https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104851
Bug ID: 104851
Summary: off-by-one out-of-bound access in
supports_vec_convert_optab_p, at optabs-query.cc:725
Product: gcc
Version: 12.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: tree-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: xry111 at mengyan1223 dot wang
Target Milestone: ---
We have:
723: int end = mode == VOIDmode ? MAX_MACHINE_MODE : mode;
724: for (int i = start; i <= end; ++i)
725: if (VECTOR_MODE_P ((machine_mode) i))
Line 725, eventually expands to access mode_class[MAX_MACHINE_MODE] at the last
iteration when mode is VOIDmode. However, the number of elements of mode_class
is NUM_MACHINE_MODES, which equals to MAX_MACHINE_MODE. This causes ubsan
alerts like:
../../gcc/gcc/optabs-query.cc:725:9: runtime error: index 69 out of bounds for
type 'unsigned char [69]'
../../gcc/gcc/optabs-query.cc:725:9: runtime error: load of address
0x0126faa83d with insufficient space for an object of type 'const unsigned
char'
