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Add janet_abstract_begin and janet_abstract_end

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This will allow some one constructing an abstract to
only make it visible to the garbage collector after it
is in a valid state. If code in the constructing cfunction
panics before janet_abstract_end is called, the GC will not try
to mark the incomplete abstract type. This is often not needed through
careful programming, but should work well.
This commit is contained in:
Calvin Rose 2019-06-20 12:37:57 -04:00
parent 4b4fe80404
commit 522545287e
3 changed files with 19 additions and 3 deletions
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13
src/core/abstract.c
View File

@ -26,10 +26,19 @@
#endif
/* Create new userdata */
void *janet_abstract(const JanetAbstractType *atype, size_t size) {
JanetAbstractHead *header = janet_gcalloc(JANET_MEMORY_ABSTRACT,
void *janet_abstract_begin(const JanetAbstractType *atype, size_t size) {
JanetAbstractHead *header = janet_gcalloc(JANET_MEMORY_NONE,
sizeof(JanetAbstractHead) + size);
header->size = size;
header->type = atype;
return (void *) & (header->data);
}
void *janet_abstract_end(void *x) {
janet_gc_settype((void *)(janet_gc_header(x)), JANET_MEMORY_ABSTRACT);
return x;
}
void *janet_abstract(const JanetAbstractType *atype, size_t size) {
return janet_abstract_end(janet_abstract_begin(atype, size));
}

5
src/core/peg.c
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@ -990,6 +990,11 @@ static void peg_unmarshal(void *p, JanetMarshalContext *ctx) {
peg->bytecode = NULL;
peg->constants = NULL;
/* Ensure not too large */
if (constants_start + sizeof(Janet) * peg->num_constants > janet_abstract_size(p)) {
janet_panic("size mismatch");
}
for (size_t i = 0; i < peg->bytecode_len; i++)
bytecode[i] = (uint32_t) janet_unmarshal_int(ctx);
for (uint32_t j = 0; j < peg->num_constants; j++)

4
src/include/janet.h
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@ -1219,7 +1219,9 @@ JANET_API const JanetKV *janet_dictionary_next(const JanetKV *kvs, int32_t cap,
#define janet_abstract_head(u) ((JanetAbstractHead *)((char *)u - offsetof(JanetAbstractHead, data)))
#define janet_abstract_type(u) (janet_abstract_head(u)->type)
#define janet_abstract_size(u) (janet_abstract_head(u)->size)
JANET_API void *janet_abstract(const JanetAbstractType *type, size_t size);
JANET_API void *janet_abstract_begin(const JanetAbstractType *type, size_t size);
JANET_API void *janet_abstract_end(void *);
JANET_API void *janet_abstract(const JanetAbstractType *type, size_t size); /* begin and end in one call */
/* Native */
typedef void (*JanetModule)(JanetTable *);