configure.ac: check if flags are needed for c99

some older and more obscure compilers (e.g. mipspro on irix) default to the strictest standard they know instead of the most permissive. since libarchive uses c99 features in several places throughout, but does not pass appropriate cflags to parse c99 code, it will fail to compile from the configure script on these systems. this change will have autoconf check if any flags are needed for the c compiler to accept c99 code, and add them to cflags.

diff --git a/configure.ac b/configure.ac
index 7744365a59ae902210d8fa03cc653a2045dbb6ae..41ba5a49b962685d2c4f458d8d7c6b6d11a3b411 100644 (file)
--- a/configure.ac
+++ b/configure.ac
@@ -103,6 +103,7 @@ AC_SUBST(PLATFORMCPPFLAGS)
 
 # Checks for programs.
 AC_PROG_CC
+AC_PROG_CC_C99
 AM_PROG_CC_C_O
 AC_USE_SYSTEM_EXTENSIONS
 AC_LIBTOOL_WIN32_DLL