Commit 1d6eb2e9 authored by Rémy Oudompheng's avatar Rémy Oudompheng

cmd/gc: fix handling of struct padding in hash/eq.

The test case of issue 4585 was not passing due to
miscalculation of memequal args, and the previous fix
does not handle padding at the end of a struct.

Handling of padding at end of structs also fixes the case
of [n]T where T is such a padded struct.

Fixes #4585.
(again)

R=golang-dev, rsc
CC=golang-dev
https://golang.org/cl/7133059
parent 47568c74
......@@ -504,12 +504,17 @@ nod(int op, Node *nleft, Node *nright)
return n;
}
// ispaddedfield returns whether the given field
// is followed by padding. For the case where t is
// the last field, total gives the size of the enclosing struct.
static int
ispaddedfield(Type *t)
ispaddedfield(Type *t, vlong total)
{
if(t->etype != TFIELD)
fatal("ispaddedfield called non-field %T", t);
return t->down != T && t->width + t->type->width != t->down->width;
if(t->down == T)
return t->width + t->type->width != total;
return t->width + t->type->width != t->down->width;
}
int
......@@ -591,7 +596,7 @@ algtype1(Type *t, Type **bad)
for(t1=t->type; t1!=T; t1=t1->down) {
// Blank fields and padding must be ignored,
// so need special compare.
if(isblanksym(t1->sym) || ispaddedfield(t1)) {
if(isblanksym(t1->sym) || ispaddedfield(t1, t->width)) {
ret = -1;
continue;
}
......@@ -2619,7 +2624,7 @@ genhash(Sym *sym, Type *t)
Node *hashel;
Type *first, *t1;
int old_safemode;
int64 size, mul;
int64 size, mul, offend;
if(debug['r'])
print("genhash %S %T\n", sym, t);
......@@ -2705,24 +2710,21 @@ genhash(Sym *sym, Type *t)
// Walk the struct using memhash for runs of AMEM
// and calling specific hash functions for the others.
first = T;
offend = 0;
for(t1=t->type;; t1=t1->down) {
if(t1 != T && algtype1(t1->type, nil) == AMEM && !isblanksym(t1->sym)) {
offend = t1->width + t1->type->width;
if(first == T)
first = t1;
// If it's a memory field but it's padded, stop here.
if(ispaddedfield(t1))
if(ispaddedfield(t1, t->width))
t1 = t1->down;
else
continue;
}
// Run memhash for fields up to this one.
if(first != T) {
if(first->down == t1)
size = first->type->width;
else if(t1 == T)
size = t->width - first->width; // first->width is offset
else
size = t1->width - first->width; // both are offsets
size = offend - first->width; // first->width is offset
hashel = hashmem(first->type);
// hashel(h, size, &p.first)
call = nod(OCALL, hashel, N);
......@@ -2856,6 +2858,7 @@ geneq(Sym *sym, Type *t)
Type *t1, *first;
int old_safemode;
int64 size;
int64 offend;
if(debug['r'])
print("geneq %S %T\n", sym, t);
......@@ -2929,12 +2932,14 @@ geneq(Sym *sym, Type *t)
// and calling specific equality tests for the others.
// Skip blank-named fields.
first = T;
offend = 0;
for(t1=t->type;; t1=t1->down) {
if(t1 != T && algtype1(t1->type, nil) == AMEM && !isblanksym(t1->sym)) {
offend = t1->width + t1->type->width;
if(first == T)
first = t1;
// If it's a memory field but it's padded, stop here.
if(ispaddedfield(t1))
if(ispaddedfield(t1, t->width))
t1 = t1->down;
else
continue;
......@@ -2952,10 +2957,7 @@ geneq(Sym *sym, Type *t)
fn->nbody = list(fn->nbody, eqfield(np, nq, newname(first->sym), neq));
} else {
// More than two fields: use memequal.
if(t1 == T)
size = t->width - first->width; // first->width is offset
else
size = t1->width - first->width; // both are offsets
size = offend - first->width; // first->width is offset
fn->nbody = list(fn->nbody, eqmem(np, nq, newname(first->sym), size, neq));
}
first = T;
......
......@@ -32,6 +32,20 @@ type USmall struct {
A, _, B int32
}
// V has padding but not on the first field.
type V struct {
A1, A2, A3 int32
B int16
C int32
}
// W has padding at the end.
type W struct {
A1, A2, A3 int32
B int32
C int8
}
func test1() {
var a, b U
m := make(map[U]int)
......@@ -84,8 +98,54 @@ func test3() {
}
}
func test4() {
var a, b V
m := make(map[V]int)
copy((*[20]byte)(unsafe.Pointer(&a))[:], "Hello World, Gopher!")
a.A1, a.A2, a.A3, a.B, a.C = 1, 2, 3, 4, 5
b.A1, b.A2, b.A3, b.B, b.C = 1, 2, 3, 4, 5
if a != b {
panic("broken equality: a != b")
}
m[a] = 1
m[b] = 2
if len(m) == 2 {
panic("broken hash: len(m) == 2")
}
if m[a] != 2 {
panic("m[a] != 2")
}
}
func test5() {
var a, b W
m := make(map[W]int)
copy((*[20]byte)(unsafe.Pointer(&a))[:], "Hello World, Gopher!")
a.A1, a.A2, a.A3, a.B, a.C = 1, 2, 3, 4, 5
b.A1, b.A2, b.A3, b.B, b.C = 1, 2, 3, 4, 5
if a != b {
panic("broken equality: a != b")
}
m[a] = 1
m[b] = 2
if len(m) == 2 {
panic("broken hash: len(m) == 2")
}
if m[a] != 2 {
panic("m[a] != 2")
}
}
func main() {
test1()
test2()
test3()
test4()
test5()
}
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