Horton

Re: Large writable variables

Peter Eisentraut <peter.eisentraut@2ndquadrant.com>

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From: Peter Eisentraut <peter.eisentraut@2ndquadrant.com>
To: Andres Freund <andres@anarazel.de>
Cc: pgsql-hackers@postgresql.org, Thomas Munro <thomas.munro@enterprisedb.com>
Date: 2018-10-18T20:20:29Z
Lists: pgsql-hackers 
On 18/10/2018 22:17, Peter Eisentraut wrote:
> On 17/10/2018 23:51, Andres Freund wrote:
>>> __builtin_types_compatible_p(const char *, char *) returns false (0) for me.
>>
>> Right, that's why I added a const, inside the macro,  to the type
>> specified in the unconstify argument. So typeof() yields a const char *,
>> and the return type is specified as char *, and adding a const in the
>> argument also yields a const char *.
> 
> Yeah, that works.  The C++-inspired version also allowed casting from
> not-const to const, which we don't really need.

> Attached is my previous patch adapted to your macro.

Oh, I forgot to mention, your version doesn't work for this code in
pqexpbuffer.c:

    str->data = (char *) oom_buffer;

That's probably not a big deal though.

-- 
Peter Eisentraut              http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services

Commits

  1. Apply unconstify() in more places

  2. Improve unconstify() documentation

  3. Drop const cast from dlsym() calls

  4. Const-ify a few more large static tables.

  5. Improve tzparse's handling of TZDEFRULES ("posixrules") zone data.

  6. Avoid statically allocating statement cache in ecpglib/prepare.c.

  7. Reorder FmgrBuiltin members, saving 25% in size.

  8. Add macro to cast away const without allowing changes to underlying type.

  9. Mark constantly allocated dest receiver as const.

  10. Avoid statically allocating formatting.c's format string caches.

  11. Correct constness of system attributes in heap.c & prerequisites.

  12. Avoid statically allocating gmtsub()'s timezone workspace.

  13. Correct constness of a few variables.

  14. Move the replication lag tracker into heap memory.