https://gcc.gnu.org/bugzilla/show_bug.cgi?id=119070
Bug ID: 119070
Summary: gcc15 incorrectly reporting negative array-bounds
errors
Product: gcc
Version: 15.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
Assignee: unassigned at gcc dot gnu.org
Reporter: taylor.hutt at broadcom dot com
Target Milestone: ---
The code in 'cit.c' has been extracted from a production audio driver
present in widely used virtualization products.
The code has not been meaningfully changed in many years.
The gcc version banner is:
x86_64-vmw-linux-gnu-gcc (crosstool-NG 1.26.0.127_1c395b2) 15.0.1 20250227
(experimental)
Copyright (C) 2025 Free Software Foundation, Inc.
This is free software; see the source for copying conditions. There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
The code was checked out using crosstool-ng at the top of the 'master'
branch on the day of the build.
The script 'citi' (with modifications to produce a path to gcc15) will
reproduce the errors. The errors are as follows:
/tmp/gcc15/cit.c: In function 'function_1':
/tmp/gcc15/cit.c:27:19: error: array subscript -227 is outside array bounds
of 'struct_2[1]' [-Werror=array-bounds=]
27 | unsigned char *v3 = v2 - 0x2000;
| ^~
/tmp/gcc15/cit.c:16:17: note: at offset -8192 into object 'global_0' of size
36
16 | extern struct_2 global_0;
| ^~~~~~~~
/tmp/gcc15/cit.c:27:19: error: array subscript -227 is outside array bounds
of 'struct_2[1]' [-Werror=array-bounds=]
27 | unsigned char *v3 = v2 - 0x2000;
| ^~
/tmp/gcc15/cit.c:16:17: note: at offset -8192 into object 'global_0' of size
36
16 | extern struct_2 global_0;
| ^~~~~~~~
/tmp/gcc15/cit.c:27:19: error: array subscript -227 is outside array bounds
of 'struct_2[1]' [-Werror=array-bounds=]
27 | unsigned char *v3 = v2 - 0x2000;
| ^~
/tmp/gcc15/cit.c:16:17: note: at offset -8192 into object 'global_0' of size
36
16 | extern struct_2 global_0;
| ^~~~~~~~
cc1: all warnings being treated as errors
I find, using https://godbolt.org/, that the regression was introduced
in gcc10. The code compiles without issue with gcc9.
