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wcc: loop-label stack guards its depth loudly, both stages

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wwstage's unguarded loop-label push wrote out of bounds at depth 17
(compiler-heap corruption); cstage guarded but emitted a wrong break
target. Loud cap error at the limit, both stages, agreeing wording.
This commit is contained in:
Hojun-Cho
2026-06-13 04:34:36 +09:00
parent 92cd573197
commit f7845057a7
6 changed files with 244 additions and 10 deletions
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24
cmd/w6c/cgen.c
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@@ -14282,11 +14282,13 @@ cgstmt(Cg *c, Node *n, Local **locals, int *frame)
* continue. Dedicated `rpost` label; bootstrap-NEUTRAL (no
* range-form continue callers in lib/ or selfhost/). */
char *rpost = mklabel(c, "rpost");
if (nloops < LOOP_MAX) {
loop_cont[nloops] = rpost;
loop_brk[nloops] = end;
nloops++;
}
/* #42: at the cap, fail loud rather than silently push a wrong
* break/continue target (the ww twin in cgenstmt.ww guards too). */
if (nloops >= LOOP_MAX)
fatal("cgen: loop nesting too deep");
loop_cont[nloops] = rpost;
loop_brk[nloops] = end;
nloops++;
label(c, loop);
ins2(c, A_MOVQ, amem(D_BP, ioff), areg(D_AX));
ins2(c, A_MOVQ, amem(D_BP, loff), areg(D_BX));
@@ -14430,11 +14432,13 @@ cgstmt(Cg *c, Node *n, Local **locals, int *frame)
ins2(c, A_CMPQ, aimm(0), areg(D_AX));
ins1(c, A_JE, abranch(natural_exit));
}
if (nloops < LOOP_MAX) {
loop_cont[nloops] = cont_target;
loop_brk[nloops] = end;
nloops++;
}
/* #42: at the cap, fail loud rather than silently push a wrong
* break/continue target (the ww twin in cgenstmt.ww guards too). */
if (nloops >= LOOP_MAX)
fatal("cgen: loop nesting too deep");
loop_cont[nloops] = cont_target;
loop_brk[nloops] = end;
nloops++;
cgstmt(c, n->body, locals, frame);
if (nloops > 0) nloops--;
if (n->rhs) {