Re: [HACKERS] flexible array members

2011-06-16 Thread Peter Eisentraut 
On ons, 2011-06-15 at 18:19 -0400, Tom Lane wrote:
 Peter Eisentraut pete...@gmx.net writes:
  Is this a route we want to go down?
 
  - GISTENTRY   vector[1];  /* variable-length
 array */
  + GISTENTRY   vector[FLEXIBLE_ARRAY_MEMBER];
 
 Yes, I was thinking about the same trick after noting these warnings
 on Fedora 15, although personally I'd name the macro
 VARIABLE_LENGTH_ARRAY.

This macro is provided by Autoconf and it appears to be using the
standard's terminology.

Actually, the term variable-length array appears to refer to another
C99 feature, namely this one:

void
foo(int n)
{
bar int[n];

do_something();
}



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Re: [HACKERS] flexible array members

2011-06-16 Thread Brar Piening 
On Thu, 16 Jun 2011 22:49:45 +0300, Peter Eisentraut 
pete...@gmx.net wrote:

This macro is provided by Autoconf and it appears to be using the
standard's terminology.


commit dbbba5279f66f95805c1e084e6f646d174931e56 refs/heads/master
Author: Peter Eisentraut pete...@gmx.net
Date:   Thu Jun 16 22:39:09 2011 +0300

Periodically checking my VS2010 patch I noticed that this one broke 
Visual Studio builds.


At least mine and chough 
http://buildfarm.postgresql.org/cgi-bin/show_history.pl?nm=choughbr=HEAD 
in the build farm - I expect others to follow once they rebuild.


error C2065: 'FLEXIBLE_ARRAY_MEMBER' : undeclared identifier
error C2057: expected constant expression

Regards,

Brar

Re: [HACKERS] flexible array members

2011-06-15 Thread Tom Lane 
Peter Eisentraut pete...@gmx.net writes:
 Is this a route we want to go down?

 - GISTENTRY   vector[1];  /* variable-length array */
 + GISTENTRY   vector[FLEXIBLE_ARRAY_MEMBER];

Yes, I was thinking about the same trick after noting these warnings on
Fedora 15, although personally I'd name the macro VARIABLE_LENGTH_ARRAY.

 One thing that is a bit concerning is that throwing more flexible array
 members around the code wherever variable-length arrays are used results
 in crash and burn.  Probably some places are using sizeof or offsetof on
 these structures in incompatible ways.  So each place would have to be
 examined separately.

Hmm, that's nasty.  But from a code-documentation standpoint I think
this is a useful improvement, so it seems worth doing the work to clean
things up.

(I do recall a number of places that assume that sizeof() includes a
single array element ...)

regards, tom lane

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