[Bug breakpoints/15729] New: gdb/MI error inserting new breakpoint

["sirnewton_01 at yahoo dot ca" <sourceware-bugzilla at sourceware dot org>]

http://sourceware.org/bugzilla/show_bug.cgi?id=15729

            Bug ID: 15729
           Summary: gdb/MI error inserting new breakpoint
           Product: gdb
           Version: 7.6
            Status: NEW
          Severity: normal
          Priority: P2
         Component: breakpoints
          Assignee: unassigned at sourceware dot org
          Reporter: sirnewton_01 at yahoo dot ca

I am trying to add a breakpoint using gdb/MI on Linux x86_64. Whenever I add it
I get an error message like '^error,msg="Cannot access memory at address
0x400c3d"'

Here's my setup:
1) Launch gdb like the following: "gdb -i=mi <path_to_program>"
2) Set the following option: "-gdb-set target-async 1"
3) Set the following option: "-gdb-set non-stop on"
4) Start the program: "-exec-run"
5) Attempt to set a breakpoint "-break-insert some_func"

Result:
I get the error message above. The same error shows up even if I try the '-f'
option of the "-break-insert" command.

Expected Result:
The breakpoint is added or an error message indicating that break points can't
be added unless the thread is stopped.

After some debugging I discovered that one of the differences between setting
the breakpoint when the thread is stopped versus running is in the following
function: memory_xfer_partial_1 in target.c. In the successful case line 1556
is false and "inf" is set to NULL. In the failure case "inf" is assigned to a
non-NULL value and the error is presented.

Here is the backtrace that leads back to the error:
#0  memory_error (status=5, memaddr=4197437) at corefile.c:200
#1  0x0000000000591729 in read_memory (memaddr=4197437, 
    myaddr=<optimized out>, len=<optimized out>) at corefile.c:223
#2  0x000000000059183d in read_memory_unsigned_integer (
    memaddr=<optimized out>, len=1, byte_order=BFD_ENDIAN_LITTLE)
    at corefile.c:312
#3  0x000000000040a228 in amd64_analyze_prologue (gdbarch=0x20d7cd0, 
    pc=4197437, current_pc=18446744073709551615, cache=0x7fff8b60c460)
    at amd64-tdep.c:2126
#4  0x000000000040ad57 in amd64_skip_prologue (gdbarch=0x20d7cd0, 
    start_pc=4197437) at amd64-tdep.c:2273
#5  0x00000000004f5f8b in skip_prologue_sal (sal=0x7fff8b60c760)
    at symtab.c:2869
#6  0x00000000004f62d7 in find_function_start_sal (sym=0x214ac30, 
    funfirstline=1) at symtab.c:2782
#7  0x000000000050360d in symbol_to_sal (result=0x7fff8b60c880, 
    funfirstline=<optimized out>, sym=0x214ac30) at linespec.c:3622
#8  0x00000000005042c1 in convert_linespec_to_sals (state=0x7fff8b60ccc0, 
    ls=0x7fff8b60cd00) at linespec.c:2028
#9  0x00000000005069fc in parse_linespec (parser=0x7fff8b60cc90, 
    argptr=<optimized out>) at linespec.c:2319
#10 0x00000000005073f5 in decode_line_full (argptr=0x7fff8b60cf48, 
    flags=<optimized out>, default_symtab=<optimized out>, 
    default_line=<optimized out>, canonical=0x7fff8b60cf50, select_mode=0x0, 
    filter=0x0) at linespec.c:2430
#11 0x00000000004b79ea in parse_breakpoint_sals (address=0x7fff8b60cf48, 
    canonical=0x7fff8b60cf50) at breakpoint.c:9323
#12 0x00000000004bfab1 in create_breakpoint (gdbarch=0x2105a00, 
    arg=0x20d4109 "", cond_string=0x0, thread=-1, extra_string=0x0, 
    parse_condition_and_thread=0, tempflag=0, type_wanted=bp_breakpoint, 
    ignore_count=0, pending_break_support=AUTO_BOOLEAN_FALSE, 
    ops=0xae6640 <bkpt_breakpoint_ops>, from_tty=0, enabled=1, internal=0, 
    flags=0) at breakpoint.c:9554
#13 0x000000000047a114 in mi_cmd_break_insert (command=<optimized out>, 
    argv=<optimized out>, argc=<optimized out>) at ./mi/mi-cmd-break.c:186
#14 0x00000000004807fd in mi_cmd_execute (parse=0x2107e70)
    at ./mi/mi-main.c:2133
#15 captured_mi_execute_command (context=0x2107e70, uiout=0x20d11e0)
    at ./mi/mi-main.c:1884
#16 mi_execute_command (cmd=0x20fb9e0 "-break-insert main.main", 
    from_tty=<optimized out>) at ./mi/mi-main.c:2003
#17 0x000000000047bacd in mi_execute_command_wrapper (cmd=<optimized out>)
    at ./mi/mi-interp.c:311
#18 mi_execute_command_input_handler (cmd=<optimized out>)
    at ./mi/mi-interp.c:319
#19 0x000000000052c8b3 in process_event () at event-loop.c:342
    at ./mi/mi-main.c:1884
#16 mi_execute_command (cmd=0x20fb9e0 "-break-insert main.main", 
    from_tty=<optimized out>) at ./mi/mi-main.c:2003
#17 0x000000000047bacd in mi_execute_command_wrapper (cmd=<optimized out>)
    at ./mi/mi-interp.c:311
#18 mi_execute_command_input_handler (cmd=<optimized out>)
    at ./mi/mi-interp.c:319
#19 0x000000000052c8b3 in process_event () at event-loop.c:342
#20 process_event () at event-loop.c:314
#21 0x000000000052cc78 in gdb_do_one_event () at event-loop.c:406
#22 0x000000000052ce15 in start_event_loop () at event-loop.c:431
#23 0x0000000000526293 in captured_command_loop (data=<optimized out>)
    at main.c:258
#24 0x0000000000524e4b in catch_errors (func=0x526280 <captured_command_loop>, 
    func_args=0x0, errstring=0x6e1f93 "", mask=6) at exceptions.c:546
#25 0x0000000000526bf6 in captured_main (data=<optimized out>) at main.c:1041
#26 0x0000000000524e4b in catch_errors (func=0x526590 <captured_main>, 
    func_args=0x7fff8b60d3d0, errstring=0x6e1f93 "", mask=6)
    at exceptions.c:546
#27 0x0000000000527584 in gdb_main (args=<optimized out>) at main.c:1050
#28 0x000000000040769e in main (argc=<optimized out>, argv=<optimized out>)
    at gdb.c:34

Here are the records of my steps through the code in the success and failure
cases:

failure path through memory_xfer_partial_1:
Breakpoint 1, memory_xfer_partial_1 (ops=0x141bac0, 
    object=TARGET_OBJECT_MEMORY, readbuf=0x7fffd028cb90, writebuf=0x0, 
    memaddr=4197437, len=18) at target.c:1434
1434      if (readbuf != NULL && overlay_debugging)
(gdb) n
1454      if (readbuf != NULL && trust_readonly)
(gdb) n
1476      if (readbuf != NULL && get_traceframe_number () != -1)
(gdb) n
1527      region = lookup_mem_region (memaddr);
(gdb) n
1529      if (memaddr + len < region->hi || region->hi == 0)
(gdb) n
1530        reg_len = len;
(gdb) n
1534      switch (region->attrib.mode)
(gdb) n
1556      if (!ptid_equal (inferior_ptid, null_ptid))
(gdb) n
1557        inf = find_inferior_pid (ptid_get_pid (inferior_ptid));
(gdb) n
1561      if (inf != NULL
(gdb) n
1565          && get_traceframe_number () == -1
(gdb) n
1566          && (region->attrib.cache
(gdb) n
1567          || (stack_cache_enabled_p && object ==
TARGET_OBJECT_STACK_MEMORY)))
(gdb) n
1597          res = ops->to_xfer_partial (ops, TARGET_OBJECT_MEMORY, NULL,
(gdb) n
1599          if (res > 0)
(gdb) n
1604          if (ops->to_has_all_memory (ops))
(gdb) n
1605        break;
(gdb) n
1615      if (res > 0
(gdb) n
1627      return res;
(gdb) n
1628    }
(gdb) n
memory_xfer_partial (ops=0x141bac0, object=TARGET_OBJECT_MEMORY, 
    readbuf=0x7fffd028cb90, writebuf=0x0, memaddr=4197437, len=18)
    at target.c:1651
1651          if (res > 0 && !show_memory_breakpoints)
(gdb) print res
$1 = 0


successful path through memory_xfer_partial_1:
Breakpoint 1, memory_xfer_partial_1 (ops=0xbf27c0 <exec_ops>, 
    object=TARGET_OBJECT_MEMORY, readbuf=0x7fffd028cb90, writebuf=0x0, 
    memaddr=4197437, len=18) at target.c:1434
1434      if (readbuf != NULL && overlay_debugging)
(gdb) n
1454      if (readbuf != NULL && trust_readonly)
(gdb) n
1476      if (readbuf != NULL && get_traceframe_number () != -1)
(gdb) n
1527      region = lookup_mem_region (memaddr);
(gdb) n
1529      if (memaddr + len < region->hi || region->hi == 0)
(gdb) n
1530        reg_len = len;
(gdb) n
1534      switch (region->attrib.mode)
(gdb) n
1556      if (!ptid_equal (inferior_ptid, null_ptid))
(gdb) n
1559        inf = NULL;
(gdb) n
1561      if (inf != NULL
(gdb) n
1597          res = ops->to_xfer_partial (ops, TARGET_OBJECT_MEMORY, NULL,
(gdb) n
1599          if (res > 0)
(gdb) n
1600        break;
(gdb) n
1615      if (res > 0
(gdb) n
1616          && inf != NULL
(gdb) n
1627      return res;
(gdb) n
1628    }
(gdb) n
memory_xfer_partial (ops=0xbf27c0 <exec_ops>, object=TARGET_OBJECT_MEMORY, 
    readbuf=0x7fffd028cb90, writebuf=0x0, memaddr=4197437, len=18)
    at target.c:1651
1651          if (res > 0 && !show_memory_breakpoints)
(gdb) print res
$3 = 18

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