https://gcc.gnu.org/bugzilla/show_bug.cgi?id=117482
Bug ID: 117482
Summary: Bogus -Wstringop-overflow warning in intrusive list
implementation
Product: gcc
Version: 14.2.1
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
Assignee: unassigned at gcc dot gnu.org
Reporter: adam at adamrosenfield dot com
Target Milestone: ---
Created attachment 59555
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=59555&action=edit
Test file exhibiting the bogus -Wstringop-overflow warning
In the attached code, we have an intrusive linked list implementation that
generates bogus -Wstringop-overflow warning.
Compile as:
```
$ gcc -c bug.c -Wall -O3
bug.c: In function ‘foo’:
bug.c:55:10: warning: writing 1 byte into a region of size 0
[-Wstringop-overflow=]
55 | x->a = 0;
| ~~~~~^~~
```
This occurs in every GCC version since 12.1. This occurs at -O2 and -O3, but
not at -O1 or -Os.
It's fairly sensitive to local code changes. If the `x->a` member is read from
instead of written into, it doesn't trigger. If there's another access of
`x->a` prior to the write, it doesn't trigger. If the type of `a` is changed
to a type with any other size (short/int/long long/etc.), it doesn't trigger.
If other fields are added or removed, or if the type of the `head` field as
changed, it doesn't trigger.
I've found a number of other -Wstringop-overflow bugs related to from the
metabug at https://gcc.gnu.org/bugzilla/show_bug.cgi?id=Wstringop-overflow, and
I looked through some of them, but I haven't exhaustively checked them all
since there are so many. If this is a duplicate of an existing issue, please
feel free to link this & resolve as a duplicate if needed.
