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Re: [RFC-v5] Fix .text section offset for windows DLL (was Calling __stdcall functions in the inferior)

On 2012-12-8 0:27, Pierre Muller wrote: 

-----Message d'origine-----
De : gdb-patches-owner@sourceware.org [mailto:gdb-patches-
owner@sourceware.org] De la part de asmwarrior
Envoyà : vendredi 7 dÃcembre 2012 17:17
à : Pierre Muller
Cc : 'Joel Brobecker'; 'Eli Zaretskii'; gdb-patches@sourceware.org
Objet : Re: [RFC-v5] Fix .text section offset for windows DLL (was Calling
__stdcall functions in the inferior)

On 2012-12-7 23:40, Pierre Muller wrote: 
    Hi Yuanhui,
thanks for trying to debug this...

    First, concerning the optimized out problems,
it would be easier if you would recompile
GDB without optimization:

make clean all CFLAGS="-gdwarf-2 -O0"

After that, you should get optimized out variables...
I will did this if I have more time.


    I also installed CodeBlocks to test if I can reproduce your crash,
but I never got any ...
The codeblocks.exe was built myself, which has debug information in it. 
  I tried to recompile the sources, but
compilation fails on not found wxWorks headers...
Despite the fact that I compiled wxWorks 2.9.4 without problems.
Note: Codeblocks currently can build against wxWidgets 2.8.12 library. I think it was not stable to build against wxWidgets 2.9.x.

    Could it be that some weird DLL's have unnamed
sections?
    Could you try to insert
      if (sections[i] && section[i].name)
before

       if (strcmp (sections[i].section_name, section_name) == 0)
         return i;
to confirm that the problem originates here?

I add a line:
static int
get_pe_section_index (const char *section_name,
		      struct read_pe_section_data *sections,
		      int nb_sections)
{
    int i;
    for (i = 0; i < nb_sections; i++)
      if (section_name && (&sections[i]) && sections[i].section_name)
      if (strcmp (sections[i].section_name, section_name) == 0)
        return i;
    return PE_SECTION_INDEX_INVALID;
}


But still the same crash in strcmp(). 
   Could you try to check that section_name ansd sections array are valid...
It will probably require that you recompile GDB :(
Hi, today, I build gdb with "-O0 -g", here is the variables I see when it crashed.

Program received signal SIGSEGV, Segmentation fault.
0x77c47784 in strcmp () from C:\WINDOWS\system32\msvcrt.dll
(gdb) bt
#0  0x77c47784 in strcmp () from C:\WINDOWS\system32\msvcrt.dll
#1  0x00562eb9 in get_pe_section_index (section_name=0x5548638 ".data",
    sections=0x4b33b38, nb_sections=5) at ../../gdb/gdb/coff-pe-read.c:113
#2  0x00562f08 in get_section_vmas (abfd=0x4caede8, sectp=0x55496e8,
    context=0x285f5ec) at ../../gdb/gdb/coff-pe-read.c:134
#3  0x0064e7ee in bfd_map_over_sections (abfd=0x4caede8,
    operation=0x562ed5 <get_section_vmas>, user_storage=0x285f5ec)
    at ../../gdb/bfd/section.c:1329
#4  0x00563d2c in read_pe_exported_syms (objfile=0x5615090)
    at ../../gdb/gdb/coff-pe-read.c:525
#5  0x00560887 in coff_symtab_read (symtab_offset=0, nsyms=0,
    objfile=0x5615090) at ../../gdb/gdb/coffread.c:1127
#6  0x0055f660 in coff_symfile_read (objfile=0x5615090, symfile_flags=8)
    at ../../gdb/gdb/coffread.c:610
#7  0x004f1cc4 in read_symbols (objfile=0x5615090, add_flags=8)
    at ../../gdb/gdb/symfile.c:885
#8  0x004f203b in syms_from_objfile (objfile=0x5615090, addrs=0x2e04398,
    offsets=0x0, num_offsets=0, add_flags=8) at ../../gdb/gdb/symfile.c:1020
#9  0x004f2206 in symbol_file_add_with_addrs_or_offsets (abfd=0x4caede8,
    add_flags=8, addrs=0x2e04398, offsets=0x0, num_offsets=0, flags=2,
    parent=0x0) at ../../gdb/gdb/symfile.c:1123
#10 0x004f23bf in symbol_file_add_from_bfd (abfd=0x4caede8, add_flags=8,
    addrs=0x2e04398, flags=2, parent=0x0) at ../../gdb/gdb/symfile.c:1213
#11 0x0060ef33 in solib_read_symbols (so=0x4bdb6b0, flags=8)
    at ../../gdb/gdb/solib.c:608
#12 0x0060f50d in solib_add (pattern=0x0, from_tty=0,
    target=0x9ec6c0 <current_target>, readsyms=1) at ../../gdb/gdb/solib.c:919
#13 0x0050146f in post_create_inferior (target=0x9ec6c0 <current_target>,
    from_tty=0) at ../../gdb/gdb/infcmd.c:477
#14 0x0050175b in run_command_1 (args=0x0, from_tty=1, tbreak_at_main=0)
    at ../../gdb/gdb/infcmd.c:631
#15 0x005017b0 in run_command (args=0x0, from_tty=1)
    at ../../gdb/gdb/infcmd.c:645
#16 0x00447794 in do_cfunc (c=0x2d65ed0, args=0x0, from_tty=1)
    at ../../gdb/gdb/cli/cli-decode.c:114
#17 0x0044a0ce in cmd_func (cmd=0x2d65ed0, args=0x0, from_tty=1)
    at ../../gdb/gdb/cli/cli-decode.c:1859
#18 0x005f6ebf in execute_command (p=0x294321 "", from_tty=1)
    at ../../gdb/gdb/top.c:491
#19 0x00524cda in command_handler (command=0x294320 "")
    at ../../gdb/gdb/event-top.c:429
#20 0x0052524e in command_line_handler (rl=0x2e29fe0 "r")
    at ../../gdb/gdb/event-top.c:630
#21 0x00630133 in rl_callback_read_char ()
    at ../../gdb/readline/callback.c:220
#22 0x0052481f in rl_callback_read_char_wrapper (client_data=0x0)
    at ../../gdb/gdb/event-top.c:163
#23 0x00524c04 in stdin_event_handler (error=0, client_data=0x0)
    at ../../gdb/gdb/event-top.c:369
#24 0x00523df9 in handle_file_event (data=...)
    at ../../gdb/gdb/event-loop.c:827
#25 0x0052353d in process_event () at ../../gdb/gdb/event-loop.c:401
#26 0x00523602 in gdb_do_one_event () at ../../gdb/gdb/event-loop.c:465
#27 0x00523654 in start_event_loop () at ../../gdb/gdb/event-loop.c:490
#28 0x00524848 in cli_command_loop () at ../../gdb/gdb/event-top.c:176
#29 0x0051cdcf in current_interp_command_loop ()
    at ../../gdb/gdb/interps.c:332
#30 0x0051d6e9 in captured_command_loop (data=0x0) at ../../gdb/gdb/main.c:256
#31 0x0051be8c in catch_errors (func=0x51d6d4 <captured_command_loop>,
    func_args=0x0, errstring=0x7af593 <__PRETTY_FUNCTION__.13689+121> "",
    mask=6) at ../../gdb/gdb/exceptions.c:546
#32 0x0051e8c7 in captured_main (data=0x285fee0) at ../../gdb/gdb/main.c:1032
#33 0x0051be8c in catch_errors (func=0x51d923 <captured_main>,
    func_args=0x285fee0,
    errstring=0x7af593 <__PRETTY_FUNCTION__.13689+121> "", mask=6)
    at ../../gdb/gdb/exceptions.c:546
#34 0x0051e8fd in gdb_main (args=0x285fee0) at ../../gdb/gdb/main.c:1041
#35 0x00401737 in main (argc=1, argv=0x293ea0) at ../../gdb/gdb/gdb.c:34
(gdb) frame 1
#1  0x00562eb9 in get_pe_section_index (section_name=0x5548638 ".data",
    sections=0x4b33b38, nb_sections=5) at ../../gdb/gdb/coff-pe-read.c:113
113         if (strcmp (sections[i].section_name, section_name) == 0)
(gdb) p section_name
$1 = 0x5548638 ".data"
(gdb) p i
$2 = 2
(gdb) p sections[i].section_name
$3 = 0xabababab <Address 0xabababab out of bounds>
(gdb) print *sections@nb_sections
$4 = {{vma_offset = 2089811968, rva_start = 4096, rva_end = 515802,
    ms_type = mst_text, section_name = 0x7cd4a0 <coff_sym_fns+64> ".text"}, {
    vma_offset = 2868903936, rva_start = 2880154539, rva_end = 2880154539,
    ms_type = mst_unknown, section_name = 0x0}, {vma_offset = 393221,
    rva_start = 35784515, rva_end = 1920168494, ms_type = 2880110691,
    section_name = 0xabababab <Address 0xabababab out of bounds>}, {
    vma_offset = 0, rva_start = 536576, rva_end = 716408, ms_type = mst_data,
    section_name = 0x4b33b68 ".rsrc"}, {vma_offset = 0, rva_start = 716800,
    rva_end = 728800, ms_type = mst_data, section_name = 0x4b33be0 ".reloc"}}



Look, the value "0xabababab", I'm not sure why gdb report: out of bounds, where does this value come from?


Yuanhui Zhang

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