stdio: warn on suspicious uses Using gets is almost ALWAYS wrong (it is extremely rare that you have full control over stdin). POSIX 2008 marked it as obsolete, even though C89 requires it. Attach a warning to remind developers. Add a comment to sprintf explaining why it does not get this treatment. Improve the warnings for fseek/fseeko (and ftell/ftello), with comments justifying our position. Some of our unit tests never use large files, so rather than drag in a dependency on fseeko, they should be the first compilation units to use _GL_NO_LARGE_FILES. * modules/stdio (Depends-on): Add warn-on-use. (Makefile.am): Provide new substitutions. * m4/stdio_h.m4 (gl_STDIO_H): Check for inline, ftello, and fseeko. * lib/stdio.in.h (gets): Always warn on use. (fseek, ftell): Adjust when warnings are issued, and honor _GL_NO_LARGE_FILES as a way to silence the warning. * tests/test-fpurge.c [!GNULIB_FSEEK]: Use new means to squelch any warning about large file offsets. * tests/test-freadable.c [!GNULIB_FSEEK]: Likewise. * tests/test-freading.c [!GNULIB_FSEEK]: Likewise. * tests/test-fseeko.c [!GNULIB_FSEEK]: Likewise. * tests/test-ftell.c [!GNULIB_FSEEK]: Likewise. * tests/test-ftello.c [!GNULIB_FSEEK]: Likewise. * tests/test-fwritable.c [!GNULIB_FSEEK]: Likewise. * tests/test-fwriting.c [!GNULIB_FSEEK]: Likewise. * tests/test-getopt.c [!GNULIB_FTELL]: Likewise. Signed-off-by: Eric Blake <ebb9@byu.net>

--- a/tests/test-freading.c
+++ b/tests/test-freading.c
@@ -18,18 +18,15 @@
 
 #include <config.h>
 
+/* None of the files accessed by this test are large, so disable the
+   fseek link warning if we are not using the gnulib fseek module.  */
+#define _GL_NO_LARGE_FILES
 #include "freading.h"
 
 #include <stdio.h>
 
 #include "macros.h"
 
-/* None of the files accessed by this test are large, so disable the
-   fseek link warning if we are not using the gnulib fseek module.  */
-#if !GNULIB_FSEEK
-# undef fseek
-#endif
-
 #define TESTFILE "t-freading.tmp"
 
 int