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From: "fasching.a91 at gmail dot com" <sourceware-bugzilla@sourceware.org>
To: gdb-prs@sourceware.org
Subject: [Bug python/28825] New: Breakpoints fire multiple times after fork()
 call
Date: Thu, 27 Jan 2022 07:02:59 +0000
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https://sourceware.org/bugzilla/show_bug.cgi?id=3D28825

            Bug ID: 28825
           Summary: Breakpoints fire multiple times after fork() call
           Product: gdb
           Version: 11.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: python
          Assignee: unassigned at sourceware dot org
          Reporter: fasching.a91 at gmail dot com
  Target Milestone: ---

Created attachment 13932
  --> https://sourceware.org/bugzilla/attachment.cgi?id=3D13932&action=3Ded=
it
program and script to reproduce the described behavior

Breakpoints for a function fire multiple times if they happen after a fork(=
),
even though the function is only called once.
This doesn't happen if there's some delay (e.g. a sleep) between the fork()=
 and
the function call.

Steps to reproduce:

1. Required files
--------------------------------------
$ cat fork.c
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>

void bar(void) {
    printf("this is bar()\n");
}

int main(int argc, char **argv) {
    if (!fork())
        exit(0);
    // sleep(1);  // Doesn't happen after sleeping.
    bar();
    return 0;
}


$ cat script.py
import gdb

class Breakpoint(gdb.Breakpoint):
    def stop(self):
        print("breakpoint fired")

bp =3D Breakpoint("bar")
gdb.execute("run")


2. Compile
--------------------------------------
$ gcc -g -O0 -o fork fork.c


3. Run
--------------------------------------
$ gdb --batch -x script.py fork
Breakpoint 1 at 0x115d: file fork.c, line 6.
[Detaching after fork from child process 33489]
breakpoint fired
breakpoint fired
this is bar()
[Inferior 1 (process 33485) exited normally]

I can reproduce this with GDB 8.2 and 11.1 and haven't tried any releases in
between.

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