Re: bugfix: invalid bit/varbit input causes the log file to be unreadable

Quan Zongliang <quanzongliang@gmail.com> writes:
> The reason is that the error message in the bit_in / varbit_in function
> is output directly using %c. Causes the log file to not be decoded
> correctly.

> The attachment is a patch.

I'm really quite skeptical of the premise here.  We do not guarantee that
the postmaster log file is valid in any particular encoding; it'd be
nearly impossible to do so if the cluster contains databases using
different encodings.  So I think you'd be way better off to reformulate
your log-reading code to be less fragile.

Even granting the premise, the proposed patch seems like a significant
decrease in user-friendliness for typical cases.  I'd rather see us
make an effort to print one valid-per-the-DB-encoding character.
Now that we can rely on snprintf to count %s restrictions in bytes,
I think something like this should work:

                         errmsg("\"%.*s\" is not a valid binary digit",
                                pg_mblen(sp), sp)));

But the real problem is that this is only the tip of the iceberg.
You didn't even hit all the %c usages in varbit.c.  A quick grep finds
these other spots that can doubtless be made to do the same thing:

acl.c:899:            elog(ERROR, "unrecognized objtype abbreviation: %c", objtypec);
arrayfuncs.c:507:                                 errdetail("Unexpected \"%c\" character.",
arrayfuncs.c:554:                                     errdetail("Unexpected \"%c\" character.",
arrayfuncs.c:584:                                     errdetail("Unexpected \"%c\" character.",
arrayfuncs.c:591:                                     errdetail("Unmatched \"%c\" character.", '}')));
arrayfuncs.c:633:                                         errdetail("Unexpected \"%c\" character.",
encode.c:184:                 errmsg("invalid hexadecimal digit: \"%c\"", c)));
encode.c:341:                         errmsg("invalid symbol \"%c\" while decoding base64 sequence", (int) c)));
formatting.c:3298:                                          errmsg("unmatched format separator \"%c\"",
jsonpath_gram.c:2390:                         errdetail("unrecognized flag character \"%c\" in LIKE_REGEX predicate",
regexp.c:426:                             errmsg("invalid regular expression option: \"%c\"",
tsvector_op.c:312:            elog(ERROR, "unrecognized weight: %c", char_weight);
tsvector_op.c:872:                         errmsg("unrecognized weight: \"%c\"", char_weight)));
varbit.c:233:                         errmsg("\"%c\" is not a valid binary digit",
varbit.c:258:                         errmsg("\"%c\" is not a valid hexadecimal digit",
varbit.c:534:                         errmsg("\"%c\" is not a valid binary digit",
varbit.c:559:                         errmsg("\"%c\" is not a valid hexadecimal digit",
varlena.c:5589:                     errmsg("unrecognized format() type specifier \"%c\"",
varlena.c:5710:                         errmsg("unrecognized format() type specifier \"%c\"",

and that's just in src/backend/utils/adt/.

            regards, tom lane