[Beginner Question] How to print the call link graph?

On 7/1/23 02:10, Wen Yi wrote:

Hi community,
I use the gdb to track the postgres like this:

...
pq_getbyte () at pqcomm.c:980
980     in pqcomm.c
(gdb)  next
985     in pqcomm.c
(gdb)  next
986     in pqcomm.c
(gdb)  next
SocketBackend (inBuf=0x7ffc8f7e1310) at postgres.c:372

372     postgres.c: Directory not empty.
(gdb)  next
403     in postgres.c
(gdb)  next
406     in postgres.c
(gdb)  next
407     in postgres.c
(gdb)  next
...

But the question is:
It's too slow to input 'next' to run the postgres, I used to try to use
the  'continut', but the gdb will run the postgres directly and not print
the function name and code line

I want to it print like this:

... -> pq_getbyte () at pqcomm.c:980 -> SocketBackend
(inBuf=0x7ffc8f7e1310) at postgres.c:372 -> ...

Can someone provide me some advice?

If no one here can, then superuser.com, unix.stackexchange.com or
stackoverflow.com should be able to.  (Just don't cross-post...)

--
Born in Arizona, moved to Babylonia.

On Sat, Jul 01, 2023 at 03:10:27PM +0800, Wen Yi wrote:

Hi community,
I use the gdb to track the postgres like this:

...

pq_getbyte () at pqcomm.c:980
980     in pqcomm.c
(gdb)  next
[...]
It's too slow to input 'next' to run the postgres, I used to try to use
the  'continut', but the gdb will run the postgres directly and not
print the function name and code line

I want to it print like this:

... -> pq_getbyte () at pqcomm.c:980 -> SocketBackend (inBuf=0x7ffc8f7e1310) at postgres.c:372 -> ...

Can someone provide me some advice?
Thanks in advance!

I'm not sure what you want to do exactly, but just in case the usual way to do
is to put a breakpoint at the function you're interested in (e.g. "break
exec_simple_query"), or a specific line (e.g. "break filename.c:42"), and then
show the backtrace (backtrace or just bt).

If no one here can, then superuser.com, unix.stackexchange.com or
stackoverflow.com should be able to. (Just don't cross-post...)

If I understand the question this is a GDB question, correct? If so, I would simply set a breakpoint in GDB at that function like so:

b SocketBackend
commands
bt 2
end

this will break then print a backtrace of the last 2 functions (you can remove the 2 to get a full backtrace or change it to some other value). You could also add a continue (c) after the bt to have it run and just print out the backtrace until all is done (save the result to a file using the set logging command)

--
Regards,
Garfield A. Lewis

On 01/07/2023 09:10 CEST Wen Yi <wen-yi@qq.com> wrote:

I use the gdb to track the postgres like this:

...
pq_getbyte () at pqcomm.c:980
980 in pqcomm.c
(gdb) next
985 in pqcomm.c
(gdb) next
986 in pqcomm.c
(gdb) next
SocketBackend (inBuf=0x7ffc8f7e1310) at postgres.c:372

372 postgres.c: Directory not empty.
(gdb) next
403 in postgres.c
(gdb) next
406 in postgres.c
(gdb) next
407 in postgres.c
(gdb) next
...

But the question is:
It's too slow to input 'next' to run the postgres, I used to try to use the
'continut', but the gdb will run the postgres directly and not print the
function name and code line

I want to it print like this:

... -> pq_getbyte () at pqcomm.c:980 -> SocketBackend (inBuf=0x7ffc8f7e1310) at postgres.c:372 -> ...

Can someone provide me some advice?
Thanks in advance!

The Postgres wiki has a page on this topic:

https://wiki.postgresql.org/wiki/Getting_a_stack_trace_of_a_running_PostgreSQL_backend_on_Linux/BSD

Look for "backtrace" and gdb's bt command.

--
Erik

OK, that helps me a lot.
I just want to get the trace of function call.
Thanks very much!

Yours,
Wen Yi