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Code Issues 1 Releases Wiki Activity

Be more careful about data alignment

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Alingment issues can happen anywhere we do casting
on pointer types. Be more careful in the peg module about
ensuring that pointers are aligned well.
This commit is contained in:
Calvin Rose 2019-02-24 13:43:38 -05:00
parent 327d2ed849
commit 9495be328c
2 changed files with 13 additions and 4 deletions
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15
src/core/peg.c
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@ -987,15 +987,24 @@ static JanetAbstractType peg_type = {
NULL
};
/* Used to ensure that if we place several arrays in one memory chunk, each
* array will be correctly aligned */
static size_t size_padded(size_t offset, size_t size) {
size_t x = size + offset - 1;
return x - (x % size);
}
/* Convert Builder to Peg (Janet Abstract Value) */
static Peg *make_peg(Builder *b) {
size_t bytecode_start = size_padded(sizeof(Peg), sizeof(uint32_t));
size_t bytecode_size = janet_v_count(b->bytecode) * sizeof(uint32_t);
size_t constants_start = size_padded(bytecode_start + bytecode_size, sizeof(Janet));
size_t constants_size = janet_v_count(b->constants) * sizeof(Janet);
size_t total_size = bytecode_size + constants_size + sizeof(Peg);
size_t total_size = constants_start + constants_size;
char *mem = janet_abstract(&peg_type, total_size);
Peg *peg = (Peg *)mem;
peg->bytecode = (uint32_t *)(mem + sizeof(Peg));
peg->constants = (Janet *)(mem + sizeof(Peg) + bytecode_size);
peg->bytecode = (uint32_t *)(mem + bytecode_start);
peg->constants = (Janet *)(mem + constants_start);
peg->num_constants = janet_v_count(b->constants);
memcpy(peg->bytecode, b->bytecode, bytecode_size);
memcpy(peg->constants, b->constants, constants_size);

2
src/include/janet.h
View File

@ -711,7 +711,7 @@ struct JanetAbstractHead {
JanetGCObject gc;
const JanetAbstractType *type;
size_t size;
char data[];
long long data[]; /* Use long long to ensure most general alignment */
};
/* Some function definition flags */