Re: [bug fix] strerror() returns ??? in a UTF-8/C database with LC_MESSAGES=non-ASCII

Greg Stark <stark(at)mit(dot)edu> writes:
> What would be nicer would be to display the C define, EINVAL, EPERM, etc.
> Afaik there's no portable way to do that though. I suppose we could just
> have a small array or hash table of all the errors we know about and look
> it up.

Yeah, I was just thinking the same thing. We could do

switch (errno)
{
case EINVAL: str = "EINVAL"; break;
case ENOENT: str = "ENOENT"; break;
...
#ifdef EFOOBAR
case EFOOBAR: str = "EFOOBAR"; break;
#endif
...

for all the common or even less-common names, and only fall back on
printing a numeric value if it's something really unusual.

But I still maintain that we should only do this if we can't get a useful
string out of strerror(). There isn't any way to cram this information
into the current usage of %m without doing damage to the readability and
translatability of the string. Our style & translatability guidelines
specifically recommend against assembling messages out of fragments,
and also against sticking in parenthetical additions.

I suppose we could think about inventing another error field rather
than damaging the readability of the primary message string, ie teach
elog that if %m is used it should emit an additional line along the lines
of
ERRNO: EINVAL
However the cost of adding a new column to CSV log format might exceed its
value.

regards, tom lane