https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111669
Bug ID: 111669
Summary: bogus -Wnonnull in conditionally executed code
Product: gcc
Version: 13.2.0
Status: UNCONFIRMED
Keywords: diagnostic
Severity: normal
Priority: P3
Component: middle-end
Assignee: unassigned at gcc dot gnu.org
Reporter: zfigura at codeweavers dot com
Target Milestone: ---
Created attachment 56032
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=56032&action=edit
reduced testcase, compile with -O2 -Werror=nonnull
Sorry about the rather useless title, but I can't really figure out what
actually triggers this error. It seems to depend on some arcane combination of
optimizations.
I was able to reduce this down to a pretty minimal test case, attached here. It
may be possible to reduce it further but I couldn't easily find a way.
The actual code that triggers this is here [1]. lstrcpyA() and lstrcatA() are
trivial wrappers around strcpy/strcat. The NULL comes from get_search_path() at
line 192. The offending strcpy/strcat will never be reached if
GetWindowsDirectoryA() returns nonzero, which it always should. However, gcc
triggers a -Wnonnull warning anyway.
Interestingly, the original Wine code only triggers the warning with
-march=bdver2 (or other values of -march), but the reduced testcase triggers it
with no -march flags.
[1]
https://source.winehq.org/git/wine.git/blob/HEAD:/dlls/krnl386.exe16/file.c#l639
