https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96384
Bug ID: 96384 Summary: [11 Regression] bogus -Wstringop-overflow= storing into multidimensional array with index in range Product: gcc Version: 11.0 Status: UNCONFIRMED Severity: normal Priority: P3 Component: middle-end Assignee: unassigned at gcc dot gnu.org Reporter: msebor at gcc dot gnu.org Target Milestone: --- The following test case triggers a false positive -Wstringop-overflow: $ cat z.c && gcc -O2 -S -Wall -fdump-tree-strlen-all=/dev/stdout z.c char a[2][3]; void f (unsigned i) { if (i > ~0U - 1) i = ~0U - 1; a[i][0] = 0; } ;; Function f (f, funcdef_no=0, decl_uid=1932, cgraph_uid=1, symbol_order=1) Pass statistics of "strlen": ---------------- ;; 1 loops found ;; ;; Loop 0 ;; header 0, latch 1 ;; depth 0, outer -1 ;; nodes: 0 1 2 ;; 2 succs { 1 } extract_range_from_stmt visiting: # RANGE [0, 4294967294] _2 = MIN_EXPR <i_1(D), 4294967294>; Intersecting unsigned int [0, 4294967294] and unsigned int [0, 4294967294] to unsigned int [0, 4294967294] z.c: In function âfâ: z.c:7:11: warning: writing 1 byte into a region of size 0 [-Wstringop-overflow=] 7 | a[i][0] = 0; | ~~~~~~~~^~~ z.c:1:6: note: at offset 0 to object âaâ with size 6 declared here 1 | char a[2][3]; | ^ maybe_invalidate called for a[_2][0] = 0; maybe_invalidate returns 0 Pass statistics of "strlen": ---------------- f (unsigned intD.9 iD.1931) { unsigned intD.9 i_1(D) = iD.1931; unsigned intD.9 _2; ;; basic block 2, loop depth 0, count 1073741824 (estimated locally), maybe hot ;; prev block 0, next block 1, flags: (NEW, REACHABLE, VISITED) ;; pred: ENTRY [always] count:1073741824 (estimated locally) (FALLTHRU,EXECUTABLE) # RANGE [0, 4294967294] _2 = MIN_EXPR <i_1(D), 4294967294>; # .MEM_4 = VDEF <.MEM_3(D)> aD.1930[_2][0] = 0; # VUSE <.MEM_4> return; ;; succ: EXIT [always] count:1073741824 (estimated locally) (EXECUTABLE) }