Horton

Re: safer node casting

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

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From: Tom Lane <tgl@sss.pgh.pa.us>
To: Andres Freund <andres@anarazel.de>
Cc: Peter Eisentraut <peter.eisentraut@2ndquadrant.com>, pgsql-hackers <pgsql-hackers@postgresql.org>
Date: 2017-02-24T15:54:29Z
Lists: pgsql-hackers 
Andres Freund <andres@anarazel.de> writes:
> Those aren't actually equivalent, because of the !nodeptr. IsA() crashes
> for NULL pointers, but the new code won't. Which means 9ba8a9ce4548b et
> al actually weakened some asserts.

> Should we perhaps have one NULL accepting version (castNodeNull?) and
> one that separately asserts that ptr != NULL?

-1 ... if you're going to use something in a way that requires it not to
 be null, your code will crash quite efficiently on a null, with or
 without an assert.  I don't think we need the extra cogitive burden of
 two distinct macros for this.

			regards, tom lane

Commits

  1. Suppress unused-variable warning.

  2. Make more use of castNode()

  3. Add castNode(type, ptr) for safe casting between NodeTag based types.

  4. Use the new castNode() macro in a number of places.