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runtime: coalesce 0-size allocations 

Fixes #3996.

R=ken2
CC=golang-dev
https://golang.org/cl/7001052
This commit is contained in:
Russ Cox 2012-12-22 16:42:22 -05:00
parent 295a4d8e64
commit ec59b840f9
1 changed files with 29 additions and 12 deletions
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41
src/pkg/runtime/malloc.goc
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@ -697,14 +697,22 @@ runtime·new(Type *typ, uint8 *ret)
if(raceenabled)
m->racepc = runtime·getcallerpc(&typ);
flag = typ->kind&KindNoPointers ? FlagNoPointers : 0;
ret = runtime·mallocgc(typ->size, flag, 1, 1);
if(UseSpanType && !flag) {
if(false) {
runtime·printf("new %S: %p\n", *typ->string, ret);
if(typ->size == 0) {
// All 0-length allocations use this pointer.
// The language does not require the allocations to
// have distinct values.
ret = (uint8*)&runtime·zerobase;
} else {
flag = typ->kind&KindNoPointers ? FlagNoPointers : 0;
ret = runtime·mallocgc(typ->size, flag, 1, 1);
if(UseSpanType && !flag) {
if(false) {
runtime·printf("new %S: %p\n", *typ->string, ret);
}
runtime·settype(ret, (uintptr)typ | TypeInfo_SingleObject);
}
runtime·settype(ret, (uintptr)typ | TypeInfo_SingleObject);
}
FLUSH(&ret);
@ -719,15 +727,24 @@ runtime·cnew(Type *typ)
if(raceenabled)
m->racepc = runtime·getcallerpc(&typ);
flag = typ->kind&KindNoPointers ? FlagNoPointers : 0;
ret = runtime·mallocgc(typ->size, flag, 1, 1);
if(UseSpanType && !flag) {
if(false) {
runtime·printf("new %S: %p\n", *typ->string, ret);
if(typ->size == 0) {
// All 0-length allocations use this pointer.
// The language does not require the allocations to
// have distinct values.
ret = (uint8*)&runtime·zerobase;
} else {
flag = typ->kind&KindNoPointers ? FlagNoPointers : 0;
ret = runtime·mallocgc(typ->size, flag, 1, 1);
if(UseSpanType && !flag) {
if(false) {
runtime·printf("new %S: %p\n", *typ->string, ret);
}
runtime·settype(ret, (uintptr)typ | TypeInfo_SingleObject);
}
runtime·settype(ret, (uintptr)typ | TypeInfo_SingleObject);
}
return ret;
}