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json: explicitly support offsets relative to NULL when dispatching

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Let's trick out UndefinedBehaviourSanitizer:

https://github.com/systemd/systemd/pull/24853#issuecomment-1263380745
This commit is contained in:
Lennart Poettering 2022-09-30 14:09:54 +02:00
parent 84738d864b
commit 0b8218b901
1 changed files with 14 additions and 1 deletions
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15
src/shared/json.c
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@ -4211,6 +4211,19 @@ int json_log_internal(
NULL);
}
static void *dispatch_userdata(const JsonDispatch *p, void *userdata) {
/* When the the userdata pointer is passed in as NULL, then we'll just use the offset as a literal
* address, and convert it to a pointer. Note that might as well just add the offset to the NULL
* pointer, but UndefinedBehaviourSanitizer doesn't like pointer arithmetics based on NULL pointers,
* hence we code this explicitly here. */
if (userdata)
return (uint8_t*) userdata + p->offset;
return SIZE_TO_PTR(p->offset);
}
int json_dispatch(JsonVariant *v, const JsonDispatch table[], JsonDispatchCallback bad, JsonDispatchFlags flags, void *userdata) {
size_t m;
int r, done = 0;
@ -4274,7 +4287,7 @@ int json_dispatch(JsonVariant *v, const JsonDispatch table[], JsonDispatchCallba
found[p-table] = true;
if (p->callback) {
r = p->callback(json_variant_string(key), value, merged_flags, (uint8_t*) userdata + p->offset);
r = p->callback(json_variant_string(key), value, merged_flags, dispatch_userdata(p, userdata));
if (r < 0) {
if (merged_flags & JSON_PERMISSIVE)
continue;