Added a macro and code that checks for the %a format string in sprintf().

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@9089 91177308-0d34-0410-b5e6-96231b3b80d8

autoconf/aclocal.m4

@@ -6166,4 +6166,33 @@ AC_DEFUN([AC_CONFIG_MAKEFILE],
 [AC_CONFIG_COMMANDS($1,${SHELL} ${srcdir}/autoconf/install-sh -c ${srcdir}/$1 $1,${srcdir}/autoconf/mkinstalldirs `dirname $1`)
 ])
 
+#
+# Determine if the printf() functions have the %a format character.
+# This is modified from:
+# http://www.gnu.org/software/ac-archive/htmldoc/ac_cxx_have_ext_slist.html
+AC_DEFUN([AC_C_PRINTF_A],
+[
+	AC_LANG_SAVE
+	AC_LANG_C
+	AC_RUN_IFELSE(
+		AC_LANG_PROGRAM([#include <stdio.h>
+		                 #include <stdlib.h>],
+		                 [[[
+		                 volatile double A, B;
+		                 char Buffer[100];
+		                 A = 1;
+		                 A /= 10.0;
+		                 sprintf(Buffer, "%a", A);
+		                 B = atof(Buffer);
+		                 if (A != B)
+							 return (1);
+		                 if (A != 0x1.999999999999ap-4)
+							 return (1);
+		                 return (0);]]]),
+		ac_c_printf_a=yes,ac_c_printf_a=no)
+	AC_LANG_RESTORE
+	if test "$ac_c_printf_a" = "yes"; then
+		AC_DEFINE([HAVE_PRINTF_A],[1],[Define to have the %a format string])
+	fi
+])
 

autoconf/configure.ac

@@ -455,6 +455,9 @@ AC_CHECK_TYPES([uint64_t],,AC_MSG_ERROR([Type uint64_t required but not found]))
 AC_HEADER_TIME
 AC_STRUCT_TM
 
+dnl Check for various C features
+AC_C_PRINTF_A
+
 dnl Check for C++ extensions
 AC_CXX_HAVE_EXT_HASH_MAP
 AC_CXX_HAVE_EXT_HASH_SET