with extended modes being tried first.
+[[-std=gnu99 -c99 -qlanglvl=extc99]], [$1], [$2])[]dnl
+])# AC_PROG_CC_C99
+
+# AC_C_STD_TRY(STANDARD, TEST-PROLOGUE, TEST-BODY, OPTION-LIST,
+#		ACTION-IF-AVAILABLE, ACTION-IF-UNAVAILABLE)
+# --------------------------------------------------------------
+# Check whether the C compiler accepts features of STANDARD (e.g `c89', `c99')
+# by trying to compile a program of TEST-PROLOGUE and TEST-BODY.  If this fails,
+# try again with each compiler option in the space-separated OPTION-LIST; if one
+# helps, append it to CC.  If eventually successful, run ACTION-IF-AVAILABLE,
+# else ACTION-IF-UNAVAILABLE.
+AC_DEFUN([AC_C_STD_TRY],
+[AC_MSG_CHECKING([for $CC option to accept ISO ]m4_translit($1, [c], [C]))
+AC_CACHE_VAL(ac_cv_prog_cc_$1,
+[ac_cv_prog_cc_$1=no
+ac_save_CC=$CC
+AC_LANG_CONFTEST([AC_LANG_PROGRAM([$2], [$3])])
+for ac_arg in '' $4
+do
+  CC="$ac_save_CC $ac_arg"
+  _AC_COMPILE_IFELSE([], [ac_cv_prog_cc_$1=$ac_arg])
+  test "x$ac_cv_prog_cc_$1" != "xno" && break
+done
+rm -f conftest.$ac_ext
+CC=$ac_save_CC
+])# AC_CACHE_VAL
+case "x$ac_cv_prog_cc_$1" in
+  x)
+    AC_MSG_RESULT([none needed]) ;;
+  xno)
+    AC_MSG_RESULT([unsupported]) ;;
+  *)
+    CC="$CC $ac_cv_prog_cc_$1"
+    AC_MSG_RESULT([$ac_cv_prog_cc_$1]) ;;
+esac
+AS_IF([test "x$ac_cv_prog_cc_$1" != xno], [$5], [$6])
+])# AC_C_STD_TRY

t/whitespace.t

@@ -9,6 +9,7 @@ BEGIN {
     my @exempted = qw(Makefile.am ChangeLog doc/Makefile.am);
     push(@exempted, glob("doc/*.xml"));
     push(@exempted, glob("doc/xml2rfc/*.xsl"));
+    push(@exempted, glob("m4/*backport*m4"));
     my %exempted_hash = map { $_ => 1 } @exempted;
 
     my @stuff = split /\0/, `git ls-files -z -c -m -o --exclude-standard`;