[Bug mi/12555] New: Hangup in MI commands if python StdStringPrinter used on uninitialized std::string

Wed Mar 9 16:03:00 GMT 2011

http://sourceware.org/bugzilla/show_bug.cgi?id=12555

           Summary: Hangup in MI commands if python StdStringPrinter used
                    on uninitialized std::string
           Product: gdb
           Version: 7.1
            Status: NEW
          Severity: normal
          Priority: P2
         Component: mi
        AssignedTo: unassigned@sourceware.org
        ReportedBy: jens.elmenthaler@verigy.com

I have the following code, in combination with the STL pretty printers:

int main() {
    vector<string> names; // Break point here
    names.push_back("German");
    names.push_back("Hola");
    names.push_back("Adios");

    names.pop_back();
    return 0;
}

When the debugger stops at the line declaring "names", gdb hangs, keeping my
linux machine very busy. The problem is that gdb is busy in a MI command sent
by my graphical frontend retrieving all the characters of an uninitialized
string, as the following stack trace shows:

#0  0x0000003d410c38a3 in __pread_nocancel () from /lib64/libc.so.6
#1  0x0000000000492d39 in linux_proc_xfer_partial (ops=0x17b95ed0,
object=TARGET_OBJECT_MEMORY, annex=0x0,
    readbuf=0x2af934ef9bb8 "", writebuf=0x0, offset=263084223400, len=8459111)
at linux-nat.c:4774
#2  0x0000000000493d0e in linux_xfer_partial (ops=0x17b95ed0,
object=TARGET_OBJECT_MEMORY, annex=0x0,
    readbuf=0x2af934ef9bb8 "", writebuf=0x0, offset=263084223400, len=8459111)
at linux-nat.c:5103
#3  0x0000000000490a36 in linux_nat_xfer_partial (ops=0x17b95ed0,
object=TARGET_OBJECT_MEMORY, annex=0x0,
    readbuf=0x2af934ef9bb8 "", writebuf=0x0, offset=263084223400, len=8459111)
at linux-nat.c:3972
#4  0x0000000000586761 in memory_xfer_partial (ops=0x17b95ed0,
object=TARGET_OBJECT_MEMORY, readbuf=0x2af934ef9bb8,
    writebuf=0x0, memaddr=263084223400, len=8459111) at target.c:1335
#5  0x00000000005868e4 in target_xfer_partial (ops=0x17b95ed0,
object=TARGET_OBJECT_MEMORY, annex=0x0,
    readbuf=0x2af934ef9bb8, writebuf=0x0, offset=263084223400, len=8459111) at
target.c:1403
#6  0x0000000000587216 in target_read_partial (ops=0x17b95ed0,
object=TARGET_OBJECT_MEMORY, annex=0x0,
    buf=0x2af934ef9bb8 "", offset=263084223400, len=8459111) at target.c:1679
#7  0x00000000005872dd in target_read (ops=0x17b95ed0,
object=TARGET_OBJECT_MEMORY, annex=0x0,
    buf=0x2af934ec9010
"H\203\372\001H\211\370u\004@\210\067\303I\271\001\001\001\001\001\001\001\001I\211\320H\017\266\326I\017\257\321I\201\370\220",
offset=263084023808, len=8658703) at target.c:1706
#8  0x0000000000586b31 in target_read_memory (memaddr=263084023808,
    myaddr=0x2af934ec9010
"H\203\372\001H\211\370u\004@\210\067\303I\271\001\001\001\001\001\001\001\001I\211\320H\017\266\326I\017\257\321I\201\370\220",
len=8658703) at target.c:1479
#9  0x000000000052a029 in partial_memory_read (memaddr=263084023808,
    myaddr=0x2af934ec9010
"H\203\372\001H\211\370u\004@\210\067\303I\271\001\001\001\001\001\001\001\001I\211\320H\017\266\326I\017\257\321I\201\370\220",
len=8658703, errnoptr=0x7fff762b8818) at valprint.c:1223
#10 0x000000000052a14f in read_string (addr=263084023808, len=8658703, width=1,
fetchlimit=8658703,
    byte_order=BFD_ENDIAN_LITTLE, buffer=0x7fff762b88c8,
bytes_read=0x7fff762b88d4) at valprint.c:1307
#11 0x00000000004df146 in gdbpy_extract_lazy_string (string=0x2af9348baed0,
str_type=0x7fff762b89e8,
    length=0x7fff762b89f0, encoding=0x7fff762b89e0) at
./python/py-lazy-string.c:207
#12 0x00000000004dfd29 in print_string_repr (printer=0x2af93487bb48,
hint=0x17ec55c0 "string", stream=0x17ed5a60,
    recurse=1, options=0x7fff762b8f30, language=0x7c9e60, gdbarch=0x17c9a8f0)
at ./python/py-prettyprint.c:205
#13 0x00000000004e0915 in apply_val_pretty_printer (type=0x17d69d10,
valaddr=0x17fea880 "", embedded_offset=0,
    address=263083557952, stream=0x17ed5a60, recurse=1, options=0x7fff762b8f30,
language=0x7c9e60)
    at ./python/py-prettyprint.c:560
#14 0x000000000052885f in val_print (type=0x17d69d10, valaddr=0x17fea880 "",
embedded_offset=0,
    address=263083557952, stream=0x17ed5a60, recurse=1, options=0x7fff762b8f30,
language=0x7c9e60) at valprint.c:292
#15 0x0000000000528adb in common_val_print (val=0x17f5e510, stream=0x17ed5a60,
recurse=1, options=0x7fff762b8f30,
    language=0x7c9e60) at valprint.c:364
#16 0x00000000004e0702 in print_children (printer=0x2af9349cd878,
hint=0x17e7ef90 "array", stream=0x17ed5a60,
    recurse=0, options=0x7fff762b8f30, language=0x7c9e60) at
./python/py-prettyprint.c:489
#17 0x00000000004e0934 in apply_val_pretty_printer (type=0x17d8b240,
valaddr=0x17ecaf90 "P\201", embedded_offset=0,
    address=140737488339984, stream=0x17ed5a60, recurse=0,
options=0x7fff762b8f30, language=0x7c9e60)
    at ./python/py-prettyprint.c:562
#18 0x000000000052885f in val_print (type=0x17d8b240, valaddr=0x17ecaf90
"P\201", embedded_offset=0,
    address=140737488339984, stream=0x17ed5a60, recurse=0,
options=0x7fff762b8f30, language=0x7c9e60)
    at valprint.c:292
#19 0x0000000000528adb in common_val_print (val=0x17ecad00, stream=0x17ed5a60,
recurse=0, options=0x7fff762b8f30,
    language=0x7c9e60) at valprint.c:364
#20 0x00000000004ca677 in list_args_or_locals (what=locals, values=1,
fi=0x17bd9ad0) at ./mi/mi-cmd-stack.c:354
#21 0x00000000004ca0b1 in mi_cmd_stack_list_locals (command=0x17e72ae0
"stack-list-locals", argv=0x17c55bb0, argc=1)
    at ./mi/mi-cmd-stack.c:155
#22 0x00000000004cf5b8 in mi_cmd_execute (parse=0x17c55a40) at
./mi/mi-main.c:1715
#23 0x00000000004cee89 in captured_mi_execute_command (uiout=0x17be51b0,
data=0x17c55a40) at ./mi/mi-main.c:1517
#24 0x000000000056124e in catch_exception (uiout=0x17be51b0, func=0x4cedbb
<captured_mi_execute_command>,
    func_args=0x17c55a40, mask=6) at exceptions.c:462
#25 0x00000000004cf10f in mi_execute_command (cmd=0x17faa3d0
"26-stack-list-locals --thread 1 --frame 0 1",
    from_tty=1) at ./mi/mi-main.c:1613
#26 0x00000000004cb550 in mi_execute_command_wrapper (cmd=0x17faa3d0
"26-stack-list-locals --thread 1 --frame 0 1")
    at ./mi/mi-interp.c:251
#27 0x000000000056982e in gdb_readline2 (client_data=0x0) at event-top.c:817
#28 0x0000000000568e14 in stdin_event_handler (error=0, client_data=0x0) at
event-top.c:433
#29 0x000000000056758f in handle_file_event (data=...) at event-loop.c:811
#30 0x0000000000566bf9 in process_event () at event-loop.c:393
#31 0x0000000000566cd9 in gdb_do_one_event (data=0x0) at event-loop.c:458
#32 0x00000000005613fc in catch_errors (func=0x566c0e <gdb_do_one_event>,
func_args=0x0, errstring=0x7a3ff8 "",
    mask=6) at exceptions.c:510
#33 0x0000000000566d15 in start_event_loop () at event-loop.c:482
#34 0x00000000004cb5b9 in mi_command_loop (mi_version=2) at
./mi/mi-interp.c:281
#35 0x00000000004cb570 in mi2_command_loop () at ./mi/mi-interp.c:263
#36 0x00000000005619c6 in current_interp_command_loop () at interps.c:288
#37 0x000000000044c563 in captured_command_loop (data=0x0) at ./main.c:226
#38 0x00000000005613fc in catch_errors (func=0x44c552 <captured_command_loop>,
func_args=0x0, errstring=0x75a3e7 "",
    mask=6) at exceptions.c:510
#39 0x000000000044d5bf in captured_main (data=0x7fff762b9680) at ./main.c:905
#40 0x00000000005613fc in catch_errors (func=0x44c595 <captured_main>,
func_args=0x7fff762b9680,
    errstring=0x75a3e7 "", mask=6) at exceptions.c:510
#41 0x000000000044d5f2 in gdb_main (args=0x7fff762b9680) at ./main.c:914
#42 0x000000000044c270 in main (argc=4, argv=0x7fff762b9788) at gdb.c:33

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