Re: Gcc 4.4 causes abort in plpython.

Kurt Roeckx wrote:

> #3 0x00000000006c8033 in MemoryContextAlloc (context=0x0, size=112)
> at mcxt.c:507
> #4 0x00000000006abe82 in CopyErrorData () at elog.c:1082
> #5 0x00002b41ea61a755 in PLy_spi_execute_plan (ob=<value optimized out>,
> list=<value optimized out>, limit=<value optimized out>) at plpython.c:2587

It's calling CopyErrorData with CurrentMemoryContext pointing to NULL,
which is not impossible since the GCC-inlined version of
MemoryContextSwitchTo does not check that it wasn't (the other version
does -- should we fix that?).

The question is why is that memory context set to NULL. The code looks
like this:

PLy_spi_execute_plan( ... )
{
MemoryContext oldcontext;
...
oldcontext = CurrentMemoryContext;
PG_TRY();
{
...
}
PG_CATCH();
{
MemoryContextSwitchTo(oldcontext);
CopyErrorData();
...
}

This has been like this for quite a while, which I find surprising
because I got scolded for a similar coding pattern awhile back. I think
I found that the variable was reversed to the value it had on entering
the block by the longjmp call. (IIRC Tom complained because his
compiler threw a "variable might be clobbered by longjmp" warning). We
at Command Prompt also had a similar case on the then-proprietary
Replicator code.

I think a simplistic solution is to declare the variable volatile.
Would you test that and report back?

Thanks.

--
Alvaro Herrera http://www.CommandPrompt.com/
The PostgreSQL Company - Command Prompt, Inc.