Re: No error checking when reading from file using zstd in pg_dump

> On 16 Jun 2025, at 15:56, Tom Lane <tgl@sss.pgh.pa.us> wrote:

> I've not checked to see what the other users of this API do, but
> if they're all like this then we need to fix that comment.

AFAICT all other callers of this API are throwing an error with pg_fatal, and
so does the function in question for ZStd decompression errors.  If we handle
the case of fread() returning 0 to indicate an error like the below *untested
sketch* (with a better error message) this function is fully API compliant as
well.

                /* If we have no more input to consume, we're done */
                if (cnt == 0)
+               {
+                       if (ferror(unconstify(void *, input->src)))
+                               pg_fatal("could not read data to decompress: %m");
+
                        break;
+               }

If this seems like a good approach then Zstd_getc can be simplified as well as
it no longer needs to call ferror, it still needs to check feof though.

--
Daniel Gustafsson