On Tue, 24 Mar 2026 at 14:10, Tender Wang <[email protected]> wrote:
> Actually, I haven't quite figured out why `typLen` cannot be used here.
This is because we sign-extend rather than zero-extend up to Datum.
Consider this code from master:
typedef uint64_t Datum;
static inline Datum
Int32GetDatum(int32 X)
{
return (Datum) X;
}
So we cast to uint64_t when converting int32 to Datum.
And consider the output of this C program:
drowley@amd3990x:~$ cat datum.c
#include <stdio.h>
#include <stdint.h>
int main(void)
{
int32_t i32 = -1;
uint64_t i64 = (uint64_t) i32;
for (int i = 0; i < 64; i++)
{
putchar(i64 & 0x8000000000000000ULL ? '1' : '0');
i64 <<= 1;
}
putchar('\n');
return 0;
}
drowley@amd3990x:~$ gcc datum.c -o datum && ./datum
1111111111111111111111111111111111111111111111111111111111111111
If you only look at the lower 32 bits of that Datum, then you're not
looking at the entire value.
I don't have hardware to try it, but I also don't suppose comparing
the first attlen bytes of a Datum does the same thing on big-endian
machines as that would look at the most significant side of the Datum
rather than the least significant side as it would on little-endian.
David
