https://github.com/westes/flex/issues/539 https://github.com/westes/flex/pull/554 https://bugs.gentoo.org/871324 This is a backported version for applying to v2.6.4 instead of git. From cce2df853386d5b5b60445b1204dcca08e9f259e Mon Sep 17 00:00:00 2001 From: Yifeng Li Date: Mon, 20 Feb 2023 11:23:52 +0000 Subject: [PATCH] Fix #539 crash on Apple M1 by casting 0 to (char *) explicitly Currently, when the NULL-terminated variadic function filter_create_ext() is invoked, the value "0" is passed as the last argument to act as a terminator. However, this is an integer value, which is incompatible with the pointer data type expected by filter_create_ext(). This is undefined behavior in C, correct operation is not guaranteed. In fact, it causes flex to crash on Apple M1 when GCC is used - the loop is not terminated when it should, instead, it keeps running, corrupting the argument list for invoking m4. As a result, it creates the following error: > flex: fatal internal error, exec of gm4 failed This commit fixes the problem by explicitly casting the value 0 to the correct pointer type (char *). Signed-off-by: Yifeng Li --- src/main.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/src/main.c b/src/main.c index e5eac44fe..5c9086183 100644 --- a/src/main.c +++ b/src/main.c @@ -380,7 +380,7 @@ void check_options (void) } } } - filter_create_ext(output_chain, m4, "-P", 0); + filter_create_ext(output_chain, m4, "-P", (char *) 0); filter_create_int(output_chain, filter_fix_linedirs, NULL); /* For debugging, only run the requested number of filters. */