Don't use IF_LINT in Bison sources.

It creates unnecessary differences between the sources that Bison
maintainers build and test (given that maintainers normally
configure with --enable-gcc-warnings) and the sources that Bison
users build.  Instead, use PACIFY_CC, which doesn't.  This change
fixes compiler warnings reported by Tys Lefering at
<http://lists.gnu.org/archive/html/bison-patches/2011-05/msg00004.html>.
* configure.ac: Don't AC_DEFINE lint regardless of the configure
options.  This change affects imported gnulib sources, where
IF_LINT still appears and depends on lint.
* src/scan-gram.l, src/scan-skel.l: Replace uses of IF_LINT with
PACIFY_CC.
* src/system.h (IF_LINT): Remove cpp macro.
(PACIFY_CC): New cpp macro.

1 files changed, 13 insertions, 7 deletions

diff --git a/src/system.h b/src/system.h
index 97a92257..13669a40 100644
--- a/src/system.h
+++ b/src/system.h
@@ -66,13 +66,19 @@ typedef size_t uintptr_t;
 | GCC extensions.  |
 `-----------------*/
 
-/* Use this to suppress gcc's `...may be used before initialized'
-   warnings.  */
-#ifdef lint
-# define IF_LINT(Code) Code
-#else
-# define IF_LINT(Code) /* empty */
-#endif
+/* Use PACIFY_CC to indicate that Code is unimportant to the logic of Bison
+   but that it is necessary for suppressing compiler warnings.  For example,
+   Code might be a variable initializer that's always overwritten before the
+   variable is used.
+
+   PACIFY_CC is intended to be useful only as a comment as it does not alter
+   Code.  It is tempting to redefine PACIFY_CC so that it will suppress Code
+   when configuring without --enable-gcc-warnings.  However, that would mean
+   that, for maintainers, Bison would compile with potentially less warnings
+   and safer logic than it would for users.  Due to the overhead of M4,
+   suppressing Code is unlikely to offer any significant improvement in
+   Bison's performance anyway.  */
+#define PACIFY_CC(Code) Code
 
 #ifndef __attribute__
 /* This feature is available in gcc versions 2.5 and later.  */