https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99418
Martin Sebor <msebor at gcc dot gnu.org> changed: What |Removed |Added ---------------------------------------------------------------------------- Blocks| |56456 Status|WAITING |NEW Keywords| |diagnostic --- Comment #9 from Martin Sebor <msebor at gcc dot gnu.org> --- I don't know enough about the sanitizer to judge how difficult it might be to handle this case but a patch I posted in November (https://gcc.gnu.org/pipermail/gcc-patches/2020-November/558775.html) enhances -Warray-bounds to diagnose the test cases in comment #8: $ g++ -O2 -S -Wall pr99418-c8.C pr99418-c8.C: In function ‘void f()’: pr99418-c8.C:7:10: warning: unused variable ‘p’ [-Wunused-variable] 7 | int& p = a[10]; // (1) | ^ pr99418-c8.C:8:6: warning: subscript 10 in argument 1 to ‘void g(int&)’ is just past the end of ‘int [10]’ [-Warray-bounds] 8 | g(a[10]); // (2) | ~^~~~~~~ pr99418-c8.C:6:9: note: at offset 40 into source object ‘a’ of size 40 6 | int a[10]; | ^ The enhancement doesn't handle multidimensional VLAs like those in comment #1 but it looks like the IL has enough information to make the detection possible: int main () { int[0:D.2590][0:D.2587] * mas.4; int * _4; <bb 2> [local count: 1073741824]: mas.4_3 = __builtin_alloca_with_align (48, 32); _4 = &MEM <int[0:D.2590][0:D.2587]> [(int[0:D.2569][0:D.2565] *)mas.4_3][3]{lb: 0 sz: 12}[3]; escape (_4); return 0; } With that let me confirm this request for both -Warray-bounds (I'll resubmit the patch for GCC 12) and for the sanitizer. Referenced Bugs: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=56456 [Bug 56456] [meta-bug] bogus/missing -Warray-bounds