[Bug threads/15520] New: GDB step command crashed on non-stop mode

["wei_si.a.xiao@alcatel-lucent.com" <sourceware-bugzilla@sourceware.org>]

http://sourceware.org/bugzilla/show_bug.cgi?id=15520

             Bug #: 15520
           Summary: GDB step command crashed on non-stop mode
           Product: gdb
           Version: 7.6
            Status: NEW
          Severity: critical
          Priority: P2
         Component: threads
        AssignedTo: unassigned@sourceware.org
        ReportedBy: wei_si.a.xiao@alcatel-lucent.com
    Classification: Unclassified


I am using GDB non-stop mode to debug a multi-thread application. But it always
crashed when I use “step” command. I have tried version 7.4/7.5.1/7.6, the
result are same. The issue does not exist if we don’t use non-stop mode.
I have written a small program to test, easy to reproduce each time. The code
as below:

// test.cc
#include <string>
using namespace std;
void fun(string &str1, string &str2)
{
    str1 += str2;
}

int main(void)
{
   string str1 = "abc";
   string str2 = "def";
   fun(str1,str2);

   return 0;
}


Compile:
g++ -g test.cc -o test


The procedure for reproduce as below:
vm10-0-0-1:/root-# gdb ./test
GNU gdb (GDB) 7.6
Copyright (C) 2013 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.  Type "show copying"
and "show warranty" for details.
This GDB was configured as "x86_64-unknown-linux-gnu".
For bug reporting instructions, please see:
<http://www.gnu.org/software/gdb/bugs/>...
Reading symbols from /root/test...done.
(gdb) set target-async 1
(gdb) set non-stop on
(gdb) break fun Breakpoint 1 at 0x4007b4: file test.cc, line 5.
(gdb) run
Starting program: /root/test 

Breakpoint 1, fun (str1=..., str2=...) at test.cc:5
5           str1 += str2;
(gdb) step
6       }
(gdb) step

Program received signal SIGSEGV, Segmentation fault.
fun (str1=<error reading variable: Cannot access memory at address
0xfffffffffffffff8>, str1@entry=<error reading variable: Cannot access memory
at address 0x8>,
    str2=<error reading variable: Cannot access memory at address
0xfffffffffffffff0>, str2@entry=<error reading variable: Cannot access memory
at address 0x8>) at test.cc:6
6       }
(gdb)

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>From gdb-prs-return-13727-listarch-gdb-prs=sources.redhat.com@sourceware.org Thu May 23 07:09:32 2013
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From: "pmuldoon at redhat dot com" <sourceware-bugzilla@sourceware.org>
To: gdb-prs@sourceware.org
Subject: [Bug c++/15519] GDB 7.6 is 94x slower than GDB 7.5.1 using a certain
 core file
Date: Thu, 23 May 2013 07:09:00 -0000
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http://sourceware.org/bugzilla/show_bug.cgi?id\x15519

--- Comment #3 from Phil Muldoon <pmuldoon at redhat dot com> 2013-05-23 07:09:30 UTC ---
Created attachment 7039
  --> http://sourceware.org/bugzilla/attachment.cgi?idp39
pdf summary of call graph

Sometimes I find the summary graph produced by dot -Tpdf from the output
provided by gprof2dot handy as a visual overview.  Was just looking at the
output this morning out of curiosity and am attaching this file to see if it is
useful for others looking at this bug

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