[PATCH] 0001-Fix-multi-thread-debug-bug-in-AIX.patch

[Aditya Kamath1 <Aditya.Kamath1@ibm.com>]

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Hi all,

In the latest gdb AIX users aren't able to debug multi threaded programs.

I have fixed it. Please find attached the patch. [See 0001-Fix-multi-thread-debug-bug-in-AIX.patch].

Also pasting the output of the failure and the output after adding the patch.

Kindly let me know if any change required, if not kindly push this patch so that AIX folks have a happy multi threaded debugging.

Have a nice day ahead.

Thanks and regards,
Aditya.

---------------------------------------------------------

The code:- [Program Credits:- GDB TESTSUITE gdb_threads/continue-pending-status.c ]


#include <unistd.h>

#include <stdlib.h>

#include <pthread.h>

#include <assert.h>


pthread_barrier_t barrier;


#define NUM_THREADS 2


void *

thread_function (void *arg)

{

  pthread_barrier_wait (&barrier);

  while (1);

}


int

main (void)

{

  int i;


  alarm (300);


  pthread_barrier_init (&barrier, NULL, NUM_THREADS);


  for (i = 0; i < NUM_THREADS; i++)

    {

      pthread_t thread;

      int res;


      res = pthread_create (&thread, NULL,

                            thread_function, NULL);

      assert (res == 0);

    }


  while (1)

    sleep (1);


  return 0;

}

OUTPUT BEFORE PATCH:-


(gdb) r

Starting program: /home/gdb_tests/continue-pending-status

[New Thread 1]

./../gdbsupport/gdb-checked-static-cast.h:58: internal-error: checked_static_cast: Assertion `result != nullptr' failed.

A problem internal to GDB has been detected,

further debugging may prove unreliable.

----- Backtrace -----

0x1010fb657 ???

0x1010fb81f ???


OUTPUT AFTER PATCH


(gdb) r

Starting program: /home/gdb_tests/continue-pending-status

[New Thread 1]

^C[New Thread 258]

[New Thread 515]


Thread 1 received signal SIGINT, Interrupt.

0xd0595fb0 in _p_nsleep () from /usr/lib/libpthread.a(shr_xpg5.o)

(gdb) info threads

  Id   Target Id                          Frame

* 1    process 7602548                    0xd0595fb0 in _p_nsleep ()

   from /usr/lib/libpthread.a(shr_xpg5.o)

  2    Thread 1 (tid 27984319, running)   0xd0595fb0 in _p_nsleep ()

   from /usr/lib/libpthread.a(shr_xpg5.o)

  3    Thread 258 (tid 37093859, running) thread_function (arg=0x0)

    at continue-pending-status.c:36

  4    Thread 515 (tid 35062111, running) thread_function (arg=warning: (Internal error: pc 0x0 in read in psymtab, but not in symtab.)


0x0)

    at continue-pending-status.c:36

(gdb) q



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From 15797e8153fd90e6f457cc3bcd0237fbfd4491d4 Mon Sep 17 00:00:00 2001
From: Aditya Vidyadhar Kamath <Aditya.Kamath1@ibm.com>
Date: Tue, 25 Oct 2022 01:35:33 -0500
Subject: [PATCH] Fix multi thread debug bug in AIX

In the recent commit 98ed24fb35d89eb20179edf6c12f599c7a9e228e made by Mr. Tom there is a change in aix-thread.c file that changes

 static_cast <aix_thread_info *> in gdb to gdb::checked_static_cast <aix_thread_info *>

AIX folks using the latest version will not be able to debug multi thread programs as a result of it.

The error in AIX is as follows:-

internal-error: checked_static_cast: Assertion 'result != nullptr' failed.

The reason is that the first thread in a multi threaded program will not have a prev.

Hence we need to add this check.

The future threads if any will handle the change gdb::checked_static_cast with ease after this condition is checked.
---
 gdb/aix-thread.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/gdb/aix-thread.c b/gdb/aix-thread.c
index e556c153576..b2dabd242fc 100644
--- a/gdb/aix-thread.c
+++ b/gdb/aix-thread.c
@@ -90,6 +90,9 @@ struct aix_thread_info : public private_thread_info
 static aix_thread_info *
 get_aix_thread_info (thread_info *thread)
 {
+  if (thread->priv == NULL)
+    return NULL;
+
   return gdb::checked_static_cast<aix_thread_info *> (thread->priv.get ());
 }
 
-- 
2.31.1