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w6c+wwstage: source sub-8 value-struct ABI-size from tinfo.size at zero-init+DATAW (#254)

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wwstage conflated SLOT-size (round-to-8, for frame) with ABI-size (true)
for a nested value-struct. A nested value-struct field is sized via
fieldsize() (TY_STRUCT -> ti.slotsize = 8), poisoning structabisize and
registerstruct si.totsize to 8 for a struct whose true ABI size is 4.
Two emission sites then over-sized, both SILENT cs!=ww divergences:

  D1 (local, cgenstmt.ww cglet): zsz = structabisize = 8 hit the
     `zsz == 8` zero arm (#213) -> a stray `MOVQ $0, off(BP)` cstage
     never emits (ABI 4 is sub-8 -> left uninit per the shared no-rhs
     zero-init policy).
  D2 (global, cgen.ww emitletdataw): the struct zero arm wrote
     letemitsize/si.totsize = 8 DATAW bytes; cstage cg_let_emit_size
     returns u->size = 4.

Fix sources the zero-init extent from the type table's tinfo.size
(peeling TY_NAMED) at both sites — the same value cstage reads
(cgen.c:8397 / :978). fieldsize / registerstruct / frame slot-padding
stay UNTOUCHED: moving the fix into the size helpers would shift
nested-struct field offsets and re-diverge other byte-id. Pure
wwstage-align-down; cstage cmd/w6c/cgen.c unchanged.

Test 949_valstruct_subsize_run: D1 local + D2 global over ABI sizes
1/2/4 (the whole sub-8 / non-8-multiple class), each cstage-run +
cs==ww .s byte-id; plus a >8 (16B) local+global NEGATIVE control
proving the fix didn't disable legitimate multi-word zero-init.

Regen w6c + wwdump main.combined.ww (cgen is compiler-imported, #110).
This commit is contained in:
Hojun-Cho
2026-06-02 05:37:47 +09:00
parent e92708ecda
commit be23d7227a
6 changed files with 369 additions and 24 deletions
Download Patch File Download Diff File Expand all files Collapse all files

6
Makefile
View File

@@ -405,6 +405,7 @@ TESTS = $(BIN)/test_smoke $(BIN)/test_lex $(BIN)/test_parse $(BIN)/test_check \
$(BIN)/test_dotbase_addr_slice_run \
$(BIN)/test_structlit_arrfield_run \
$(BIN)/test_arraytoslice_run \
$(BIN)/test_valstruct_subsize_run \
$(BIN)/test_continue_run \
$(BIN)/test_callret_unsigned_arith_run \
$(BIN)/test_sar_shr_run \
@@ -1611,6 +1612,11 @@ $(BIN)/test_arraytoslice_run: test/wcc/953_arraytoslice_run.c \
$(LIB)/libwwrt.a | $(BIN)
$(CC) $(CFLAGS) -o $@ $<
$(BIN)/test_valstruct_subsize_run: test/wcc/949_valstruct_subsize_run.c \
$(BIN)/ww $(BIN)/w6c $(BIN)/w6c_ww $(BIN)/w6a $(BIN)/w6l \
$(LIB)/libwwrt.a | $(BIN)
$(CC) $(CFLAGS) -o $@ $<
$(BIN)/test_continue_run: test/wcc/911_continue_run.c $(BIN)/ww \
$(BIN)/w6c $(BIN)/w6c_ww $(BIN)/w6a $(BIN)/w6l \
$(LIB)/libwwrt.a | $(BIN)

44
selfhost/cmd/w6c/main.combined.ww
View File

@@ -28899,17 +28899,29 @@ fn cglet(c: *cgen, n: *node) void = {
if (n.lhs.kind == nkind.N_TARRAY) { isarr = true; };
};
// Zero-fill extent. cstage sizes the run on `lu->size`
// (the maxalign-rounded ABI size, check.c:760); wwstage's
// `sz` from letslotsize is slot-padded (round-to-8), so a
// struct with maxalign<8 and a sub-8 tail would over-zero
// MOVQ where cstage emits MOVL/MOVB. Read structabisize
// for a struct-typed let to converge; slot allocation
// stays on `sz` (frame uses slot-padded slots).
// (the natural ABI size from the type table, cgen.c:8397);
// wwstage's `sz` from letslotsize is slot-padded (round-to-8),
// so a struct with maxalign<8 and a sub-8 tail would over-zero
// MOVQ where cstage emits nothing. Source the extent from the
// type table's tinfo.size for a struct-typed let to converge;
// slot allocation stays on `sz` (frame uses slot-padded slots).
// #254: structabisize is NOT a sound ABI-size source here — it
// sums fieldsize(), which slot-pads a nested value-struct field
// to 8, so a sub-8 outer struct (e.g. `struct{struct{[4]u8}}`,
// ABI 4) read 8 and emitted a stray MOVQ $0 cstage doesn't.
// fieldsize / registerstruct / frame slot-padding stay
// UNTOUCHED — moving the fix there would shift field offsets.
let zsz: i32 = sz;
if (n.lhs != nil) {
if (n.lhs.kind == nkind.N_TNAME) {
let szi: *structinfo = structlookupchain(c, n.lhs);
if (szi != nil) { zsz = structabisize(szi); };
if (szi != nil) {
let ti: *tinfo = n.lhs.type_: *tinfo;
for (ti != nil && ti.kind == tykind.TY_NAMED) {
ti = ti.under;
};
if (ti != nil) { zsz = ti.size: i32; };
};
};
};
if (typeis8byteprimitive(c, n.lhs)) {
@@ -32324,13 +32336,29 @@ fn emitletdataw(c: *cgen, file: *node) void = {
// A struct literal init isn't compile-time
// evaluated yet; skip and the link will surface
// an undefined-symbol error if referenced.
// #254: the zero-fill byte count comes from the
// type table's tinfo.size (cstage cg_let_emit_size
// returns u->size, cgen.c:978), NOT letemitsize/
// si.totsize — registerstruct rounds the nested
// value-struct field's slot to 8, so a sub-8 outer
// struct (ABI 4) over-emitted DATAW 8 bytes vs
// cstage's 4. registerstruct / fieldsize / frame
// slot-padding stay UNTOUCHED (field offsets).
if (issg) {
if (d.rhs == nil) {
let zsz: i32 = sz;
if (d.lhs != nil) {
let ti: *tinfo = d.lhs.type_: *tinfo;
for (ti != nil && ti.kind == tykind.TY_NAMED) {
ti = ti.under;
};
if (ti != nil) { zsz = ti.size: i32; };
};
emitline("DATAW ");
emitsymnamehint(c, nm, d.nmod);
emitline("(SB),\"");
let i: i32 = 0;
for (i < sz) {
for (i < zsz) {
emitdatawbyte(0u8);
i += 1;
};

18
selfhost/cmd/wcc/cgen.ww
View File

@@ -1990,13 +1990,29 @@ fn emitletdataw(c: *cgen, file: *node) void = {
// A struct literal init isn't compile-time
// evaluated yet; skip and the link will surface
// an undefined-symbol error if referenced.
// #254: the zero-fill byte count comes from the
// type table's tinfo.size (cstage cg_let_emit_size
// returns u->size, cgen.c:978), NOT letemitsize/
// si.totsize — registerstruct rounds the nested
// value-struct field's slot to 8, so a sub-8 outer
// struct (ABI 4) over-emitted DATAW 8 bytes vs
// cstage's 4. registerstruct / fieldsize / frame
// slot-padding stay UNTOUCHED (field offsets).
if (issg) {
if (d.rhs == nil) {
let zsz: i32 = sz;
if (d.lhs != nil) {
let ti: *tinfo = d.lhs.type_: *tinfo;
for (ti != nil && ti.kind == tykind.TY_NAMED) {
ti = ti.under;
};
if (ti != nil) { zsz = ti.size: i32; };
};
emitline("DATAW ");
emitsymnamehint(c, nm, d.nmod);
emitline("(SB),\"");
let i: i32 = 0;
for (i < sz) {
for (i < zsz) {
emitdatawbyte(0u8);
i += 1;
};

26
selfhost/cmd/wcc/cgenstmt.ww
View File

@@ -1768,17 +1768,29 @@ fn cglet(c: *cgen, n: *node) void = {
if (n.lhs.kind == nkind.N_TARRAY) { isarr = true; };
};
// Zero-fill extent. cstage sizes the run on `lu->size`
// (the maxalign-rounded ABI size, check.c:760); wwstage's
// `sz` from letslotsize is slot-padded (round-to-8), so a
// struct with maxalign<8 and a sub-8 tail would over-zero
// MOVQ where cstage emits MOVL/MOVB. Read structabisize
// for a struct-typed let to converge; slot allocation
// stays on `sz` (frame uses slot-padded slots).
// (the natural ABI size from the type table, cgen.c:8397);
// wwstage's `sz` from letslotsize is slot-padded (round-to-8),
// so a struct with maxalign<8 and a sub-8 tail would over-zero
// MOVQ where cstage emits nothing. Source the extent from the
// type table's tinfo.size for a struct-typed let to converge;
// slot allocation stays on `sz` (frame uses slot-padded slots).
// #254: structabisize is NOT a sound ABI-size source here — it
// sums fieldsize(), which slot-pads a nested value-struct field
// to 8, so a sub-8 outer struct (e.g. `struct{struct{[4]u8}}`,
// ABI 4) read 8 and emitted a stray MOVQ $0 cstage doesn't.
// fieldsize / registerstruct / frame slot-padding stay
// UNTOUCHED — moving the fix there would shift field offsets.
let zsz: i32 = sz;
if (n.lhs != nil) {
if (n.lhs.kind == nkind.N_TNAME) {
let szi: *structinfo = structlookupchain(c, n.lhs);
if (szi != nil) { zsz = structabisize(szi); };
if (szi != nil) {
let ti: *tinfo = n.lhs.type_: *tinfo;
for (ti != nil && ti.kind == tykind.TY_NAMED) {
ti = ti.under;
};
if (ti != nil) { zsz = ti.size: i32; };
};
};
};
if (typeis8byteprimitive(c, n.lhs)) {

44
selfhost/cmd/wwdump/main.combined.ww
View File

@@ -28899,17 +28899,29 @@ fn cglet(c: *cgen, n: *node) void = {
if (n.lhs.kind == nkind.N_TARRAY) { isarr = true; };
};
// Zero-fill extent. cstage sizes the run on `lu->size`
// (the maxalign-rounded ABI size, check.c:760); wwstage's
// `sz` from letslotsize is slot-padded (round-to-8), so a
// struct with maxalign<8 and a sub-8 tail would over-zero
// MOVQ where cstage emits MOVL/MOVB. Read structabisize
// for a struct-typed let to converge; slot allocation
// stays on `sz` (frame uses slot-padded slots).
// (the natural ABI size from the type table, cgen.c:8397);
// wwstage's `sz` from letslotsize is slot-padded (round-to-8),
// so a struct with maxalign<8 and a sub-8 tail would over-zero
// MOVQ where cstage emits nothing. Source the extent from the
// type table's tinfo.size for a struct-typed let to converge;
// slot allocation stays on `sz` (frame uses slot-padded slots).
// #254: structabisize is NOT a sound ABI-size source here — it
// sums fieldsize(), which slot-pads a nested value-struct field
// to 8, so a sub-8 outer struct (e.g. `struct{struct{[4]u8}}`,
// ABI 4) read 8 and emitted a stray MOVQ $0 cstage doesn't.
// fieldsize / registerstruct / frame slot-padding stay
// UNTOUCHED — moving the fix there would shift field offsets.
let zsz: i32 = sz;
if (n.lhs != nil) {
if (n.lhs.kind == nkind.N_TNAME) {
let szi: *structinfo = structlookupchain(c, n.lhs);
if (szi != nil) { zsz = structabisize(szi); };
if (szi != nil) {
let ti: *tinfo = n.lhs.type_: *tinfo;
for (ti != nil && ti.kind == tykind.TY_NAMED) {
ti = ti.under;
};
if (ti != nil) { zsz = ti.size: i32; };
};
};
};
if (typeis8byteprimitive(c, n.lhs)) {
@@ -32324,13 +32336,29 @@ fn emitletdataw(c: *cgen, file: *node) void = {
// A struct literal init isn't compile-time
// evaluated yet; skip and the link will surface
// an undefined-symbol error if referenced.
// #254: the zero-fill byte count comes from the
// type table's tinfo.size (cstage cg_let_emit_size
// returns u->size, cgen.c:978), NOT letemitsize/
// si.totsize — registerstruct rounds the nested
// value-struct field's slot to 8, so a sub-8 outer
// struct (ABI 4) over-emitted DATAW 8 bytes vs
// cstage's 4. registerstruct / fieldsize / frame
// slot-padding stay UNTOUCHED (field offsets).
if (issg) {
if (d.rhs == nil) {
let zsz: i32 = sz;
if (d.lhs != nil) {
let ti: *tinfo = d.lhs.type_: *tinfo;
for (ti != nil && ti.kind == tykind.TY_NAMED) {
ti = ti.under;
};
if (ti != nil) { zsz = ti.size: i32; };
};
emitline("DATAW ");
emitsymnamehint(c, nm, d.nmod);
emitline("(SB),\"");
let i: i32 = 0;
for (i < sz) {
for (i < zsz) {
emitdatawbyte(0u8);
i += 1;
};

255
test/wcc/949_valstruct_subsize_run.c Normal file
View File

@@ -0,0 +1,255 @@
/*
* 949_valstruct_subsize_run — runtime + byte-id net for #254: a sub-8
* (non-8-multiple) nested value-struct must size its zero-init extent
* from the type table's natural ABI size (cstage lu->size), NOT the
* slot-padded register-struct width.
*
* Root: wwstage conflated SLOT-size (round-to-8, for frame layout) with
* ABI-size (true). A nested value-struct field was sized via fieldsize()
* (cgenutil.ww TY_STRUCT -> ti.slotsize = 8), poisoning structabisize +
* registerstruct si.totsize to 8 for a struct whose true ABI size is 4.
* Two emission sites then over-sized:
* D1 (local): cglet zsz = structabisize = 8 hit the `zsz == 8` zero
* arm (cgenstmt.ww #213) -> a stray `MOVQ $0, off(BP)` that cstage
* (ABI 4 is sub-8 -> left uninit per the shared no-rhs policy)
* never emits.
* D2 (global): emitletdataw struct arm wrote si.totsize = 8 zero bytes
* of DATAW; cstage cg_let_emit_size returns u->size = 4.
* Both were SILENT cs!=ww divergences (gate-blind: a standalone wwstage
* is self-consistent; only the cs==ww .s cmp catches it).
*
* Fix (rule-13 SSoT): both sites source the extent from tinfo.size
* (peeling TY_NAMED), the same value cstage reads. fieldsize /
* registerstruct / frame slot-padding stay UNTOUCHED — moving the fix
* into the size helpers would shift nested-struct field offsets and
* re-diverge other byte-id.
*
* Rows cover the whole sub-8 class (ABI size 1/2/4) in both the local
* (D1) and global (D2) emission contexts, plus a >8 NEGATIVE control
* proving the fix didn't disable legitimate multi-word zero-init. Each
* row: cstage `ww build` + run for the exit code (correctness) AND
* w6c vs w6c_ww `.s` cmp for rule-10 byte-id (the silent-divergence net).
*/
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/stat.h>
#include <sys/wait.h>
static int
runwait(const char *cmd)
{
int rc = system(cmd);
if (rc == -1) return -1;
if (WIFEXITED(rc)) return WEXITSTATUS(rc);
return -1;
}
struct row { const char *label; const char *src; int want_exit; };
static const struct row rows[] = {
/* D1 local, ABI size 4 (inner {[4]u8}). Pre-fix wwstage emitted a
* stray MOVQ $0 cstage didn't -> .s differ. Write+read a byte so
* the exit is deterministic (sub-8 is left uninit by BOTH stages,
* matching cstage's no-rhs policy). */
{ "d1_local_4",
"package main;\n"
"type inner = struct { m: [4]u8 };\n"
"type outv = struct { i: inner };\n"
"export fn main() i32 = {\n"
" let o: outv;\n"
" o.i.m[0] = 66u8;\n"
" return o.i.m[0]: i32;\n"
"};\n", 66 },
/* D1 local, ABI size 2 ([2]u8). */
{ "d1_local_2",
"package main;\n"
"type inner = struct { m: [2]u8 };\n"
"type outv = struct { i: inner };\n"
"export fn main() i32 = {\n"
" let o: outv;\n"
" o.i.m[1] = 55u8;\n"
" return o.i.m[1]: i32;\n"
"};\n", 55 },
/* D1 local, ABI size 1 ([1]u8) — the tightest sub-8 case. */
{ "d1_local_1",
"package main;\n"
"type inner = struct { m: [1]u8 };\n"
"type outv = struct { i: inner };\n"
"export fn main() i32 = {\n"
" let o: outv;\n"
" o.i.m[0] = 44u8;\n"
" return o.i.m[0]: i32;\n"
"};\n", 44 },
/* D2 global, ABI size 4. Pre-fix wwstage emitted DATAW of 8 zero
* bytes vs cstage's 4 -> .s differ. */
{ "d2_global_4",
"package main;\n"
"type inner = struct { m: [4]u8 };\n"
"type outv = struct { i: inner };\n"
"let g: outv;\n"
"export fn main() i32 = {\n"
" g.i.m[0] = 66u8;\n"
" return g.i.m[0]: i32;\n"
"};\n", 66 },
/* D2 global, ABI size 2. */
{ "d2_global_2",
"package main;\n"
"type inner = struct { m: [2]u8 };\n"
"type outv = struct { i: inner };\n"
"let g: outv;\n"
"export fn main() i32 = {\n"
" g.i.m[1] = 55u8;\n"
" return g.i.m[1]: i32;\n"
"};\n", 55 },
/* D2 global, ABI size 1. */
{ "d2_global_1",
"package main;\n"
"type inner = struct { m: [1]u8 };\n"
"type outv = struct { i: inner };\n"
"let g: outv;\n"
"export fn main() i32 = {\n"
" g.i.m[0] = 44u8;\n"
" return g.i.m[0]: i32;\n"
"};\n", 44 },
/* NEGATIVE control — a >8 (multi-word) value-struct still zero-
* inits. Read an UNWRITTEN byte: a working multi-word zero-init
* fill makes it 0. If the fix had wrongly suppressed the >8 zero
* arm, this would read stack garbage (and byte-id would diff
* against the still-zeroing cstage). Local + global both proven. */
{ "ctl_local_16",
"package main;\n"
"type inner = struct { m: [16]u8 };\n"
"type outv = struct { i: inner };\n"
"export fn main() i32 = {\n"
" let o: outv;\n"
" return o.i.m[7]: i32;\n"
"};\n", 0 },
{ "ctl_global_16",
"package main;\n"
"type inner = struct { m: [16]u8 };\n"
"type outv = struct { i: inner };\n"
"let g: outv;\n"
"export fn main() i32 = {\n"
" return g.i.m[7]: i32;\n"
"};\n", 0 },
{ NULL, NULL, 0 }
};
static int
slurp_eq(const char *a, const char *b)
{
FILE *fa = fopen(a, "rb");
FILE *fb = fopen(b, "rb");
if (!fa || !fb) { if (fa) fclose(fa); if (fb) fclose(fb); return -1; }
int rc = 0;
for (;;) {
int ca = fgetc(fa);
int cb = fgetc(fb);
if (ca != cb) { rc = -1; break; }
if (ca == EOF) break;
}
fclose(fa); fclose(fb);
return rc;
}
int
main(void)
{
const char *bin = getenv("BIN");
if (!bin) bin = "out/bin";
char absbin[1024];
if (bin[0] != '/') {
char cwd[1024];
if (getcwd(cwd, sizeof cwd) == NULL) return 1;
snprintf(absbin, sizeof absbin, "%s/%s", cwd, bin);
bin = absbin;
}
char w6c[1100], w6c_ww[1100];
snprintf(w6c, sizeof w6c, "%s/w6c", bin);
snprintf(w6c_ww, sizeof w6c_ww, "%s/w6c_ww", bin);
if (access(w6c_ww, X_OK) != 0) {
fprintf(stderr, "valstruct_subsize: w6c_ww missing — cannot run "
"the cs==ww byte-id gate (the whole point of this test)\n");
return 1;
}
int n = 0, fail = 0;
for (int i = 0; rows[i].src; i++, n++) {
char src[64];
snprintf(src, sizeof src, "/tmp/wwvss_%d_%d.ww", getpid(), i);
FILE *f = fopen(src, "wb");
if (f == NULL) { fail++; continue; }
fputs(rows[i].src, f);
fclose(f);
char tmpdir[64];
snprintf(tmpdir, sizeof tmpdir, "/tmp/wwvss_%d_d_%d",
getpid(), i);
mkdir(tmpdir, 0755);
char cmd[2048];
snprintf(cmd, sizeof cmd, "cd %s && %s/ww build %s",
tmpdir, bin, src);
if (runwait(cmd) != 0) {
fprintf(stderr, "row[%s]: cstage build failed\n",
rows[i].label);
fail++;
unlink(src); rmdir(tmpdir);
continue;
}
char outbin[128];
const char *base = strrchr(src, '/');
base = base ? base + 1 : src;
snprintf(outbin, sizeof outbin, "%s/%s", tmpdir, base);
char *dot = strrchr(outbin, '.');
if (dot && strcmp(dot, ".ww") == 0) *dot = '\0';
int got = runwait(outbin);
if (got != rows[i].want_exit) {
fprintf(stderr, "row[%s]: cstage exit %d, want %d\n",
rows[i].label, got, rows[i].want_exit);
fail++;
}
unlink(outbin); rmdir(tmpdir);
char cs_s[64], ws_s[64];
snprintf(cs_s, sizeof cs_s, "/tmp/wwvss_%d_%d_cs.s",
getpid(), i);
snprintf(ws_s, sizeof ws_s, "/tmp/wwvss_%d_%d_ww.s",
getpid(), i);
snprintf(cmd, sizeof cmd, "%s -o %s %s 2>/dev/null",
w6c, cs_s, src);
if (runwait(cmd) != 0) {
fprintf(stderr, "row[%s]: w6c failed\n", rows[i].label);
fail++; unlink(src); continue;
}
snprintf(cmd, sizeof cmd, "%s -o %s %s 2>/dev/null",
w6c_ww, ws_s, src);
if (runwait(cmd) != 0) {
fprintf(stderr, "row[%s]: w6c_ww failed\n",
rows[i].label);
fail++; unlink(src); unlink(cs_s); continue;
}
if (slurp_eq(cs_s, ws_s) != 0) {
fprintf(stderr,
"row[%s]: cstage/wwstage .s DIFFER (rule-10 "
"byte-id violation)\n", rows[i].label);
fail++;
}
unlink(src); unlink(cs_s); unlink(ws_s);
}
if (fail) {
fprintf(stderr, "%d/%d valstruct-subsize tests failed\n",
fail, n);
return 1;
}
printf("valstruct_subsize: %d/%d ok (cstage run + cs==ww byte-id)\n",
n, n);
return 0;
}