warn-on-use: use instead of link-warning

Each *.in.h file serves two purposes - provide enough self-contained
content to serve as a replacement for the system header regardless of
the user's compiler, and offer the developer the ability to detect any
gnulib modules that might have been inadvertantly excluded.  The
former requires independence from config.h, and routes everything
through a Makefile.am snippet that uses @@ substitution specific to
the modules that were in use, with details learned at configure time.

The latter works by poisoning anything that gnulib did not replace,
but which the developer had natively available, explaining why their
tests passed during development.  Poisoning relies on gcc features,
and requires manual triggering by adding -DGNULIB_POSIXCHECK to
CFLAGS; it assumes that <config.h> is properly included.  In fact, we
do not want to use @@ substitution for HAVE_DECL_* during poisoning,
because the warning is only relevant for the gnulib modules which were
not included, and thus where the m4 macros to set proper @@ values
have not been run.  Furthermore, we only need to poison interfaces
that already have a declaration; if something is not declared, then
the developer wouldn't have been able to link, so their code won't be
using the problematic interface in the first place.

* modules/stdio (Depends-on, Makefile.am): Drop link-warning.
* modules/unistd (Depends-on, Makefile.am): Likewise.
* modules/arpa_inet (Depends-on): Replace link-warning with
warn-on-use.
(Makefile.am): Update rules accordingly.
* modules/ctype (Depends-on, Makefile.am): Likewise.
* modules/dirent (Depends-on, Makefile.am): Likewise.
* modules/fcntl-h (Depends-on, Makefile.am): Likewise.
* modules/inttypes (Depends-on, Makefile.am): Likewise.
* modules/langinfo (Depends-on, Makefile.am): Likewise.
* modules/locale (Depends-on, Makefile.am): Likewise.
* modules/math (Depends-on, Makefile.am): Likewise.
* modules/search (Depends-on, Makefile.am): Likewise.
* modules/signal (Depends-on, Makefile.am): Likewise.
* modules/spawn (Depends-on, Makefile.am): Likewise.
* modules/stdlib (Depends-on, Makefile.am): Likewise.
* modules/string (Depends-on, Makefile.am): Likewise.
* modules/strings (Depends-on, Makefile.am): Likewise.
* modules/sys_file (Depends-on, Makefile.am): Likewise.
* modules/sys_ioctl (Depends-on, Makefile.am): Likewise.
* modules/sys_select (Depends-on, Makefile.am): Likewise.
* modules/sys_socket (Depends-on, Makefile.am): Likewise.
* modules/sys_stat (Depends-on, Makefile.am): Likewise.
* modules/sys_times (Depends-on, Makefile.am): Likewise.
* modules/sys_utsname (Depends-on, Makefile.am): Likewise.
* modules/wchar (Depends-on, Makefile.am): Likewise.
* m4/arpa_inet_h.m4 (gl_HEADER_ARPA_INET): Check which functions
should be poisoned.
* m4/ctype.m4 (gl_CTYPE_H): Likewise.
* m4/dirent_h.m4 (gl_DIRENT_H): Likewise.
* m4/fcntl_h.m4 (gl_FCNTL_H): Likewise.
* m4/inttypes.m4 (gl_INTTYPES_H): Likewise.
* m4/langinfo_h.m4 (gl_LANGINFO_H): Likewise.
* m4/locale_h.m4 (gl_LOCALE_H): Likewise.
* m4/math_h.m4 (gl_MATH_H): Likewise.
* m4/search_h.m4 (gl_SEARCH_H): Likewise.
* m4/signal_h.m4 (gl_SIGNAL_H): Likewise.
* m4/spawn_h.m4 (gl_SPAWN_H): Likewise.
* m4/stdio_h.m4 (gl_STDIO_H): Likewise.
* m4/stdlib_h.m4 (gl_STDLIB_H): Likewise.
* m4/string_h.m4 (gl_HEADER_STRING_H_BODY): Likewise.
* m4/strings_h.m4 (gl_HEADER_STRINGS_H_BODY): Likewise.
* m4/sys_file_h.m4 (gl_HEADER_SYS_FILE_H_DEFAULTS): Likewise.
* m4/sys_ioctl_h.m4 (gl_SYS_IOCTL_H): Likewise.
* m4/sys_select_h.m4 (gl_HEADER_SYS_SELECT): Likewise.
* m4/sys_socket_h.m4 (gl_HEADER_SYS_SOCKET): Likewise.
* m4/sys_stat_h.m4 (gl_HEADER_SYS_STAT_H): Likewise.
* m4/sys_times_h.m4 (gl_SYS_TIMES_H): Likewise.
* m4/sys_utsname_h.m4 (gl_SYS_UTSNAME_H): Likewise.
* m4/unistd_h.m4 (gl_UNISTD_H): Likewise.
* m4/wchar.m4 (gl_WCHAR_H): Likewise.
* lib/arpa_inet.in.h: Use _GL_WARN_ON_USE instead of
GL_LINK_WARNING.
* lib/ctype.in.h: Likewise.
* lib/dirent.in.h: Likewise.
* lib/fcntl.in.h: Likewise.
* lib/inttypes.in.h: Likewise.
* lib/langinfo.in.h: Likewise.
* lib/locale.in.h: Likewise.
* lib/math.in.h: Likewise.
* lib/search.in.h: Likewise.
* lib/signal.in.h: Likewise.
* lib/spawn.in.h: Likewise.
* lib/stdio.in.h: Likewise.
* lib/stdlib.in.h: Likewise.
* lib/string.in.h: Likewise.
* lib/strings.in.h: Likewise.
* lib/sys_file.in.h: Likewise.
* lib/sys_ioctl.in.h: Likewise.
* lib/sys_select.in.h: Likewise.
* lib/sys_socket.in.h: Likewise.
* lib/sys_stat.in.h: Likewise.
* lib/sys_times.in.h: Likewise.
* lib/sys_utsname.in.h: Likewise.
* lib/unistd.in.h: Likewise.
* lib/wchar.in.h: Likewise.

Signed-off-by: Eric Blake <ebb9@byu.net>

1 files changed, 13 insertions, 14 deletions

diff --git a/lib/fcntl.in.h b/lib/fcntl.in.h
index b0a90fc746..a1d9e23087 100644
--- a/lib/fcntl.in.h
+++ b/lib/fcntl.in.h
@@ -50,10 +50,10 @@
 #endif
 
 
-/* The definition of GL_LINK_WARNING is copied here.  */
-
 /* The definition of _GL_ARG_NONNULL is copied here.  */
 
+/* The definition of _GL_WARN_ON_USE is copied here.  */
+
 
 /* Declare overridden functions.  */
 
@@ -71,10 +71,10 @@ extern int fcntl (int fd, int action, ...);
 # endif
 #elif defined GNULIB_POSIXCHECK
 # undef fcntl
-# define fcntl \
-    (GL_LINK_WARNING ("fcntl is not always POSIX compliant - " \
-                      "use gnulib module fcntl for portability"), \
-     fcntl)
+# if HAVE_RAW_DECL_FCNTL
+_GL_WARN_ON_USE (fcntl, "fcntl is not always POSIX compliant - "
+                 "use gnulib module fcntl for portability");
+# endif
 #endif
 
 #if @GNULIB_OPEN@
@@ -85,10 +85,9 @@ extern int open (const char *filename, int flags, ...) _GL_ARG_NONNULL ((1));
 # endif
 #elif defined GNULIB_POSIXCHECK
 # undef open
-# define open \
-    (GL_LINK_WARNING ("open is not always POSIX compliant - " \
-                      "use gnulib module open for portability"), \
-     open)
+/* Assume open is always declared.  */
+_GL_WARN_ON_USE (open, "open is not always POSIX compliant - "
+                 "use gnulib module open for portability");
 #endif
 
 #if @GNULIB_OPENAT@
@@ -102,10 +101,10 @@ extern int openat (int fd, char const *file, int flags, /* mode_t mode */ ...)
 # endif
 #elif defined GNULIB_POSIXCHECK
 # undef openat
-# define openat \
-    (GL_LINK_WARNING ("openat is not portable - " \
-                      "use gnulib module openat for portability"), \
-     openat)
+# if HAVE_RAW_DECL_OPENAT
+_GL_WARN_ON_USE (openat, "openat is not portable - "
+                 "use gnulib module openat for portability");
+# endif
 #endif
 
 #ifdef __cplusplus