We are doing allocation of structs with flexible array members wrong. It should be:
palloc( offsetof(MyStruct, last_member) + num_items * sizeof(ArrayMember) );
See https://github.com/postgres/postgres/blob/master/src/include/c.h#L342-L350.
The reason is that padding may give a different array start location compared to sizeof.
typedef struct MyStruct {
double x;
char y;
int z[];
} MyStruct;
int main(void) {
printf("sizeof: %lu\n", sizeof(MyStruct));
printf("offsetof: %lu\n", offsetof(MyStruct, z));
}The above prints:
We are doing allocation of structs with flexible array members wrong. It should be:
See https://github.com/postgres/postgres/blob/master/src/include/c.h#L342-L350.
The reason is that padding may give a different array start location compared to
sizeof.The above prints: