https://gcc.gnu.org/bugzilla/show_bug.cgi?id=125885
Bug ID: 125885
Summary: False -Warray-bounds array subscript above array
bounds with lookup table
Product: gcc
Version: 16.1.1
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: tree-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: thadhouse1 at gmail dot com
Target Milestone: ---
Created attachment 64777
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=64777&action=edit
Minimal Reproduction of the issue in C, self contained
After upgrading to GCC 16, we noticed one of the functions we import from LLVM
to convert UTF8 to UTF 16 was failing to compile with an array subscript out of
bounds error. We boiled the bug down to the attached code, where it seems like
static analysis is ignoring the fact that a Lookup Table is being used, and is
just assuming an array read is out of bounds.
Attached is a minimal reproduction that reproduces the issue.
It seems to be that GCC is not actually flowing through the Lookup Table, and
is instead assuming it can return an index that is out of range.
