--- a/configure.in
+++ b/configure.in
@@ -21,9 +21,11 @@ image_formats="GIF PNG XBM"
 AM_CONFIG_HEADER(config.h)
 
 dnl Checks for programs.
-AC_PROG_CC
+AC_PROG_CC_STDC
+AC_USE_SYSTEM_EXTENSIONS
+AC_SYS_LARGEFILE
 
-dnl AC_PROG_CXX
+AC_PROG_CXX
 dnl AC_PROG_AWK
 dnl AM_PROG_LEX
 dnl AC_PROG_YACC