Thread: Help Resolving Compiler Errors With enable-dtrace Flag

On 10/20/24 09:30, Barry Walker wrote:
> Hey folks,

> I have compiled vanilla pg16.4 with the same flags and the probes got 
> created and linked as expected with no issues so I'm assuming there is 
> some difference in the custom version that is causing the errors but I'm 
> having a hard time tracking it down. I'm wondering if anyone here has 
> any experience with this error or has any hints as to why the linker 
> can't find these definitions or even just where the actual definitions 
> for these probes should live so I can try to work backwards and see if 
> there is any differences in the custom version that is messing with 
> the linker.

Talking to the folks that created the custom version is not possible?

If you do a diff on:

access/transam/xact.o

between the stock and custom version does it shed any light?

> 
> Thanks!

-- 
Adrian Klaver
adrian.klaver@aklaver.com

Barry Walker <mstrchef7@gmail.com> writes:
> I have compiled vanilla pg16.4 with the same flags and the probes got
> created and linked as expected with no issues so I'm assuming there is some
> difference in the custom version that is causing the errors but I'm having
> a hard time tracking it down. I'm wondering if anyone here has any
> experience with this error or has any hints as to why the linker can't find
> these definitions or even just where the actual definitions for these
> probes should live so I can try to work backwards and see if there is any
> differences in the custom version that is messing with the linker.

I'd read

https://www.postgresql.org/docs/current/dynamic-trace.html#DEFINING-TRACE-POINTS

and then go see if those tracepoints are fully conforming to the
coding rules in the modified version.  A plausible bet is that
their entries in probes.d don't entirely match up with the calls
in the source code.  You could compare the relevant bits of code
between vanilla and modified 16.4 if the problem isn't immediately
obvious.

            regards, tom lane

On 10/20/24 12:02, Barry Walker wrote:
> Unfortunately the people remaining are just as lost as me. No one has 
> attempted to build with dtrace so I'm in uncharted territory.

Was the customization done under version control?

If so then as last resort use bisect or equivalent to find the breaking 
change?

> 
> A diff of the object file doesn't give any useful information, the 
> custom version has a lot of differences since there have been a number 
> of changes from stock. postgresql_transaction__commit_semaphore does 
> exist in the symbol table of both .o files though when compared with 
> objdump.

My mistake, was not paying attention. I meant to point the diff at:

~/src/backend/access/transam/xact.c

-- 
Adrian Klaver
adrian.klaver@aklaver.com

Barry Walker <mstrchef7@gmail.com> writes:
> Yes it was. My thinking though is that I am getting this error with every
> probe, not just the ones in xact.c 

Now you tell us?

If that's the case, I wonder whether probes.o is getting built
correctly and included in the link.  The relevant bits are in
src/backend/Makefile ... they don't look that easy to mess up,
but maybe.

            regards, tom lane