[Bug breakpoints/32079] New: Can't insert internal breakpoints after inferior dlclose some share objects

["blarsen at redhat dot com" <sourceware-bugzilla@sourceware.org>]

https://sourceware.org/bugzilla/show_bug.cgi?id=32079

            Bug ID: 32079
           Summary: Can't insert internal breakpoints after inferior
                    dlclose some share objects
           Product: gdb
           Version: HEAD
            Status: NEW
          Severity: normal
          Priority: P2
         Component: breakpoints
          Assignee: unassigned at sourceware dot org
          Reporter: blarsen at redhat dot com
  Target Milestone: ---

As I'm trying to debug what I think is an unrelated issue in
gdb.base/dlmopen.exp, I noticed that stepping through the program (using next)
GDB gets into a state where it tries to insert some internal breakpoints, and
so refuses to let me move forward, but I can't see the number of the breakpoint
to delete it.

Here's a simplified session:

```
$ ./gdb testsuite/outputs/gdb.base/dlmopen/dlmopen
(gdb) start
[Thread debugging using libthread_db enabled]                                   
Using host libthread_db library "/lib64/libthread_db.so.1".                     

Temporary breakpoint 1, main ()                                                 
    at
/home/gwenthekween/Documents/upstream-build/gdb/testsuite/../../../binutils-gdb/gdb/testsuite/gdb.base/dlmopen
.c:36
36        handle[0] = dlmopen (LM_ID_NEWLM, DSO1_NAME, RTLD_LAZY | RTLD_LOCAL);
(gdb) n
Python Exception <class 'AttributeError'>: module 'gdb' has no attribute
'_handle_missing_debuginfo'
Python Exception <class 'AttributeError'>: module 'gdb' has no attribute
'_handle_missing_debuginfo'
37        assert (handle[0] != NULL);
(gdb) print wait_for_gdb  = 0
$1 = 0
(gdb) handle SIGALRM ignore
Signal        Stop      Print   Pass to program Description
SIGALRM       No        No      No              Alarm clock
(gdb) next

<snip. removing unimportant "next"s>

54        for (dl = 0; dl < 4; ++dl)                     
(gdb)                                                    
56            fun = dlsym (handle[dl], "inc");           
(gdb)                                                    
57            assert (fun != NULL);                      
(gdb)                                                    
59            fun (42);                                  
(gdb)                                                    
61            dlclose (handle[dl]);                      
(gdb)                                                    
warning: error removing breakpoint 0 at 0x7ffff78169b9   
warning: error removing breakpoint 0 at 0x7ffff7730b57   
warning: error removing breakpoint 0 at 0x7ffff7730ad3   
54        for (dl = 0; dl < 4; ++dl)                     
(gdb)                                                    
Warning:                                                 
Cannot insert breakpoint 0.                              
Cannot access memory at address 0x7ffff7730ad3           
Cannot insert breakpoint 0.                              
Cannot access memory at address 0x7ffff7730b57           
Cannot insert breakpoint 0.                              
Cannot access memory at address 0x7ffff78169b9           

Command aborted.                                         
(gdb) p dl                                               
$2 = 2                                                   
(gdb) info break                                         
No breakpoints, watchpoints, tracepoints, or catchpoints.
(gdb) disas /m                           
Dump of assembler code for function main:

<snip unimportant disassembly>

54        for (dl = 0; dl < 4; ++dl)
   0x00000000004012bc <+294>:   movl   $0x0,-0x4(%rbp)
   0x00000000004012c3 <+301>:   jmp    0x401321 <main+395>
=> 0x000000000040131d <+391>:   addl   $0x1,-0x4(%rbp)
   0x0000000000401321 <+395>:   cmpl   $0x3,-0x4(%rbp)
   0x0000000000401325 <+399>:   jle    0x4012c5 <main+303>

<snip disassembly continues>

(gdb)
```

So, this happened after the last dlmopen-lib.1.so was dlclose'd, we are no
longer able to step.

If I set a breakpoint after the loop and continue over it, the issue doesn't
occur, so it seems to be related to internal "next" breakpoints in some way

-- 
You are receiving this mail because:
You are on the CC list for the bug.