PengZheng commented on issue #723:
URL: https://github.com/apache/celix/issues/723#issuecomment-1908374062
I try to give the following definitions:
**Standard argument should be serializable.** All types except types
involving untyped pointer or double pointer (pointer to pointer) are
serializable. For example, complex types consisting of non-pointer fields are
serializable while complex type containing a untyped pointer field is not
serializable; `[I` is serializable while `[P` and `[**D` are not serializable.
`am=out` parameter should be pointer to text or double pointer to
serializable types.
`am=pre` parameter should be pointer to **trivially copyable type**. It's
safe to apply `memcpy` rivially copyable type without the usual danger of
shallow copy. However, this definition is only meant to make the following code
work:
```C
if (meta ==
DYN_FUNCTION_ARGUMENT_META__PRE_ALLOCATED_OUTPUT) {
void *tmp = NULL;
void **out = (void **) args[i];
size_t size = 0;
dynType_typedPointer_getTypedType(argType, &argType);
status = jsonSerializer_deserializeJson(argType,
result, &tmp);
if (tmp != NULL) {
size = dynType_size(argType);
memcpy(*out, tmp, size);
}
dynType_free(argType, tmp);
```
By this definition, `[D` can not be used as `am=pre`, because
`dynType_free(argType, tmp)` will free the embedded buffer, which has been
copied to `*out` (thus lead to use-after-free). I think the main usage of
SequenceType is to be used as pre-allocated output paramter and let the callee
to fill in actual content. Thus this definition will make SequenceType useless.
Any ideas to make `am=pre` work? @pnoltes
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