X-Git-Url: https://git.saurik.com/bison.git/blobdiff_plain/a4e4295ad2c737bb64fc0b1fcb164a15e6b1f281..a0cd287e64e2d53bc5896e0a7c5ad072cb8bf469:/m4/flex.m4

diff --git a/m4/flex.m4 b/m4/flex.m4
index 7e1b914e..984c5143 100644
--- a/m4/flex.m4
+++ b/m4/flex.m4
@@ -1,4 +1,4 @@
-# flex.m4 serial 1
+# flex.m4 serial 2
 # Copyright (C) 2012 Free Software Foundation, Inc.
 # This file is free software; the Free Software Foundation
 # gives unlimited permission to copy and/or distribute it,
@@ -20,10 +20,27 @@ fi])
 
 # _AC_PROG_LEX_YYTEXT_DECL
 # ------------------------
-# Check for the Lex output root, the Lex library, and whether Lex
-# declares yytext as a char * by default.
+# Check whether this is Flex, for the Lex output root, the Lex library,
+# and whether Lex declares yytext as a char * by default.
 m4_define([_AC_PROG_LEX_YYTEXT_DECL],
+[AC_CACHE_CHECK([whether lex is flex],
+                [ac_cv_prog_lex_is_flex],
 [cat >conftest.l <<_ACEOF[
+%option debug nodefault noinput nounput noyywrap never-interactive
+%x SC_CONF_TEST
+%%
+a { BEGIN SC_CONF_TEST; }
+]_ACEOF
+if _AC_DO_VAR([LEX conftest.l]); then
+  ac_cv_prog_lex_is_flex=yes
+else
+  ac_cv_prog_lex_is_flex=no
+fi
+])
+AC_SUBST([LEX_IS_FLEX],
+         [`test "$ac_cv_prog_lex_is_flex" = yes && echo true || echo false`])dnl
+
+cat >conftest.l <<_ACEOF[
 %%
 a { ECHO; }
 b { REJECT; }