(AC_FUNC_SETVBUF_REVERSED):

If prototypes are supported, use them to check this at compile-time,
instead of trying to check it at run-time.  If we must do a run-time
check, assume that setvbuf is standard when cross-compiling, as
nonstandard setvbuf occurs only on ancient and unlikely hosts.

diff --git a/lib/autoconf/functions.m4 b/lib/autoconf/functions.m4
index 1d7235944962be27986c4982b42bf0213a024877..b059cffe2ecb2b149418ae1111f86a05b3c8d8a7 100644 (file)
--- a/lib/autoconf/functions.m4
+++ b/lib/autoconf/functions.m4
@@ -1295,22 +1295,42 @@ test $ac_cv_func_strnlen_working = no && AC_LIBOBJ([strnlen])
 # AC_FUNC_SETVBUF_REVERSED
 # ------------------------
 AC_DEFUN([AC_FUNC_SETVBUF_REVERSED],
-[AC_CACHE_CHECK(whether setvbuf arguments are reversed,
+[AC_REQUIRE([AC_C_PROTOTYPES])dnl
+AC_CACHE_CHECK(whether setvbuf arguments are reversed,
   ac_cv_func_setvbuf_reversed,
-[AC_TRY_RUN([#include <stdio.h>
-/* If setvbuf has the reversed format, exit 0. */
-int
-main ()
-{
-  /* This call has the arguments reversed.
-     A reversed system may check and see that the address of main
-     is not _IOLBF, _IONBF, or _IOFBF, and return nonzero.  */
-  if (setvbuf(stdout, _IOLBF, (char *) main, BUFSIZ) != 0)
-    exit(1);
-  putc('\r', stdout);
-  exit(0);                     /* Non-reversed systems segv here.  */
-}], ac_cv_func_setvbuf_reversed=yes, ac_cv_func_setvbuf_reversed=no)
-rm -f core core.* *.core])
+  [ac_cv_func_setvbuf_reversed=no
+   AC_LINK_IFELSE(
+     [AC_LANG_PROGRAM(
+       [[#include <stdio.h>
+#        if PROTOTYPES
+          int (setvbuf) (FILE *, int, char *, size_t);
+#        endif]],
+       [[char buf; return setvbuf (stdout, _IOLBF, &buf, 1);]])],
+     [AC_LINK_IFELSE(
+       [AC_LANG_PROGRAM(
+          [[#include <stdio.h>
+#           if PROTOTYPES
+             int (setvbuf) (FILE *, int, char *, size_t);
+#           endif]],
+          [[char buf; return setvbuf (stdout, &buf, _IOLBF, 1);]])],
+       [# It compiles and links either way, so it must not be declared
+        # with a prototype and most likely this is a K&R C compiler.
+        # Try running it.
+        AC_RUN_IFELSE(
+          [AC_LANG_PROGRAM(
+             [[#include <stdio.h>]],
+             [[/* This call has the arguments reversed.
+                  A reversed system may check and see that the address of buf
+                  is not _IOLBF, _IONBF, or _IOFBF, and return nonzero.  */
+               char buf;
+               if (setvbuf (stdout, _IOLBF, &buf, 1) != 0)
+                 exit (1);
+               putchar ('\r');
+               exit (0); /* Non-reversed systems SEGV here.  */]])],
+          ac_cv_func_setvbuf_reversed=yes,
+          rm -f core core.* *.core,
+          [[: # Assume setvbuf is not reversed when cross-compiling.]])]
+       ac_cv_func_setvbuf_reversed=yes)])])
 if test $ac_cv_func_setvbuf_reversed = yes; then
   AC_DEFINE(SETVBUF_REVERSED, 1,
             [Define to 1 if the `setvbuf' function takes the buffering type as