Horton

Re: ECPG cleanup and fix for clang compile-time problem

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

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From: Tom Lane <tgl@sss.pgh.pa.us>
To: pgsql-hackers@lists.postgresql.org
Cc: Andres Freund <andres@anarazel.de>, Peter Eisentraut <peter_e@gmx.net>, Michael Paquier <michael.paquier@gmail.com>
Date: 2024-04-19T15:21:05Z
Lists: pgsql-hackers 
One other bit of randomness that I noticed: ecpg's parse.pl has
this undocumented bit of logic:

                if ($a eq 'IDENT' && $prior eq '%nonassoc')
                {

                    # add more tokens to the list
                    $str = $str . "\n%nonassoc CSTRING";
                }

The net effect of that is that, where gram.y writes

%nonassoc    UNBOUNDED NESTED /* ideally would have same precedence as IDENT */
%nonassoc    IDENT PARTITION RANGE ROWS GROUPS PRECEDING FOLLOWING CUBE ROLLUP
             SET KEYS OBJECT_P SCALAR VALUE_P WITH WITHOUT PATH
%left        Op OPERATOR      /* multi-character ops and user-defined operators */

preproc.c has

 %nonassoc UNBOUNDED NESTED
 %nonassoc IDENT
%nonassoc CSTRING PARTITION RANGE ROWS GROUPS PRECEDING FOLLOWING CUBE ROLLUP
 SET KEYS OBJECT_P SCALAR VALUE_P WITH WITHOUT PATH
 %left Op OPERATOR

If you don't find that scary as heck, I suggest reading the very long
comment just in front of the cited lines of gram.y.  The argument why
assigning these keywords a precedence at all is OK depends heavily
on it being the same precedence as IDENT, yet here's ECPG randomly
breaking that.

We seem to have avoided problems though, because if I fix things
by manually editing preproc.y to re-join the lines:

 %nonassoc IDENT CSTRING PARTITION RANGE ROWS GROUPS PRECEDING FOLLOWING CUBE ROLLUP

the generated preproc.c doesn't change at all.  Actually, I can
take CSTRING out of this list altogether and it still doesn't
change the results ... although looking at how CSTRING is used,
it looks safer to give it the same precedence as IDENT.

I think we should change parse.pl to give one or the other of these
results before something more serious breaks there.

			regards, tom lane

Commits

  1. ecpg: clean up some other assorted memory leaks.

  2. ecpg: fix some memory leakage of data-type-related structures.

  3. ecpg: put all string-valued tokens returned by pgc.l in local storage.

  4. ecpg: fix more minor mishandling of bad input in preprocessor.

  5. ecpg: fix some minor mishandling of bad input in preprocessor.

  6. ecpg: avoid breaking the IDENT precedence level in two.

  7. ecpg: improve preprocessor's memory management.

  8. ecpg: move some functions into a new file ecpg/preproc/util.c.

  9. ecpg: re-implement preprocessor's string management.

  10. ecpg: major cleanup, simplification, and documentation of parse.pl.

  11. ecpg: remove check_rules.pl.

  12. ecpg: clean up documentation of parse.pl, and add more input checking.

  13. Clean up indentation and whitespace inconsistencies in ecpg.

  14. Exclude flex-generated code from coverage testing