Horton

Re: making the backend's json parser work in frontend code

Tom Lane <tgl@sss.pgh.pa.us>

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From: Tom Lane <tgl@sss.pgh.pa.us>
To: Robert Haas <robertmhaas@gmail.com>
Cc: Mahendra Singh Thalor <mahi6run@gmail.com>, Mark Dilger <mark.dilger@enterprisedb.com>, Andrew Dunstan <andrew.dunstan@2ndquadrant.com>, David Steele <david@pgmasters.net>, "pgsql-hackers@postgresql.org" <pgsql-hackers@postgresql.org>
Date: 2020-01-28T16:34:57Z
Lists: pgsql-hackers 
Robert Haas <robertmhaas@gmail.com> writes:
> On Tue, Jan 28, 2020 at 10:30 AM Mahendra Singh Thalor
> <mahi6run@gmail.com> wrote:
>> Tom Lane already fixed this and committed yesterday(4589c6a2a30faba53d0655a8e).

> Oops. OK, thanks.

Yeah, there were multiple issues here:

1. If a switch is expected to cover all values of an enum type,
we now prefer not to have a default: case, so that we'll get
compiler warnings if somebody adds an enum value and fails to
update the switch.

2. Without a default:, though, you need to have after-the-switch
code to catch the possibility that the runtime value was not a
legal enum element.  Some compilers are trusting and assume that
that's not a possible case, but some are not (and Coverity will
complain about it too).

3. Some compilers still don't understand that elog(ERROR) doesn't
return, so you need a dummy return.  Perhaps pg_unreachable()
would do as well, but project style has been the dummy return for
a long time ... and I'm not entirely convinced by the assumption
that every compiler understands pg_unreachable(), anyway.

(I know Robert knows all this stuff, even if he momentarily
forgot.  Just summarizing for onlookers.)

			regards, tom lane

Commits

  1. Add jsonapi.c to Mkvcbuild.pm's @pgcommonallfiles.

  2. Move jsonapi.c and jsonapi.h to src/common.

  3. Move some code from jsonapi.c to jsonfuncs.c.

  4. Adjust pg_parse_json() so that it does not directly ereport().

  5. Remove jsonapi.c's lex_accept().

  6. Split JSON lexer/parser from 'json' data type support.

  7. Rationalize code placement between wchar.c, encnames.c, and mbutils.c.

  8. Move wchar.c and encnames.c to src/common/.

  9. Update header comments for wchar.c and encnames.c.

  10. Make StringInfo available to frontend code.

  11. Use SASLprep to normalize passwords for SCRAM authentication.