cgen: str chained-*struct field read -> 3-word -- Phase 2 C4.6 caseB (both stages)
The chained N_DOT path (o.p.f, depth>=2, base AX) still loaded a str-typed field as 2 words, dropping cap -- the C4.6 sibling deferred to caseB. Fold the str case onto the adjacent 3-word slice-field arm (widen kind-gate: cstage type_isstr, ww typeisstr; never size==24). Emits len->BX+8, cap->CX+16, ptr->AX+0 LAST (AX is the base). cstage==wwstage byte-identical; the slice arm is unchanged for slices. test/wcc/934: table-driven runtime .cap-survives over the chained read; the row interposes a CX-clobbering call so a 2-word read cannot coincidentally pass on stale CX (per the 933 discriminator lesson). Verified fail-before/pass-after on both drivers. main.combined.ww regenerated via the canonical make path (md5-stable).
This commit is contained in:
7
Makefile
7
Makefile
@@ -256,6 +256,7 @@ TESTS = $(BIN)/test_smoke $(BIN)/test_lex $(BIN)/test_parse $(BIN)/test_check \
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$(BIN)/test_str_abi_run \
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$(BIN)/test_str_elem_cap_run \
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$(BIN)/test_str_field_cap_run \
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$(BIN)/test_str_chained_field_cap_run \
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$(BIN)/test_composite_call_arg \
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$(BIN)/test_composite_call_arg_run \
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$(BIN)/test_letdecl_zeroinit \
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@@ -634,6 +635,12 @@ $(BIN)/test_str_field_cap_run: test/wcc/933_str_field_cap_run.c \
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$(LIB)/libwwrt.a | $(BIN)
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$(CC) $(CFLAGS) -o $@ $<
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$(BIN)/test_str_chained_field_cap_run: test/wcc/934_str_chained_field_cap_run.c \
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$(BIN)/ww $(BIN)/w6c $(BIN)/w6a $(BIN)/w6l \
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$(BIN)/ww_ww $(BIN)/w6c_ww $(BIN)/w6a_ww $(BIN)/w6l_ww \
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$(LIB)/libwwrt.a | $(BIN)
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$(CC) $(CFLAGS) -o $@ $<
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$(BIN)/test_composite_call_arg: test/wcc/723_composite_call_arg.c \
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$(BIN)/w6c $(BIN)/w6c_ww | $(BIN)
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$(CC) $(CFLAGS) -o $@ $<
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@@ -6061,20 +6061,13 @@ cgexpr(Cg *c, Node *n, Local *locals)
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Type *ft = f->type;
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Type *fu = (ft && ft->kind == TY_NAMED)
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? ft->under : ft;
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/* str field: load (ptr, len) into (AX, BX). */
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if (fu && fu->kind == TY_STR) {
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ins2(c, A_MOVQ,
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amem(D_AX, (int)f->offset + 8),
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areg(D_BX));
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ins2(c, A_MOVQ,
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amem(D_AX, (int)f->offset + 0),
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areg(D_AX));
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goto dot_done;
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}
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/* slice field: load (ptr, len, cap) into
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/* str IS []u8 — same 3-word {ptr,len,cap} as a
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* slice field: load (ptr, len, cap) into
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* (AX, BX, CX). AX is the *struct base, so
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* load .ptr (which targets AX) LAST. */
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if (fu && fu->kind == TY_SLICE) {
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* load .ptr (which targets AX) LAST. str folds
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* onto the slice arm (#1/Phase 3 collapse). */
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if ((fu && fu->kind == TY_SLICE) ||
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type_isstr(ft)) {
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ins2(c, A_MOVQ,
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amem(D_AX, (int)f->offset + 8),
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areg(D_BX));
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@@ -15928,21 +15928,14 @@ fn cgdot(c: *cgen, n: *node) void = {
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if (streq(tf.name, fld)) {
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let ft: *tinfo = tf.type_;
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cgexpr(c, lhs); // AX = ptr to inner struct
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// str field: load both halves.
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if (typeisstr(ft)) {
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emitline("\tMOVQ\t");
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emitdispreg((tf.offset + 8u64): i64, "AX");
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emitline(", BX\n");
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emitline("\tMOVQ\t");
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emitdispreg(tf.offset: i64, "AX");
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emitline(", AX\n");
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return;
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};
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// slice field: load (ptr, len, cap)
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// str IS []u8 — same 3-word {ptr,len,cap}
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// as a slice field: load (ptr, len, cap)
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// into (AX, BX, CX). AX is the *struct
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// base, so load .ptr (which targets
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// AX) LAST.
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if (typeisslice(ft)) {
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// AX) LAST. str folds onto the slice
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// arm (#1/Phase 3 collapse; cite cstage
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// cgen.c N_DOT chained *struct caseB).
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if (typeisstr(ft) || typeisslice(ft)) {
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emitline("\tMOVQ\t");
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emitdispreg((tf.offset + 8u64): i64, "AX");
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emitline(", BX\n");
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@@ -2100,21 +2100,14 @@ fn cgdot(c: *cgen, n: *node) void = {
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if (streq(tf.name, fld)) {
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let ft: *tinfo = tf.type_;
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cgexpr(c, lhs); // AX = ptr to inner struct
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// str field: load both halves.
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if (typeisstr(ft)) {
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emitline("\tMOVQ\t");
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emitdispreg((tf.offset + 8u64): i64, "AX");
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emitline(", BX\n");
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emitline("\tMOVQ\t");
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emitdispreg(tf.offset: i64, "AX");
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emitline(", AX\n");
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return;
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};
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// slice field: load (ptr, len, cap)
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// str IS []u8 — same 3-word {ptr,len,cap}
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// as a slice field: load (ptr, len, cap)
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// into (AX, BX, CX). AX is the *struct
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// base, so load .ptr (which targets
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// AX) LAST.
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if (typeisslice(ft)) {
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// AX) LAST. str folds onto the slice
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// arm (#1/Phase 3 collapse; cite cstage
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// cgen.c N_DOT chained *struct caseB).
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if (typeisstr(ft) || typeisslice(ft)) {
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emitline("\tMOVQ\t");
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emitdispreg((tf.offset + 8u64): i64, "AX");
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emitline(", BX\n");
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@@ -15928,21 +15928,14 @@ fn cgdot(c: *cgen, n: *node) void = {
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if (streq(tf.name, fld)) {
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let ft: *tinfo = tf.type_;
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cgexpr(c, lhs); // AX = ptr to inner struct
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// str field: load both halves.
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if (typeisstr(ft)) {
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emitline("\tMOVQ\t");
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emitdispreg((tf.offset + 8u64): i64, "AX");
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emitline(", BX\n");
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emitline("\tMOVQ\t");
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emitdispreg(tf.offset: i64, "AX");
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emitline(", AX\n");
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return;
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};
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// slice field: load (ptr, len, cap)
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// str IS []u8 — same 3-word {ptr,len,cap}
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// as a slice field: load (ptr, len, cap)
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// into (AX, BX, CX). AX is the *struct
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// base, so load .ptr (which targets
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// AX) LAST.
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if (typeisslice(ft)) {
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// AX) LAST. str folds onto the slice
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// arm (#1/Phase 3 collapse; cite cstage
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// cgen.c N_DOT chained *struct caseB).
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if (typeisstr(ft) || typeisslice(ft)) {
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emitline("\tMOVQ\t");
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emitdispreg((tf.offset + 8u64): i64, "AX");
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emitline(", BX\n");
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168
test/wcc/934_str_chained_field_cap_run.c
Normal file
168
test/wcc/934_str_chained_field_cap_run.c
Normal file
@@ -0,0 +1,168 @@
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/*
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* 934_str_chained_field_cap_run — runtime coverage for the C4.6-caseB fold:
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* a CHAINED str-field read `o.p.f` (depth >= 2, where p is a *struct field of
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* o and f is a str field of *p) must load the full 24B {ptr,len,cap} header,
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* not just {ptr,len}. str is 24B since Phase 2 (#1); pre-caseB the chained
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* *struct N_DOT str arm loaded 2 words (ptr in AX, len in BX) and dropped cap.
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*
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* This is the chained sibling of 933 (which covered the direct / single-deref
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* S1/S2 arms). The site is cgen.c's "Chained N_DOT through a *struct field"
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* branch (n->lhs is itself an N_DOT typed *struct): the lhs cgexpr leaves AX =
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* the inner *struct pointer, then the field is read off AX. caseB folds the
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* str arm onto the adjacent 3-word slice arm — cap loads from +16(AX) and the
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* base (AX = ptr) is read LAST so the earlier index loads still see the base.
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*
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* The byte-id gates (990-997) can't catch a symmetric 2-word miscompile: if
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* both stages drop cap identically, byte-id passes silently. So this pins the
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* *runtime* contract — build through both the cstage `ww` and wwstage `ww_ww`
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* driver and confirm the assertion holds (exit 0).
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*
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* DISCRIMINATION (heed the 933 lesson): a 2-word read leaves CX untouched, so
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* the row could coincidentally pass if CX happened to still carry the poison
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* cap. spoil() interposes a call between the field store and the chained read;
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* a call clobbers caller-saved CX (spoil's own str copy leaves cap=44 in CX),
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* so a broken 2-word read observes cap=44, not 8, and the row fails (return 1).
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* Verified fail-before (reverted fold: exit 1) / pass-after (exit 0), both
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* drivers.
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*/
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include <unistd.h>
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#include <sys/stat.h>
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#include <sys/wait.h>
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static int
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runwait(const char *cmd)
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{
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int rc = system(cmd);
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if (rc == -1) return -1;
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if (WIFEXITED(rc)) return WEXITSTATUS(rc);
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return -1;
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}
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struct row { const char *label; const char *src; int want; };
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static const struct row rows[] = {
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/* caseB — `o.p.f` chained read: o a struct holding p: *inr, inr
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* holding a str field f. Base AX = the inner *struct pointer; the
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* str field is read 3-word off AX (cap at +16). Poison cap=8
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* (len=2). spoil() interposes a CX-clobbering call between the
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* `ist.f = p` store and the chained `o.p.f` read so a broken
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* 2-word read cannot coincidentally pass on a stale CX. */
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{ "caseb_chained_field",
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"type inr = struct { f: str };\n"
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"type otr = struct { p: *inr };\n"
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"fn spoil() i32 = {\n"
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" let z: str = \"zzzz\";\n"
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" z.cap = 44i32;\n"
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" let w: str = z;\n"
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" return w.cap: i32;\n"
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"};\n"
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"export fn main() i32 = {\n"
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" let p: str = \"hi\";\n"
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" p.cap = 8i32;\n"
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" let ist: inr;\n"
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" ist.f = p;\n"
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" let o: otr;\n"
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" o.p = &ist;\n"
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" let junk: i32 = spoil();\n"
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" let s: str = o.p.f;\n"
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" if (s.cap: i32 != 8) { return 1; };\n"
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" if (s.len: i32 != 2) { return 2; };\n"
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" if (junk != 44) { return 3; };\n"
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" return 0;\n"
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"};\n",
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0 },
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};
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static int
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run_driver(const char *driver, const struct row *r, int i)
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{
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char src[96], tmpdir[96], cmd[1024];
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snprintf(src, sizeof src, "/tmp/strchainfieldcap_%d_%d.ww", getpid(), i);
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snprintf(tmpdir, sizeof tmpdir, "/tmp/strchainfieldcap_%d_d_%d", getpid(), i);
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FILE *f = fopen(src, "wb");
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if (!f) return -1;
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fputs(r->src, f);
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fclose(f);
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mkdir(tmpdir, 0755);
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snprintf(cmd, sizeof cmd, "cd %s && %s build %s",
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tmpdir, driver, src);
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if (runwait(cmd) != 0) {
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fprintf(stderr, "row[%s]: build via %s failed\n",
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r->label, driver);
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unlink(src); rmdir(tmpdir);
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return -1;
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}
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const char *base = strrchr(src, '/');
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base = base ? base + 1 : src;
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char outbin[160];
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snprintf(outbin, sizeof outbin, "%s/%s", tmpdir, base);
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char *dot = strrchr(outbin, '.');
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if (dot && strcmp(dot, ".ww") == 0) *dot = '\0';
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int got = runwait(outbin);
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unlink(src); unlink(outbin); rmdir(tmpdir);
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return got;
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}
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int
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main(void)
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{
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const char *bin = getenv("BIN");
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if (!bin) bin = "out/bin";
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char absbin[512];
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if (bin[0] != '/') {
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char cwd[256];
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if (getcwd(cwd, sizeof cwd) == NULL) return 1;
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snprintf(absbin, sizeof absbin, "%s/%s", cwd, bin);
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bin = absbin;
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}
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char cdrv[640];
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snprintf(cdrv, sizeof cdrv, "%s/ww", bin);
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char wdrv[640];
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snprintf(wdrv, sizeof wdrv, "%s/ww_ww", bin);
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struct { const char *name; const char *path; int gated_on_existence; }
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drivers[] = {
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{ "cstage", cdrv, 0 },
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{ "wwstage", wdrv, 1 },
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{ NULL, NULL, 0 },
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};
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int n = (int)(sizeof rows / sizeof rows[0]);
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int total = 0, fail = 0;
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for (int d = 0; drivers[d].name; d++) {
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if (drivers[d].gated_on_existence
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&& access(drivers[d].path, X_OK) != 0) {
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fprintf(stderr,
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"str_chained_field_cap_run: skip %s (no %s)\n",
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drivers[d].name, drivers[d].path);
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continue;
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}
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for (int i = 0; i < n; i++) {
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int got = run_driver(drivers[d].path, &rows[i], i);
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total++;
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if (got != rows[i].want) {
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fprintf(stderr,
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"str_chained_field_cap_run[%s][%s]: exit=%d want=%d\n",
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drivers[d].name, rows[i].label,
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got, rows[i].want);
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fail++;
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}
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}
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}
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if (fail) {
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fprintf(stderr, "str_chained_field_cap_run: %d/%d fixtures failed\n",
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fail, total);
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return 1;
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}
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printf("str_chained_field_cap_run: %d/%d ok\n", total, total);
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return 0;
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}
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