https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105420
Bug ID: 105420
Summary: Bogus -Warray-bounds with non-compile time-constant
variable
Product: gcc
Version: 12.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: tree-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: byteslice at airmail dot cc
Target Milestone: ---
Created attachment 52894
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=52894&action=edit
Reduced example
On gcc 12.0.1 20220413 (Fedora 36 Beta), with c++ -O1 -fexpensive-optimizations
-ftree-vrp -Werror=array-bounds, the attachment fails to compile, with the
following message:
<source>: In function 'void Initialize(int)':
<source>:9:53: error: array subscript -1 is below array bounds of 'int [8]'
[-Werror=array-bounds]
9 | int phys_core = VirtualToPhysicalCoreMap[virt_core];
| ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^
<source>:2:5: note: while referencing 'VirtualToPhysicalCoreMap'
2 | int VirtualToPhysicalCoreMap[8];
| ^~~~~~~~~~~~~~~~~~~~~~~~
cc1plus: some warnings being treated as errors
Compiler returned: 1
virt_core does not have a compile time-constant evaluation, so this warning is
bogus. The bogus warning does not appear in older versions of GCC.
Removing either -fexpensive-optimizations or -ftree-vrp allows compilation to
succeed.
