build: do not prototype flex-generated functions.

Some versions of Flex, possibly modified by the distribution package
maintainers, have incompatible signatures.  Since newer versions of
Flex prototype their functions, avoid the conflicts in that case.
Reported by Stefano Lattarini.
<http://lists.gnu.org/archive/html/bug-bison/2012-05/msg00012.html>.

* src/flex-scanner.h (FLEX_VERSION_GT): New.
Use it to issue prototypes for flex-generated functions only for
versions up to 2.5.31, in accordance with the comment.
See commit dc9701e848f27ae64b6ddcf809580998667d60f2.
Use it to define yylex_destroy when needed.

diff --git a/NEWS b/NEWS
index b56746e6becd5e249278460766a735d6b88aa99b..f554b9ff29865a430eeee9215ea7e247512f14cf 100644 (file)
--- a/NEWS
+++ b/NEWS
@@ -59,7 +59,13 @@ Bison News
   format.  Incorrect index entries were fixed.  Some other errors were
   fixed.
 
-** Changes to the build system:
+** Building bison:
+
+*** Conflicting prototypes with recent/modified Flex.
+
+  Fixed build problems with the current, unreleased, version of Flex,
+  and some modified versions of 2.5.35, which have modified function
+  prototypes.
 
 *** Warnings during the build procedure have been eliminated.
 

diff --git a/src/flex-scanner.h b/src/flex-scanner.h
index 23a266ac54e2683396f2bd3324551548a0cacc56..f27938dc6253bbfb51eaefa388419eb6f52dfb43 100644 (file)
--- a/src/flex-scanner.h
+++ b/src/flex-scanner.h
@@ -21,7 +21,20 @@
 # error "FLEX_PREFIX not defined"
 #endif
 
+/* Whether this version of Flex is (strictly) greater than
+   Major.Minor.Subminor.  */
+#define FLEX_VERSION_GT(Major, Minor, Subminor)                         \
+  (defined YY_FLEX_MAJOR_VERSION                                        \
+   && (Major < YY_FLEX_MAJOR_VERSION                                    \
+       || (Major == YY_FLEX_MAJOR_VERSION                               \
+           && (defined YY_FLEX_MINOR_VERSION                            \
+               && (Minor < YY_FLEX_MINOR_VERSION                        \
+                   || (Minor == YY_FLEX_MINOR_VERSION                   \
+                       && defined YY_FLEX_SUBMINOR_VERSION              \
+                       && Subminor < YY_FLEX_SUBMINOR_VERSION))))))
+
 /* Pacify "gcc -Wmissing-prototypes" when flex 2.5.31 is used.  */
+# if ! FLEX_VERSION_GT (2, 5, 31)
 int   FLEX_PREFIX (get_lineno) (void);
 FILE *FLEX_PREFIX (get_in) (void);
 FILE *FLEX_PREFIX (get_out) (void);
@@ -33,6 +46,7 @@ void  FLEX_PREFIX (set_out) (FILE *);
 int   FLEX_PREFIX (get_debug) (void);
 void  FLEX_PREFIX (set_debug) (int);
 int   FLEX_PREFIX (lex_destroy) (void);
+#endif
 
 #define last_string    FLEX_PREFIX (last_string)
 
@@ -51,12 +65,7 @@ int   FLEX_PREFIX (lex_destroy) (void);
    versions according to the Flex manual) leak memory if yylex_destroy is not
    invoked.  However, yylex_destroy is not defined before Flex 2.5.9, so give
    an implementation here that at least appears to work with Flex 2.5.4.  */
-#if !defined YY_FLEX_MAJOR_VERSION || YY_FLEX_MAJOR_VERSION < 2 \
-    || (YY_FLEX_MAJOR_VERSION == 2 \
-        && (!defined YY_FLEX_MINOR_VERSION || YY_FLEX_MINOR_VERSION < 5 \
-            || (YY_FLEX_MINOR_VERSION == 5 \
-                && (!defined YY_FLEX_SUBMINOR_VERSION \
-                    || YY_FLEX_SUBMINOR_VERSION < 9))))
+#if ! FLEX_VERSION_GT (2, 5, 9)
 # define yylex_destroy() yy_delete_buffer (YY_CURRENT_BUFFER)
 #endif