diff mbox

GDB internal error in pc_in_thread_step_range

Message ID 837eg4cick.fsf@gnu.org
State New, archived
Headers

Commit Message

Eli Zaretskii Dec. 20, 2018, 3:45 p.m. UTC 
  > Date: Wed, 19 Dec 2018 19:16:15 -0500
> From: Simon Marchi <simon.marchi@polymtl.ca>
> Cc: gdb-patches@sourceware.org
> 
> >   (top-gdb) p msymbol
> >   $3 = {minsym = 0x10450d38, objfile = 0x10443b48}
> >   (top-gdb) p msymbol.minsym.mginfo.name
> >   $4 = 0x104485cd "__register_frame_info"
> >   (top-gdb) p msymbol.minsym.mginfo
> >   $5 = {name = 0x104485cd "__register_frame_info", value = {ivalue = 0,
> >       block = 0x0, bytes = 0x0, address = 0x0, common_block = 0x0,
> >       chain = 0x0}, language_specific = {obstack = 0x0, demangled_name 
> > = 0x0},
> >     language = language_auto, ada_mangled = 0, section = 0}
> 
> Ok.  Well this is already strange.  Why is there an mst_text (code) 
> symbol with a value of 0?

Its address is zero because it's an unresolved symbol:

  d:\usr\eli>nm -A hello0.exe | fgrep " U "
  hello0.exe:         U ___deregister_frame_info
  hello0.exe:         U ___register_frame_info
  hello0.exe:         U __Jv_RegisterClasses

This symbol comes from a weak symbol defined in MinGW crtbegin.o:

  d:\usr\eli>nm -A lib/gcc/mingw32/6.3.0/crtbegin.o | fgrep _frame_info
  lib/gcc/mingw32/6.3.0/crtbegin.o:00000000 A .weak.___deregister_frame_info.___EH_FRAME_BEGIN__
  lib/gcc/mingw32/6.3.0/crtbegin.o:00000000 A .weak.___register_frame_info.___EH_FRAME_BEGIN__
  lib/gcc/mingw32/6.3.0/crtbegin.o:         w ___deregister_frame_info
  lib/gcc/mingw32/6.3.0/crtbegin.o:         w ___register_frame_info

> If your binary is anything like those I can 
> produce with x86_64-w64-mingw32-gcc (and it looks similar, given the 
> addresses you show), your "image base" is likely 0x400000, and "base of 
> code" 0x1000 (0x401000 in absolute).  I found this information using 
> "objdump -x", in the header somewhere.  I therefore expect all text 
> symbols to be >= 0x401000.  I would start digging why this text symbol 
> with a value of 0 exists.

See above.  But please note that I use mingw.org's MinGW, and my
executables are 32-bit, whereas you use MinGW64 and 64-bit
executables.  So some details might be different; in particular, I
don't think MinGW64 has this problematic symbol, because it's specific
to the DWARF2 exception unwinding implemented in libgcc, which 64-bit
Windows executables don't use.

> It would be interesting to look at some other symbols in the msymbols 
> vector.  Are the other mst_text symbols >= 0x401000?

There are 2 more unresolved mst_text symbols, see above; they all have
a zero address.  All the others are above 0x401000, indeed.

The lowest-address resolved minimal symbol whose type is mst_text is
this:

  (top-gdb) p msymbol[22]
  $112 = {mginfo = {name = 0x10447d95 "_mingw32_init_mainargs", value = {
	ivalue = 4199072, block = 0x4012a0 <_mingw32_init_mainargs>,
	bytes = 0x4012a0 <_mingw32_init_mainargs> "Æ\222?<\215D$,\307D$\004",
	address = 0x4012a0, common_block = 0x4012a0 <_mingw32_init_mainargs>,
	chain = 0x4012a0 <_mingw32_init_mainargs>}, language_specific = {
	obstack = 0x0, demangled_name = 0x0}, language = language_auto,
      ada_mangled = 0, section = 0}, size = 0, filename = 0x0, type = mst_text,
    created_by_gdb = 0, target_flag_1 = 0, target_flag_2 = 0, has_size = 0,
    hash_next = 0x0, demangled_hash_next = 0x0}

Interestingly, objdump shows this symbol in section 1:

  [  0](sec  1)(fl 0x00)(ty  20)(scl   2) (nx 0) 0x000002a0 __mingw32_init_mainargs

whereas the above minsym information shows section = 0.  Is this
expected?  If "real" symbols were to have section > 0, we could
perhaps reject the unresolved ones.

> Assuming this minimal symbol is wrong and assuming it wasn't there, then 
> I guess the search would fail and we would fall in the "Cannot find 
> bounds of current function" case of prepare_one_step?  That would be 
> appropriate in this case.

It's not wrong, but perhaps lookup_minimal_symbol_by_pc_section should
reject unresolved symbols for this purpose.  However, the question is
how?  One possibility is by their zero address.  (I don't see the weak
attribute, or any other indication of its being unresolved, in the
minimal symbol attributes.)

In any case, if we do call the "Cannot find bounds of current
function" error, that will throw to the command loop, which I think is
undesirable in this case.  We want GDB to step out of this code, not
to error out.

> Ok, from what I understand, all these "mst_abs" symbols do not represent 
> addresses.  They just represent numerical "values", like version 
> numbers, alignment sizes, etc.  So it seems right to skip them when 
> looking for the minimal symbol preceding pc.
> 
> It looks like minimal_symbol_upper_bound is buggy, in that it should not 
> consider these mst_abs.  If we are looking for the end of a memory 
> range, we should not consider those symbols that do not even represent 
> memory addresses...

Indeed, the following change is enough to avoid the internal error:

However, it still shows the incorrect function name from the
zero-address symbol:

  7       }
  (gdb) n
  0x00401288 in __register_frame_info ()
  (gdb) n
  Single stepping until exit from function __register_frame_info,
  which has no line number information.
  [Inferior 1 (process 10424) exited normally]

I think if we want to avoid showing __register_frame_info, we need
further changes in lookup_minimal_symbol_by_pc_section.  But I don't
see how this will help us, unless we also allow displaying the above
message for functions whose names we don't know, perhaps saying
something like

  Single stepping until exit from function <unknown>

> > That's what I did.  The problem seems to be that the low value of PC
> > doesn't allow GDB to find a reasonable symbol; what it finds are
> > symbols with very low addresses, which don't look like symbols
> > relevant to the issue at hand.  I see the same symbols and addresses
> > in the output of "objdump -t" (I can show it if you want).
> 
> If you could pastebin it, or send it as an attachment, I think it would 
> be useful.  Consider sending the output of "objdump -x", which I think 
> gives a superset of "objdump -t".

Attached.

> > Where do we go from here?
> 
> I would say
> 
> 1. investigate if the text symbol at address 0 really has business being 
> there.

Done.

> 2. investigate if there should be some text symbol that should really 
> contain 0x0040126d, that for some reason does not end up in GDB's 
> minimal symbol table.

The function in which the PC value of 0x401288 lives is
__mingw_CRTStartup, which ends like this:

  /* Call the main() function. If the user does not supply one
   * the one in the 'libmingw32.a' library will be linked in, and
   * that one calls WinMain().  See main.c in the 'lib' directory
   * for more details.
   */
  nRet = main (_argc, _argv, environ);

  /* Perform exit processing for the C library. This means flushing
   * output and calling atexit() registered functions.
   */
  _cexit ();

  ExitProcess (nRet);
}

This function is declared in the MinGW runtime sources as follows:

  static __MINGW_ATTRIB_NORETURN void __mingw_CRTStartup (void);

But its symbol is not in the symbol table.  Not sure why, perhaps
because it's a static function?  But the code is there, starting at
the address 0x4011b0.  The last part, after exiting 'main', which
corresponds to the above source snippet is this:

  (gdb) disassemble 0x401283,0x401294
  Dump of assembler code from 0x401283 to 0x401294:
     0x00401283 <__register_frame_info+4199043>:  call   0x401460 <main>
     0x00401288 <__register_frame_info+4199048>:  mov    %eax,%ebx
     0x0040128a <__register_frame_info+4199050>:  call   0x403a90 <_cexit>
     0x0040128f <__register_frame_info+4199055>:  mov    %ebx,(%esp)
     0x00401292 <__register_frame_info+4199058>:  call   0x403b28 <ExitProcess@4>

So when this problem happens, we are at the "mov %eax,%ebx"
instruction after exiting 'main', as I'd expect.
hello0.exe:     file format pei-i386
hello0.exe
architecture: i386, flags 0x0000013a:
EXEC_P, HAS_DEBUG, HAS_SYMS, HAS_LOCALS, D_PAGED
start address 0x004012e0

Characteristics 0x107
	relocations stripped
	executable
	line numbers stripped
	32 bit words

Time/Date		Sun Nov 18 09:35:52 2018
Magic			010b	(PE32)
MajorLinkerVersion	2
MinorLinkerVersion	31
SizeOfCode		00002c00
SizeOfInitializedData	00004600
SizeOfUninitializedData	00000200
AddressOfEntryPoint	000012e0
BaseOfCode		00001000
BaseOfData		00004000
ImageBase		00400000
SectionAlignment	00001000
FileAlignment		00000200
MajorOSystemVersion	4
MinorOSystemVersion	0
MajorImageVersion	1
MinorImageVersion	0
MajorSubsystemVersion	4
MinorSubsystemVersion	0
Win32Version		00000000
SizeOfImage		00015000
SizeOfHeaders		00000400
CheckSum		00011add
Subsystem		00000003	(Windows CUI)
DllCharacteristics	00000000
SizeOfStackReserve	00200000
SizeOfStackCommit	00001000
SizeOfHeapReserve	00100000
SizeOfHeapCommit	00001000
LoaderFlags		00000000
NumberOfRvaAndSizes	00000010

The Data Directory
Entry 0 00000000 00000000 Export Directory [.edata (or where ever we found it)]
Entry 1 00008000 000005bc Import Directory [parts of .idata]
Entry 2 00000000 00000000 Resource Directory [.rsrc]
Entry 3 00000000 00000000 Exception Directory [.pdata]
Entry 4 00000000 00000000 Security Directory
Entry 5 00000000 00000000 Base Relocation Directory [.reloc]
Entry 6 00000000 00000000 Debug Directory
Entry 7 00000000 00000000 Description Directory
Entry 8 00000000 00000000 Special Directory
Entry 9 0000a004 00000018 Thread Storage Directory [.tls]
Entry a 00000000 00000000 Load Configuration Directory
Entry b 00000000 00000000 Bound Import Directory
Entry c 00008128 000000d8 Import Address Table Directory
Entry d 00000000 00000000 Delay Import Directory
Entry e 00000000 00000000 CLR Runtime Header
Entry f 00000000 00000000 Reserved

There is an import table in .idata at 0x408000

The Import Tables (interpreted .idata section contents)
 vma:            Hint    Time      Forward  DLL       First
                 Table   Stamp     Chain    Name      Thunk
 00008000	00008050 00000000 00000000 00008510 00008128

	DLL Name: KERNEL32.dll
	vma:  Hint/Ord Member-Name Bound-To
	8200	  208  DeleteCriticalSection
	8218	  237  EnterCriticalSection
	8230	  280  ExitProcess
	823e	  301  FindClose
	824a	  305  FindFirstFileA
	825c	  322  FindNextFileA
	826c	  353  FreeLibrary
	827a	  389  GetCommandLineA
	828c	  511  GetLastError
	829c	  530  GetModuleHandleA
	82b0	  578  GetProcAddress
	82c2	  735  InitializeCriticalSection
	82de	  815  LeaveCriticalSection
	82f6	  818  LoadLibraryA
	8306	 1141  SetUnhandledExceptionFilter
	8324	 1174  TlsGetValue
	8332	 1214  VirtualProtect
	8344	 1216  VirtualQuery

 00008014	0000809c 00000000 00000000 00008528 00008174

	DLL Name: msvcrt.dll
	vma:  Hint/Ord Member-Name Bound-To
	8354	   80  _strdup
	835e	   82  _stricoll

 00008028	000080a8 00000000 00000000 000085b0 00008180

	DLL Name: msvcrt.dll
	vma:  Hint/Ord Member-Name Bound-To
	836a	   89  __getmainargs
	837a	  120  __mb_cur_max
	838a	  132  __p__environ
	839a	  134  __p__fmode
	83a8	  154  __set_app_type
	83ba	  220  _cexit
	83c4	  286  _errno
	83ce	  325  _fpreset
	83da	  351  _fullpath
	83e6	  418  _iob
	83ee	  423  _isctype
	83fa	  690  _onexit
	8404	  699  _pctype
	840e	  754  _setmode
	841a	 1084  abort
	8422	 1092  atexit
	842c	 1099  calloc
	8436	 1132  free
	843e	 1143  fwrite
	8448	 1188  malloc
	8452	 1195  mbstowcs
	845e	 1200  memcpy
	8468	 1213  puts
	8470	 1221  realloc
	847a	 1228  setlocale
	8486	 1230  signal
	8490	 1243  strcoll
	849a	 1250  strlen
	84a4	 1278  tolower
	84ae	 1285  vfprintf
	84ba	 1326  wcstombs

 0000803c	00000000 00000000 00000000 00000000 00000000

Sections:
Idx Name          Size      VMA       LMA       File off  Algn
  0 .text         00002b74  00401000  00401000  00000400  2**4
                  CONTENTS, ALLOC, LOAD, READONLY, CODE, DATA
  1 .data         0000001c  00404000  00404000  00003000  2**2
                  CONTENTS, ALLOC, LOAD, DATA
  2 .rdata        000002fc  00405000  00405000  00003200  2**2
                  CONTENTS, ALLOC, LOAD, READONLY, DATA
  3 .eh_frame     0000099c  00406000  00406000  00003600  2**2
                  CONTENTS, ALLOC, LOAD, READONLY, DATA
  4 .bss          00000070  00407000  00407000  00000000  2**2
                  ALLOC
  5 .idata        000005bc  00408000  00408000  00004000  2**2
                  CONTENTS, ALLOC, LOAD, DATA
  6 .CRT          00000018  00409000  00409000  00004600  2**2
                  CONTENTS, ALLOC, LOAD, DATA
  7 .tls          00000020  0040a000  0040a000  00004800  2**2
                  CONTENTS, ALLOC, LOAD, DATA
  8 .debug_aranges 00000058  0040b000  0040b000  00004a00  2**3
                  CONTENTS, READONLY, DEBUGGING
  9 .debug_info   00001e7f  0040c000  0040c000  00004c00  2**0
                  CONTENTS, READONLY, DEBUGGING
 10 .debug_abbrev 000001be  0040e000  0040e000  00006c00  2**0
                  CONTENTS, READONLY, DEBUGGING
 11 .debug_line   000002b8  0040f000  0040f000  00006e00  2**0
                  CONTENTS, READONLY, DEBUGGING
 12 .debug_frame  00000038  00410000  00410000  00007200  2**2
                  CONTENTS, READONLY, DEBUGGING
 13 .debug_macro  00003f1d  00411000  00411000  00007400  2**0
                  CONTENTS, READONLY, DEBUGGING
SYMBOL TABLE:
[  0](sec  1)(fl 0x00)(ty  20)(scl   2) (nx 0) 0x000002a0 __mingw32_init_mainargs
[  1](sec  1)(fl 0x00)(ty  20)(scl   2) (nx 0) 0x000002e0 _mainCRTStartup
[  2](sec  1)(fl 0x00)(ty  20)(scl   2) (nx 0) 0x00000300 _WinMainCRTStartup
[  3](sec  1)(fl 0x00)(ty  20)(scl   2) (nx 0) 0x00000320 _atexit
[  4](sec  1)(fl 0x00)(ty  20)(scl   2) (nx 0) 0x00000330 __onexit
[  5](sec  1)(fl 0x00)(ty   0)(scl   3) (nx 1) 0x00000000 .text
AUX scnlen 0x336 nreloc 42 nlnno 0
[  7](sec  5)(fl 0x00)(ty   0)(scl   3) (nx 1) 0x00000000 .bss
AUX scnlen 0x8 nreloc 0 nlnno 0
[  9](sec -2)(fl 0x00)(ty   0)(scl 103) (nx 1) 0x0000001e cygming-crtbegin.c
File 
[ 11](sec  5)(fl 0x00)(ty   0)(scl   3) (nx 0) 0x00000008 _obj
[ 12](sec  2)(fl 0x00)(ty   0)(scl   3) (nx 0) 0x00000000 _deregister_frame_fn
[ 13](sec  2)(fl 0x00)(ty   0)(scl   3) (nx 0) 0x00000018 ___JCR_LIST__
[ 14](sec  1)(fl 0x00)(ty  20)(scl   2) (nx 1) 0x00000340 ___gcc_register_frame
AUX tagndx 0 ttlsiz 0x0 lnnos 0 next 0
[ 16](sec  1)(fl 0x00)(ty  20)(scl   2) (nx 0) 0x00000430 ___gcc_deregister_frame
[ 17](sec  1)(fl 0x00)(ty   0)(scl   3) (nx 1) 0x00000340 .text
AUX scnlen 0x11e nreloc 28 nlnno 0
[ 19](sec  2)(fl 0x00)(ty   0)(scl   3) (nx 1) 0x00000000 .data
AUX scnlen 0x4 nreloc 0 nlnno 0
[ 21](sec  5)(fl 0x00)(ty   0)(scl   3) (nx 1) 0x00000008 .bss
AUX scnlen 0x18 nreloc 0 nlnno 0
[ 23](sec  4)(fl 0x00)(ty   0)(scl   3) (nx 1) 0x000000b8 .eh_frame
AUX scnlen 0x64 nreloc 2 nlnno 0
[ 25](sec  3)(fl 0x00)(ty   0)(scl   3) (nx 1) 0x00000000 .rdata
AUX scnlen 0x63 nreloc 0 nlnno 0
[ 27](sec  3)(fl 0x00)(ty   0)(scl   3) (nx 1) 0x0000015c .rdata$zzz
AUX scnlen 0x11 nreloc 0 nlnno 0
[ 29](sec  2)(fl 0x00)(ty   0)(scl   3) (nx 0) 0x00000018 .jcr
[ 30](sec -2)(fl 0x00)(ty   0)(scl 103) (nx 1) 0x0000006a hello.c
File 
[ 32](sec  1)(fl 0x00)(ty  20)(scl   2) (nx 1) 0x00000460 _main
AUX tagndx 0 ttlsiz 0x0 lnnos 0 next 0
[ 34](sec  1)(fl 0x00)(ty   0)(scl   3) (nx 1) 0x00000460 .text
AUX scnlen 0x21 nreloc 3 nlnno 0
[ 36](sec  2)(fl 0x00)(ty   0)(scl   3) (nx 1) 0x00000004 .data
AUX scnlen 0x0 nreloc 0 nlnno 0
[ 38](sec  5)(fl 0x00)(ty   0)(scl   3) (nx 1) 0x00000020 .bss
AUX scnlen 0x0 nreloc 0 nlnno 0
[ 40](sec  3)(fl 0x00)(ty   0)(scl   3) (nx 1) 0x00000064 .rdata
AUX scnlen 0x18 nreloc 0 nlnno 0
[ 42](sec 10)(fl 0x00)(ty   0)(scl   3) (nx 1) 0x00000000 .debug_info
AUX scnlen 0x180 nreloc 5 nlnno 0
[ 44](sec 11)(fl 0x00)(ty   0)(scl   3) (nx 1) 0x00000000 .debug_abbrev
AUX scnlen 0x8f nreloc 0 nlnno 0
[ 46](sec  9)(fl 0x00)(ty   0)(scl   3) (nx 1) 0x00000000 .debug_aranges
AUX scnlen 0x20 nreloc 2 nlnno 0
[ 48](sec 14)(fl 0x00)(ty   0)(scl   3) (nx 1) 0x00000000 .debug_macro
AUX scnlen 0x3f1d nreloc 1 nlnno 0
[ 50](sec 12)(fl 0x00)(ty   0)(scl   3) (nx 1) 0x00000000 .debug_line
AUX scnlen 0xf0 nreloc 1 nlnno 0
[ 52](sec  3)(fl 0x00)(ty   0)(scl   3) (nx 1) 0x00000170 .rdata$zzz
AUX scnlen 0x23 nreloc 0 nlnno 0
[ 54](sec  4)(fl 0x00)(ty   0)(scl   3) (nx 1) 0x0000011c .eh_frame
AUX scnlen 0x38 nreloc 1 nlnno 0
[ 56](sec  1)(fl 0x00)(ty  20)(scl   2) (nx 1) 0x00000490 __setargv
AUX tagndx 0 ttlsiz 0x0 lnnos 0 next 0
[ 58](sec  1)(fl 0x00)(ty   0)(scl   3) (nx 1) 0x00000490 .text
AUX scnlen 0x39f nreloc 15 nlnno 0
[ 60](sec  1)(fl 0x00)(ty  20)(scl   2) (nx 1) 0x00000830 ___cpu_features_init
AUX tagndx 0 ttlsiz 0x0 lnnos 0 next 0
[ 62](sec  1)(fl 0x00)(ty   0)(scl   3) (nx 1) 0x00000830 .text
AUX scnlen 0xdc nreloc 10 nlnno 0
[ 64](sec  5)(fl 0x00)(ty   0)(scl   3) (nx 1) 0x00000024 .bss
AUX scnlen 0x4 nreloc 0 nlnno 0
[ 66](sec  1)(fl 0x00)(ty  20)(scl   2) (nx 1) 0x00000910 ___do_global_dtors
AUX tagndx 0 ttlsiz 0x0 lnnos 0 next 0
[ 68](sec  1)(fl 0x00)(ty  20)(scl   2) (nx 0) 0x00000940 ___do_global_ctors
[ 69](sec  1)(fl 0x00)(ty  20)(scl   2) (nx 0) 0x00000990 ___main
[ 70](sec  1)(fl 0x00)(ty   0)(scl   3) (nx 1) 0x00000910 .text
AUX scnlen 0x9c nreloc 10 nlnno 0
[ 72](sec  2)(fl 0x00)(ty   0)(scl   3) (nx 1) 0x00000010 .data
AUX scnlen 0x4 nreloc 1 nlnno 0
[ 74](sec  5)(fl 0x00)(ty   0)(scl   3) (nx 1) 0x00000028 .bss
AUX scnlen 0x4 nreloc 0 nlnno 0
[ 76](sec  1)(fl 0x00)(ty  20)(scl   2) (nx 0) 0x00000a00 ___dyn_tls_init@12
[ 77](sec  1)(fl 0x00)(ty  20)(scl   2) (nx 0) 0x00000a90 ___tlregdtor
[ 78](sec  1)(fl 0x00)(ty   0)(scl   3) (nx 1) 0x000009b0 .text
AUX scnlen 0xe3 nreloc 7 nlnno 0
[ 80](sec  5)(fl 0x00)(ty   0)(scl   3) (nx 1) 0x0000002c .bss
AUX scnlen 0x10 nreloc 0 nlnno 0
[ 82](sec  7)(fl 0x00)(ty   0)(scl   3) (nx 1) 0x00000014 .CRT$XDZ
AUX scnlen 0x4 nreloc 0 nlnno 0
[ 84](sec  7)(fl 0x00)(ty   0)(scl   3) (nx 1) 0x00000010 .CRT$XDA
AUX scnlen 0x4 nreloc 0 nlnno 0
[ 86](sec  7)(fl 0x00)(ty   0)(scl   3) (nx 1) 0x00000000 .CRT$XLA
AUX scnlen 0x4 nreloc 0 nlnno 0
[ 88](sec  8)(fl 0x00)(ty   0)(scl   3) (nx 1) 0x0000001c .tls$ZZZ
AUX scnlen 0x1 nreloc 0 nlnno 0
[ 90](sec  8)(fl 0x00)(ty   0)(scl   3) (nx 1) 0x00000000 .tls$AAA
AUX scnlen 0x1 nreloc 0 nlnno 0
[ 92](sec  1)(fl 0x00)(ty  20)(scl   2) (nx 0) 0x00000b00 ____w64_mingwthr_add_key_dtor
[ 93](sec  1)(fl 0x00)(ty  20)(scl   2) (nx 0) 0x00000b90 ____w64_mingwthr_remove_key_dtor
[ 94](sec  1)(fl 0x00)(ty  20)(scl   2) (nx 0) 0x00000c30 ___mingw_TLScallback
[ 95](sec  1)(fl 0x00)(ty   0)(scl   3) (nx 1) 0x00000aa0 .text
AUX scnlen 0x227 nreloc 35 nlnno 0
[ 97](sec  5)(fl 0x00)(ty   0)(scl   3) (nx 1) 0x0000003c .bss
AUX scnlen 0x20 nreloc 0 nlnno 0
[ 99](sec  1)(fl 0x00)(ty  20)(scl   2) (nx 0) 0x00000e10 __pei386_runtime_relocator
[100](sec  1)(fl 0x00)(ty   0)(scl   3) (nx 1) 0x00000cd0 .text
AUX scnlen 0x30b nreloc 33 nlnno 0
[102](sec  5)(fl 0x00)(ty   0)(scl   3) (nx 1) 0x0000005c .bss
AUX scnlen 0x4 nreloc 0 nlnno 0
[104](sec  3)(fl 0x00)(ty   0)(scl   3) (nx 1) 0x00000080 .rdata
AUX scnlen 0xaa nreloc 0 nlnno 0
[106](sec -2)(fl 0x00)(ty   0)(scl 103) (nx 1) 0x0000007c fake
File 
[108](sec 10)(fl 0x00)(ty   0)(scl   3) (nx 1) 0x00000180 .debug_info
AUX scnlen 0xa7 nreloc 4 nlnno 0
[110](sec 11)(fl 0x00)(ty   0)(scl   3) (nx 1) 0x0000008f .debug_abbrev
AUX scnlen 0x14 nreloc 0 nlnno 0
[112](sec 12)(fl 0x00)(ty   0)(scl   3) (nx 1) 0x000000f0 .debug_line
AUX scnlen 0x71 nreloc 1 nlnno 0
[114](sec  1)(fl 0x00)(ty   0)(scl   3) (nx 1) 0x00000fe0 .text
AUX scnlen 0x2a nreloc 0 nlnno 0
[116](sec  2)(fl 0x00)(ty   0)(scl   3) (nx 1) 0x00000014 .data
AUX scnlen 0x0 nreloc 0 nlnno 0
[118](sec  5)(fl 0x00)(ty   0)(scl   3) (nx 1) 0x00000068 .bss
AUX scnlen 0x0 nreloc 0 nlnno 0
[120](sec  9)(fl 0x00)(ty   0)(scl   3) (nx 1) 0x00000020 .debug_aranges
AUX scnlen 0x20 nreloc 2 nlnno 0
[122](sec 13)(fl 0x00)(ty   0)(scl   3) (nx 1) 0x00000000 .debug_frame
AUX scnlen 0x38 nreloc 2 nlnno 0
[124](sec -2)(fl 0x00)(ty   0)(scl 103) (nx 1) 0x0000010d libgcc2.c
File 
[126](sec  1)(fl 0x00)(ty   0)(scl   3) (nx 1) 0x0000100c .text
AUX scnlen 0x0 nreloc 0 nlnno 0
[128](sec  2)(fl 0x00)(ty   0)(scl   3) (nx 1) 0x00000014 .data
AUX scnlen 0x0 nreloc 0 nlnno 0
[130](sec  5)(fl 0x00)(ty   0)(scl   3) (nx 1) 0x00000068 .bss
AUX scnlen 0x0 nreloc 0 nlnno 0
[132](sec 10)(fl 0x00)(ty   0)(scl   3) (nx 1) 0x00000227 .debug_info
AUX scnlen 0x1c58 nreloc 4 nlnno 0
[134](sec 11)(fl 0x00)(ty   0)(scl   3) (nx 1) 0x000000a3 .debug_abbrev
AUX scnlen 0x11b nreloc 0 nlnno 0
[136](sec  9)(fl 0x00)(ty   0)(scl   3) (nx 1) 0x00000040 .debug_aranges
AUX scnlen 0x18 nreloc 1 nlnno 0
[138](sec 12)(fl 0x00)(ty   0)(scl   3) (nx 1) 0x00000161 .debug_line
AUX scnlen 0x157 nreloc 0 nlnno 0
[140](sec  3)(fl 0x00)(ty   0)(scl   3) (nx 1) 0x00000284 .rdata$zzz
AUX scnlen 0x11 nreloc 0 nlnno 0
[142](sec  1)(fl 0x00)(ty  20)(scl   2) (nx 1) 0x00001010 _fesetenv
AUX tagndx 0 ttlsiz 0x0 lnnos 0 next 0
[144](sec  1)(fl 0x00)(ty   0)(scl   3) (nx 1) 0x00001010 .text
AUX scnlen 0x6c nreloc 5 nlnno 0
[146](sec  2)(fl 0x00)(ty   0)(scl   3) (nx 1) 0x00000014 .data
AUX scnlen 0x4 nreloc 0 nlnno 0
[148](sec  1)(fl 0x00)(ty  20)(scl   2) (nx 0) 0x00001fb0 ___mingw_glob
[149](sec  1)(fl 0x00)(ty  20)(scl   2) (nx 0) 0x000020a0 ___mingw_globfree
[150](sec  1)(fl 0x00)(ty   0)(scl   3) (nx 1) 0x00001080 .text
AUX scnlen 0x107f nreloc 52 nlnno 0
[152](sec  3)(fl 0x00)(ty   0)(scl   3) (nx 1) 0x0000012c .rdata
AUX scnlen 0x13 nreloc 0 nlnno 0
[154](sec  1)(fl 0x00)(ty  20)(scl   2) (nx 1) 0x00002100 ___mingw_dirname
AUX tagndx 0 ttlsiz 0x0 lnnos 0 next 0
[156](sec  1)(fl 0x00)(ty   0)(scl   3) (nx 1) 0x00002100 .text
AUX scnlen 0x3f4 nreloc 27 nlnno 0
[158](sec  5)(fl 0x00)(ty   0)(scl   3) (nx 1) 0x00000068 .bss
AUX scnlen 0x4 nreloc 0 nlnno 0
[160](sec  3)(fl 0x00)(ty   0)(scl   3) (nx 1) 0x00000140 .rdata
AUX scnlen 0x6 nreloc 0 nlnno 0
[162](sec  1)(fl 0x00)(ty  20)(scl   2) (nx 0) 0x00002680 ___mingw_opendir
[163](sec  1)(fl 0x00)(ty  20)(scl   2) (nx 0) 0x00002840 ___mingw_readdir
[164](sec  1)(fl 0x00)(ty  20)(scl   2) (nx 0) 0x00002890 ___mingw_closedir
[165](sec  1)(fl 0x00)(ty  20)(scl   2) (nx 0) 0x000028e0 ___mingw_rewinddir
[166](sec  1)(fl 0x00)(ty  20)(scl   2) (nx 0) 0x00002940 ___mingw_telldir
[167](sec  1)(fl 0x00)(ty  20)(scl   2) (nx 0) 0x00002970 ___mingw_seekdir
[168](sec  1)(fl 0x00)(ty   0)(scl   3) (nx 1) 0x00002500 .text
AUX scnlen 0x4e1 nreloc 26 nlnno 0
[170](sec  6)(fl 0x00)(ty   0)(scl   3) (nx 0) 0x000001f8 .idata$5
[171](sec  6)(fl 0x00)(ty   0)(scl   3) (nx 0) 0x000004ba .idata$6
[172](sec  6)(fl 0x00)(ty   0)(scl   3) (nx 0) 0x000001f4 .idata$5
[173](sec  6)(fl 0x00)(ty   0)(scl   3) (nx 0) 0x000004ae .idata$6
[174](sec  6)(fl 0x00)(ty   0)(scl   3) (nx 0) 0x000001f0 .idata$5
[175](sec  6)(fl 0x00)(ty   0)(scl   3) (nx 0) 0x000004a4 .idata$6
[176](sec  6)(fl 0x00)(ty   0)(scl   3) (nx 0) 0x000001ec .idata$5
[177](sec  6)(fl 0x00)(ty   0)(scl   3) (nx 0) 0x0000049a .idata$6
[178](sec  6)(fl 0x00)(ty   0)(scl   3) (nx 0) 0x000001e8 .idata$5
[179](sec  6)(fl 0x00)(ty   0)(scl   3) (nx 0) 0x00000490 .idata$6
[180](sec  6)(fl 0x00)(ty   0)(scl   3) (nx 0) 0x000001e4 .idata$5
[181](sec  6)(fl 0x00)(ty   0)(scl   3) (nx 0) 0x00000486 .idata$6
[182](sec  6)(fl 0x00)(ty   0)(scl   3) (nx 0) 0x000001e0 .idata$5
[183](sec  6)(fl 0x00)(ty   0)(scl   3) (nx 0) 0x0000047a .idata$6
[184](sec  6)(fl 0x00)(ty   0)(scl   3) (nx 0) 0x000001dc .idata$5
[185](sec  6)(fl 0x00)(ty   0)(scl   3) (nx 0) 0x00000470 .idata$6
[186](sec  6)(fl 0x00)(ty   0)(scl   3) (nx 0) 0x000001d8 .idata$5
[187](sec  6)(fl 0x00)(ty   0)(scl   3) (nx 0) 0x00000468 .idata$6
[188](sec  6)(fl 0x00)(ty   0)(scl   3) (nx 0) 0x000001d4 .idata$5
[189](sec  6)(fl 0x00)(ty   0)(scl   3) (nx 0) 0x0000045e .idata$6
[190](sec  6)(fl 0x00)(ty   0)(scl   3) (nx 0) 0x000001d0 .idata$5
[191](sec  6)(fl 0x00)(ty   0)(scl   3) (nx 0) 0x00000452 .idata$6
[192](sec  6)(fl 0x00)(ty   0)(scl   3) (nx 0) 0x000001cc .idata$5
[193](sec  6)(fl 0x00)(ty   0)(scl   3) (nx 0) 0x00000448 .idata$6
[194](sec  6)(fl 0x00)(ty   0)(scl   3) (nx 0) 0x000001c8 .idata$5
[195](sec  6)(fl 0x00)(ty   0)(scl   3) (nx 0) 0x0000043e .idata$6
[196](sec  6)(fl 0x00)(ty   0)(scl   3) (nx 0) 0x000001c4 .idata$5
[197](sec  6)(fl 0x00)(ty   0)(scl   3) (nx 0) 0x00000436 .idata$6
[198](sec  6)(fl 0x00)(ty   0)(scl   3) (nx 0) 0x000001c0 .idata$5
[199](sec  6)(fl 0x00)(ty   0)(scl   3) (nx 0) 0x0000042c .idata$6
[200](sec  6)(fl 0x00)(ty   0)(scl   3) (nx 0) 0x00000422 .idata$6
[201](sec  6)(fl 0x00)(ty   0)(scl   3) (nx 0) 0x000001b8 .idata$5
[202](sec  6)(fl 0x00)(ty   0)(scl   3) (nx 0) 0x0000041a .idata$6
[203](sec  6)(fl 0x00)(ty   0)(scl   3) (nx 0) 0x000001b4 .idata$5
[204](sec  6)(fl 0x00)(ty   0)(scl   3) (nx 0) 0x0000040e .idata$6
[205](sec  6)(fl 0x00)(ty   0)(scl   3) (nx 0) 0x00000404 .idata$6
[206](sec  6)(fl 0x00)(ty   0)(scl   3) (nx 0) 0x000003fa .idata$6
[207](sec  6)(fl 0x00)(ty   0)(scl   3) (nx 0) 0x000001a8 .idata$5
[208](sec  6)(fl 0x00)(ty   0)(scl   3) (nx 0) 0x000003ee .idata$6
[209](sec  6)(fl 0x00)(ty   0)(scl   3) (nx 0) 0x000003e6 .idata$6
[210](sec  6)(fl 0x00)(ty   0)(scl   3) (nx 0) 0x000001a0 .idata$5
[211](sec  6)(fl 0x00)(ty   0)(scl   3) (nx 0) 0x000003da .idata$6
[212](sec  6)(fl 0x00)(ty   0)(scl   3) (nx 0) 0x00000198 .idata$5
[213](sec  6)(fl 0x00)(ty   0)(scl   3) (nx 0) 0x000003c4 .idata$6
[214](sec  6)(fl 0x00)(ty   0)(scl   3) (nx 0) 0x00000194 .idata$5
[215](sec  6)(fl 0x00)(ty   0)(scl   3) (nx 0) 0x000003ba .idata$6
[216](sec  6)(fl 0x00)(ty   0)(scl   3) (nx 0) 0x0000018c .idata$5
[217](sec  6)(fl 0x00)(ty   0)(scl   3) (nx 0) 0x0000039a .idata$6
[218](sec  6)(fl 0x00)(ty   0)(scl   3) (nx 0) 0x00000188 .idata$5
[219](sec  6)(fl 0x00)(ty   0)(scl   3) (nx 0) 0x0000038a .idata$6
[220](sec  6)(fl 0x00)(ty   0)(scl   3) (nx 0) 0x0000037a .idata$6
[221](sec  6)(fl 0x00)(ty   0)(scl   3) (nx 0) 0x00000180 .idata$5
[222](sec  6)(fl 0x00)(ty   0)(scl   3) (nx 0) 0x0000036a .idata$6
[223](sec  6)(fl 0x00)(ty   0)(scl   3) (nx 0) 0x000000a8 .idata$4
[224](sec  6)(fl 0x00)(ty   0)(scl   3) (nx 0) 0x00000180 .idata$5
[225](sec  6)(fl 0x00)(ty   0)(scl   3) (nx 0) 0x0000016c .idata$5
[226](sec  6)(fl 0x00)(ty   0)(scl   3) (nx 0) 0x00000344 .idata$6
[227](sec  6)(fl 0x00)(ty   0)(scl   3) (nx 0) 0x00000168 .idata$5
[228](sec  6)(fl 0x00)(ty   0)(scl   3) (nx 0) 0x00000332 .idata$6
[229](sec  6)(fl 0x00)(ty   0)(scl   3) (nx 0) 0x00000164 .idata$5
[230](sec  6)(fl 0x00)(ty   0)(scl   3) (nx 0) 0x00000324 .idata$6
[231](sec  6)(fl 0x00)(ty   0)(scl   3) (nx 0) 0x00000160 .idata$5
[232](sec  6)(fl 0x00)(ty   0)(scl   3) (nx 0) 0x00000306 .idata$6
[233](sec  6)(fl 0x00)(ty   0)(scl   3) (nx 0) 0x0000015c .idata$5
[234](sec  6)(fl 0x00)(ty   0)(scl   3) (nx 0) 0x000002f6 .idata$6
[235](sec  6)(fl 0x00)(ty   0)(scl   3) (nx 0) 0x00000158 .idata$5
[236](sec  6)(fl 0x00)(ty   0)(scl   3) (nx 0) 0x000002de .idata$6
[237](sec  6)(fl 0x00)(ty   0)(scl   3) (nx 0) 0x00000154 .idata$5
[238](sec  6)(fl 0x00)(ty   0)(scl   3) (nx 0) 0x000002c2 .idata$6
[239](sec  6)(fl 0x00)(ty   0)(scl   3) (nx 0) 0x00000150 .idata$5
[240](sec  6)(fl 0x00)(ty   0)(scl   3) (nx 0) 0x000002b0 .idata$6
[241](sec  6)(fl 0x00)(ty   0)(scl   3) (nx 0) 0x0000014c .idata$5
[242](sec  6)(fl 0x00)(ty   0)(scl   3) (nx 0) 0x0000029c .idata$6
[243](sec  6)(fl 0x00)(ty   0)(scl   3) (nx 0) 0x00000148 .idata$5
[244](sec  6)(fl 0x00)(ty   0)(scl   3) (nx 0) 0x0000028c .idata$6
[245](sec  6)(fl 0x00)(ty   0)(scl   3) (nx 0) 0x00000144 .idata$5
[246](sec  6)(fl 0x00)(ty   0)(scl   3) (nx 0) 0x0000027a .idata$6
[247](sec  6)(fl 0x00)(ty   0)(scl   3) (nx 0) 0x00000140 .idata$5
[248](sec  6)(fl 0x00)(ty   0)(scl   3) (nx 0) 0x0000026c .idata$6
[249](sec  6)(fl 0x00)(ty   0)(scl   3) (nx 0) 0x0000013c .idata$5
[250](sec  6)(fl 0x00)(ty   0)(scl   3) (nx 0) 0x0000025c .idata$6
[251](sec  6)(fl 0x00)(ty   0)(scl   3) (nx 0) 0x00000138 .idata$5
[252](sec  6)(fl 0x00)(ty   0)(scl   3) (nx 0) 0x0000024a .idata$6
[253](sec  6)(fl 0x00)(ty   0)(scl   3) (nx 0) 0x00000134 .idata$5
[254](sec  6)(fl 0x00)(ty   0)(scl   3) (nx 0) 0x0000023e .idata$6
[255](sec  6)(fl 0x00)(ty   0)(scl   3) (nx 0) 0x00000130 .idata$5
[256](sec  6)(fl 0x00)(ty   0)(scl   3) (nx 0) 0x00000230 .idata$6
[257](sec  6)(fl 0x00)(ty   0)(scl   3) (nx 0) 0x0000012c .idata$5
[258](sec  6)(fl 0x00)(ty   0)(scl   3) (nx 0) 0x00000218 .idata$6
[259](sec  6)(fl 0x00)(ty   0)(scl   3) (nx 0) 0x00000128 .idata$5
[260](sec  6)(fl 0x00)(ty   0)(scl   3) (nx 0) 0x00000200 .idata$6
[261](sec  6)(fl 0x00)(ty   0)(scl   3) (nx 0) 0x00000050 .idata$4
[262](sec  6)(fl 0x00)(ty   0)(scl   3) (nx 0) 0x00000128 .idata$5
[263](sec  6)(fl 0x00)(ty   0)(scl   3) (nx 0) 0x00000178 .idata$5
[264](sec  6)(fl 0x00)(ty   0)(scl   3) (nx 0) 0x0000035e .idata$6
[265](sec  6)(fl 0x00)(ty   0)(scl   3) (nx 0) 0x00000174 .idata$5
[266](sec  6)(fl 0x00)(ty   0)(scl   3) (nx 0) 0x00000354 .idata$6
[267](sec  6)(fl 0x00)(ty   0)(scl   3) (nx 0) 0x0000009c .idata$4
[268](sec  6)(fl 0x00)(ty   0)(scl   3) (nx 0) 0x00000174 .idata$5
[269](sec -2)(fl 0x00)(ty   0)(scl 103) (nx 1) 0x00000127 cygming-crtend.c
File 
[271](sec  4)(fl 0x00)(ty   0)(scl   3) (nx 0) 0x00000960 ___FRAME_END__
[272](sec  2)(fl 0x00)(ty   0)(scl   3) (nx 0) 0x00000018 ___JCR_END__
[273](sec  1)(fl 0x00)(ty  20)(scl   3) (nx 1) 0x00002b50 _register_frame_ctor
AUX tagndx 0 ttlsiz 0x0 lnnos 0 next 0
[275](sec  1)(fl 0x00)(ty   0)(scl   3) (nx 1) 0x00002b50 .text
AUX scnlen 0x0 nreloc 0 nlnno 0
[277](sec  2)(fl 0x00)(ty   0)(scl   3) (nx 1) 0x00000018 .data
AUX scnlen 0x0 nreloc 0 nlnno 0
[279](sec  5)(fl 0x00)(ty   0)(scl   3) (nx 1) 0x0000006c .bss
AUX scnlen 0x0 nreloc 0 nlnno 0
[281](sec  4)(fl 0x00)(ty   0)(scl   3) (nx 1) 0x00000960 .eh_frame
AUX scnlen 0x3c nreloc 1 nlnno 0
[283](sec  2)(fl 0x00)(ty   0)(scl   3) (nx 1) 0x00000018 .jcr
AUX scnlen 0x4 nreloc 0 nlnno 0
[285](sec  1)(fl 0x00)(ty   0)(scl   3) (nx 1) 0x00002b50 .text.startup
AUX scnlen 0x9 nreloc 1 nlnno 0
[287](sec  1)(fl 0x00)(ty   0)(scl   3) (nx 1) 0x00002b64 .ctors.65535
AUX scnlen 0x4 nreloc 1 nlnno 0
[289](sec  3)(fl 0x00)(ty   0)(scl   3) (nx 1) 0x000002e8 .rdata$zzz
AUX scnlen 0x11 nreloc 0 nlnno 0
[291](sec  6)(fl 0x00)(ty   0)(scl   3) (nx 0) 0x0000019c .idata$5
[292](sec  6)(fl 0x00)(ty   0)(scl   3) (nx 0) 0x000003ce .idata$6
[293](sec  6)(fl 0x00)(ty   0)(scl   3) (nx 0) 0x00000190 .idata$5
[294](sec  6)(fl 0x00)(ty   0)(scl   3) (nx 0) 0x000003a8 .idata$6
[295](sec  6)(fl 0x00)(ty   0)(scl   2) (nx 0) 0x00000138 __imp__FindFirstFileA@8
[296](sec  1)(fl 0x00)(ty  20)(scl   2) (nx 0) 0x00002a90 __cexit
[297](sec  1)(fl 0x00)(ty  20)(scl   2) (nx 0) 0x00002ab8 _VirtualProtect@16
[298](sec  3)(fl 0x00)(ty   0)(scl   2) (nx 0) 0x000002fc ___RUNTIME_PSEUDO_RELOC_LIST__
[299](sec  6)(fl 0x00)(ty   0)(scl   2) (nx 0) 0x000001a0 __imp___fullpath
[300](sec  1)(fl 0x00)(ty  20)(scl   2) (nx 0) 0x00002b18 _FindFirstFileA@8
[301](sec  6)(fl 0x00)(ty   0)(scl   2) (nx 0) 0x000001b4 __imp___setmode
[302](sec  2)(fl 0x00)(ty   0)(scl   2) (nx 0) 0x00000000 __data_start__
[303](sec  1)(fl 0x00)(ty  20)(scl   2) (nx 0) 0x00002b08 _FreeLibrary@4
[304](sec  1)(fl 0x00)(ty   0)(scl   2) (nx 0) 0x00002b6c ___DTOR_LIST__
[305](sec  1)(fl 0x00)(ty  20)(scl   2) (nx 0) 0x00002a58 _free
[306](sec  6)(fl 0x00)(ty   0)(scl   2) (nx 0) 0x00000168 __imp__VirtualProtect@16
[307](sec  6)(fl 0x00)(ty   0)(scl   2) (nx 0) 0x000001ac __imp___onexit
[308](sec  1)(fl 0x00)(ty  20)(scl   2) (nx 0) 0x00002a98 ___p__fmode
[309](sec  6)(fl 0x00)(ty   0)(scl   2) (nx 0) 0x00000148 __imp__GetLastError@0
[310](sec  1)(fl 0x00)(ty  20)(scl   2) (nx 0) 0x00002ac8 _SetUnhandledExceptionFilter@4
[311](sec  6)(fl 0x00)(ty   0)(scl   2) (nx 0) 0x0000016c __imp__VirtualQuery@12
[312](sec  6)(fl 0x00)(ty   0)(scl   2) (nx 0) 0x0000013c __imp__FindNextFileA@8
[313](sec  8)(fl 0x00)(ty   0)(scl   2) (nx 0) 0x00000000 ___tls_start__
[314](sec  6)(fl 0x00)(ty   0)(scl   2) (nx 0) 0x00000164 __imp__TlsGetValue@4
[315](sec  6)(fl 0x00)(ty   0)(scl   2) (nx 0) 0x000005b0 __libmsvcrt_a_iname
[316](sec  6)(fl 0x00)(ty   0)(scl   2) (nx 0) 0x00000154 __imp__InitializeCriticalSection@4
[317](sec  1)(fl 0x00)(ty  20)(scl   2) (nx 0) 0x00002a88 __errno
[318](sec  1)(fl 0x00)(ty  20)(scl   2) (nx 0) 0x00002b38 _DeleteCriticalSection@4
[319](sec  3)(fl 0x00)(ty   0)(scl   2) (nx 0) 0x000002fc __rt_psrelocs_start
[320](sec  6)(fl 0x00)(ty   0)(scl   2) (nx 0) 0x000001b8 __imp__abort
[321](sec  7)(fl 0x00)(ty   0)(scl   2) (nx 0) 0x00000004 ___xl_c
[322](sec -1)(fl 0x00)(ty   0)(scl   2) (nx 0) 0x00000000 __dll_characteristics__
[323](sec -1)(fl 0x00)(ty   0)(scl   2) (nx 0) 0x00001000 __size_of_stack_commit__
[324](sec -1)(fl 0x00)(ty   0)(scl   2) (nx 0) 0x00200000 __size_of_stack_reserve__
[325](sec -1)(fl 0x00)(ty   0)(scl   2) (nx 0) 0x00000004 __major_subsystem_version__
[326](sec  7)(fl 0x00)(ty   0)(scl   2) (nx 0) 0x00000000 ___crt_xl_start__
[327](sec  7)(fl 0x00)(ty   0)(scl   2) (nx 0) 0x00000000 ___crt_xi_start__
[328](sec  7)(fl 0x00)(ty   0)(scl   2) (nx 0) 0x00000000 ___crt_xi_end__
[329](sec  6)(fl 0x00)(ty   0)(scl   2) (nx 0) 0x00000178 __imp__stricoll
[330](sec  7)(fl 0x00)(ty   0)(scl   2) (nx 0) 0x0000000c ___xl_z
[331](sec  6)(fl 0x00)(ty   0)(scl   2) (nx 0) 0x00000184 __imp____mb_cur_max
[332](sec  1)(fl 0x00)(ty  20)(scl   2) (nx 0) 0x00002af8 _GetLastError@0
[333](sec  1)(fl 0x00)(ty  20)(scl   2) (nx 0) 0x00002a30 _puts
[334](sec  6)(fl 0x00)(ty   0)(scl   2) (nx 0) 0x00000188 __imp____p__environ
[335](sec  6)(fl 0x00)(ty   0)(scl   2) (nx 0) 0x000001b0 __imp___pctype
[336](sec  1)(fl 0x00)(ty  20)(scl   2) (nx 0) 0x00002ab0 _VirtualQuery@12
[337](sec  5)(fl 0x00)(ty   0)(scl   2) (nx 0) 0x00000034 _mingw_initltsdrot_force
[338](sec  6)(fl 0x00)(ty   0)(scl   2) (nx 0) 0x000001a4 __imp___iob
[339](sec  1)(fl 0x00)(ty  20)(scl   2) (nx 0) 0x00002af0 _GetModuleHandleA@4
[340](sec  0)(fl 0x00)(ty  20)(scl   2) (nx 1) 0x00000000 ___register_frame_info
AUX tagndx 25 ttlsiz 0x1 lnnos 0 next 0
[342](sec  6)(fl 0x00)(ty   0)(scl   2) (nx 0) 0x00000528 __libmoldname_a_iname
[343](sec  5)(fl 0x00)(ty   0)(scl   2) (nx 0) 0x0000006c _hmod_libgcc
[344](sec -1)(fl 0x00)(ty   0)(scl   2) (nx 0) 0x00000000 .weak.___register_frame_info.___EH_FRAME_BEGIN__
[345](sec  6)(fl 0x00)(ty   0)(scl   2) (nx 0) 0x00000174 __imp__strdup
[346](sec  6)(fl 0x00)(ty   0)(scl   2) (nx 0) 0x000001a8 __imp___isctype
[347](sec  5)(fl 0x00)(ty   0)(scl   2) (nx 0) 0x00000000 __bss_start__
[348](sec  3)(fl 0x00)(ty   0)(scl   2) (nx 0) 0x000002fc ___RUNTIME_PSEUDO_RELOC_LIST_END__
[349](sec -1)(fl 0x00)(ty   0)(scl   2) (nx 0) 0x00000000 __fpreset
[350](sec -1)(fl 0x00)(ty   0)(scl   2) (nx 0) 0x00001000 __size_of_heap_commit__
[351](sec  6)(fl 0x00)(ty   0)(scl   2) (nx 0) 0x00000198 __imp___errno
[352](sec  1)(fl 0x00)(ty  20)(scl   2) (nx 0) 0x00002aa0 ___p__environ
[353](sec  6)(fl 0x00)(ty   0)(scl   2) (nx 0) 0x00000150 __imp__GetProcAddress@8
[354](sec  1)(fl 0x00)(ty  20)(scl   2) (nx 0) 0x00002ae8 _GetProcAddress@8
[355](sec  7)(fl 0x00)(ty   0)(scl   2) (nx 0) 0x00000010 ___crt_xp_start__
[356](sec  6)(fl 0x00)(ty   0)(scl   2) (nx 0) 0x000001f8 __imp__wcstombs
[357](sec  1)(fl 0x00)(ty  20)(scl   2) (nx 0) 0x00002a10 _strcoll
[358](sec  1)(fl 0x00)(ty  20)(scl   2) (nx 0) 0x00002b00 _GetCommandLineA@0
[359](sec  7)(fl 0x00)(ty   0)(scl   2) (nx 0) 0x00000010 ___crt_xp_end__
[360](sec  6)(fl 0x00)(ty   0)(scl   2) (nx 0) 0x000001e4 __imp__signal
[361](sec -1)(fl 0x00)(ty   0)(scl   2) (nx 0) 0x00000000 __dll__
[362](sec  6)(fl 0x00)(ty   0)(scl   2) (nx 0) 0x000001d8 __imp__puts
[363](sec -1)(fl 0x00)(ty   0)(scl   2) (nx 0) 0x00000000 __minor_os_version__
[364](sec  1)(fl 0x00)(ty  20)(scl   2) (nx 0) 0x00002a50 _fwrite
[365](sec  6)(fl 0x00)(ty   0)(scl   2) (nx 0) 0x000001bc __imp__atexit
[366](sec  6)(fl 0x00)(ty   0)(scl   2) (nx 0) 0x000001d0 __imp__mbstowcs
[367](sec  6)(fl 0x00)(ty   0)(scl   2) (nx 0) 0x00000028 __head_libmsvcrt_a
[368](sec -1)(fl 0x00)(ty   0)(scl   2) (nx 0) 0x00400000 __image_base__
[369](sec  1)(fl 0x00)(ty  20)(scl   2) (nx 0) 0x00002a78 __isctype
[370](sec -1)(fl 0x00)(ty   0)(scl   2) (nx 0) 0x00001000 __section_alignment__
[371](sec  1)(fl 0x00)(ty  20)(scl   2) (nx 0) 0x00002ad0 _LoadLibraryA@4
[372](sec  1)(fl 0x00)(ty  20)(scl   2) (nx 0) 0x000029f0 _wcstombs
[373](sec  6)(fl 0x00)(ty   0)(scl   2) (nx 0) 0x00000140 __imp__FreeLibrary@4
[374](sec  1)(fl 0x00)(ty  20)(scl   2) (nx 0) 0x00002a38 _memcpy
[375](sec  6)(fl 0x00)(ty   0)(scl   2) (nx 0) 0x00000200 __IAT_end__
[376](sec  6)(fl 0x00)(ty   0)(scl   2) (nx 0) 0x00000014 __head_libmoldname_a
[377](sec  3)(fl 0x00)(ty   0)(scl   2) (nx 0) 0x000002fc __RUNTIME_PSEUDO_RELOC_LIST__
[378](sec  1)(fl 0x00)(ty  20)(scl   2) (nx 0) 0x00002a20 _setlocale
[379](sec  6)(fl 0x00)(ty   0)(scl   2) (nx 0) 0x0000018c __imp____p__fmode
[380](sec  5)(fl 0x00)(ty   0)(scl   2) (nx 0) 0x00000004 __argc
[381](sec  8)(fl 0x00)(ty   0)(scl   2) (nx 0) 0x00000000 __tls_start
[382](sec  1)(fl 0x00)(ty  20)(scl   2) (nx 0) 0x00002b28 _ExitProcess@4
[383](sec  6)(fl 0x00)(ty   0)(scl   2) (nx 0) 0x000001e8 __imp__strcoll
[384](sec  2)(fl 0x00)(ty   0)(scl   2) (nx 0) 0x0000001c __data_end__
[385](sec  1)(fl 0x00)(ty  20)(scl   2) (nx 0) 0x00002aa8 ___getmainargs
[386](sec  1)(fl 0x00)(ty  20)(scl   2) (nx 0) 0x00002b20 _FindClose@4
[387](sec  1)(fl 0x00)(ty  20)(scl   2) (nx 0) 0x00002a00 _tolower
[388](sec  7)(fl 0x00)(ty   0)(scl   2) (nx 0) 0x00000000 ___xl_a
[389](sec  7)(fl 0x00)(ty   0)(scl   2) (nx 0) 0x00000008 ___xl_d
[390](sec  1)(fl 0x00)(ty   0)(scl   2) (nx 0) 0x00002b60 __CTOR_LIST__
[391](sec  1)(fl 0x00)(ty  20)(scl   2) (nx 0) 0x00002a40 _mbstowcs
[392](sec -1)(fl 0x00)(ty   0)(scl   2) (nx 0) 0x00000000 ___set_app_type
[393](sec  5)(fl 0x00)(ty   0)(scl   2) (nx 0) 0x00000064 __CRT_MT
[394](sec  5)(fl 0x00)(ty   0)(scl   2) (nx 0) 0x00000070 __bss_end__
[395](sec  5)(fl 0x00)(ty   0)(scl   2) (nx 0) 0x00000020 __CRT_fmode
[396](sec  7)(fl 0x00)(ty   0)(scl   2) (nx 0) 0x00000000 ___crt_xc_end__
[397](sec  5)(fl 0x00)(ty   0)(scl   2) (nx 0) 0x00000038 __tls_index
[398](sec  7)(fl 0x00)(ty   0)(scl   2) (nx 0) 0x00000000 ___crt_xc_start__
[399](sec  1)(fl 0x00)(ty  20)(scl   2) (nx 0) 0x00002b48 _strdup
[400](sec  5)(fl 0x00)(ty   0)(scl   2) (nx 0) 0x00000000 __argv
[401](sec  1)(fl 0x00)(ty   0)(scl   2) (nx 0) 0x00002b60 ___CTOR_LIST__
[402](sec  1)(fl 0x00)(ty  20)(scl   2) (nx 0) 0x00002a60 _calloc
[403](sec  2)(fl 0x00)(ty   0)(scl   2) (nx 0) 0x0000000c __fmode
[404](sec -1)(fl 0x00)(ty   0)(scl   2) (nx 0) 0x00000000 __rt_psrelocs_size
[405](sec  6)(fl 0x00)(ty   0)(scl   2) (nx 0) 0x000001d4 __imp__memcpy
[406](sec  1)(fl 0x00)(ty  20)(scl   2) (nx 0) 0x00002b10 _FindNextFileA@8
[407](sec -1)(fl 0x00)(ty   0)(scl   2) (nx 0) 0x00000200 __file_alignment__
[408](sec  6)(fl 0x00)(ty   0)(scl   2) (nx 0) 0x00000158 __imp__LeaveCriticalSection@4
[409](sec  1)(fl 0x00)(ty  20)(scl   2) (nx 0) 0x00002a28 _realloc
[410](sec  6)(fl 0x00)(ty   0)(scl   2) (nx 0) 0x000001cc __imp__malloc
[411](sec  4)(fl 0x00)(ty   0)(scl   2) (nx 0) 0x000000b8 ___EH_FRAME_BEGIN__
[412](sec -1)(fl 0x00)(ty   0)(scl   2) (nx 0) 0x00000004 __major_os_version__
[413](sec  6)(fl 0x00)(ty   0)(scl   2) (nx 0) 0x000001dc __imp__realloc
[414](sec  6)(fl 0x00)(ty   0)(scl   2) (nx 0) 0x00000128 __IAT_start__
[415](sec  1)(fl 0x00)(ty  20)(scl   2) (nx 0) 0x00002b40 _stricoll
[416](sec  8)(fl 0x00)(ty   0)(scl   2) (nx 0) 0x0000001c __tls_end
[417](sec  8)(fl 0x00)(ty   0)(scl   2) (nx 0) 0x00001000 __end__
[418](sec  6)(fl 0x00)(ty   0)(scl   2) (nx 0) 0x0000014c __imp__GetModuleHandleA@4
[419](sec  1)(fl 0x00)(ty  20)(scl   2) (nx 0) 0x00002a18 _signal
[420](sec  1)(fl 0x00)(ty  20)(scl   2) (nx 0) 0x00002a48 _malloc
[421](sec  1)(fl 0x00)(ty   0)(scl   2) (nx 0) 0x00002b6c __DTOR_LIST__
[422](sec  6)(fl 0x00)(ty   0)(scl   2) (nx 0) 0x0000019c __imp___fpreset
[423](sec -1)(fl 0x00)(ty   0)(scl   2) (nx 0) 0x00000000 .weak.___deregister_frame_info.___EH_FRAME_BEGIN__
[424](sec  1)(fl 0x00)(ty  20)(scl   2) (nx 0) 0x00002b30 _EnterCriticalSection@4
[425](sec  1)(fl 0x00)(ty  20)(scl   2) (nx 0) 0x00002a80 __fullpath
[426](sec -1)(fl 0x00)(ty   0)(scl   2) (nx 0) 0x00100000 __size_of_heap_reserve__
[427](sec  7)(fl 0x00)(ty   0)(scl   2) (nx 0) 0x00000010 ___crt_xt_start__
[428](sec -1)(fl 0x00)(ty   0)(scl   2) (nx 0) 0x00400000 ___ImageBase
[429](sec -1)(fl 0x00)(ty   0)(scl   2) (nx 0) 0x00000003 __subsystem__
[430](sec  6)(fl 0x00)(ty   0)(scl   2) (nx 0) 0x000001ec __imp__strlen
[431](sec -1)(fl 0x00)(ty   0)(scl   2) (nx 0) 0x00000000 .weak.__Jv_RegisterClasses.___EH_FRAME_BEGIN__
[432](sec  2)(fl 0x00)(ty   0)(scl   2) (nx 0) 0x00000008 __CRT_fenv
[433](sec  6)(fl 0x00)(ty   0)(scl   2) (nx 0) 0x000001c0 __imp__calloc
[434](sec  1)(fl 0x00)(ty  20)(scl   2) (nx 0) 0x00002a68 _abort
[435](sec  0)(fl 0x00)(ty  20)(scl   2) (nx 1) 0x00000000 __Jv_RegisterClasses
AUX tagndx 27 ttlsiz 0x1 lnnos 0 next 0
[437](sec  6)(fl 0x00)(ty   0)(scl   2) (nx 0) 0x00000180 __imp____getmainargs
[438](sec  8)(fl 0x00)(ty   0)(scl   2) (nx 0) 0x00000020 ___tls_end__
[439](sec  6)(fl 0x00)(ty   0)(scl   2) (nx 0) 0x00000130 __imp__ExitProcess@4
[440](sec  5)(fl 0x00)(ty   0)(scl   2) (nx 0) 0x0000002c _mingw_initltssuo_force
[441](sec  1)(fl 0x00)(ty  20)(scl   2) (nx 0) 0x00002ae0 _InitializeCriticalSection@4
[442](sec  5)(fl 0x00)(ty   0)(scl   2) (nx 0) 0x00000024 ___cpu_features
[443](sec  6)(fl 0x00)(ty   0)(scl   2) (nx 0) 0x000001c4 __imp__free
[444](sec  6)(fl 0x00)(ty   0)(scl   2) (nx 0) 0x00000160 __imp__SetUnhandledExceptionFilter@4
[445](sec  0)(fl 0x00)(ty  20)(scl   2) (nx 1) 0x00000000 ___deregister_frame_info
AUX tagndx 26 ttlsiz 0x1 lnnos 0 next 0
[447](sec -1)(fl 0x00)(ty   0)(scl   2) (nx 0) 0x00000001 __major_image_version__
[448](sec -1)(fl 0x00)(ty   0)(scl   2) (nx 0) 0x00000000 __loader_flags__
[449](sec  6)(fl 0x00)(ty   0)(scl   2) (nx 0) 0x000001f0 __imp__tolower
[450](sec  2)(fl 0x00)(ty   0)(scl   2) (nx 0) 0x00000004 __CRT_glob
[451](sec  1)(fl 0x00)(ty  20)(scl   2) (nx 0) 0x00002a70 __setmode
[452](sec  1)(fl 0x00)(ty   0)(scl   2) (nx 0) 0x00000fe0 ___chkstk_ms
[453](sec  6)(fl 0x00)(ty   0)(scl   2) (nx 0) 0x00000000 __head_libkernel32_a
[454](sec  3)(fl 0x00)(ty   0)(scl   2) (nx 0) 0x000002fc __rt_psrelocs_end
[455](sec  6)(fl 0x00)(ty   0)(scl   2) (nx 0) 0x00000194 __imp___cexit
[456](sec -1)(fl 0x00)(ty   0)(scl   2) (nx 0) 0x00000000 __minor_subsystem_version__
[457](sec  6)(fl 0x00)(ty   0)(scl   2) (nx 0) 0x00000134 __imp__FindClose@4
[458](sec -1)(fl 0x00)(ty   0)(scl   2) (nx 0) 0x00000000 __minor_image_version__
[459](sec  6)(fl 0x00)(ty   0)(scl   2) (nx 0) 0x000001f4 __imp__vfprintf
[460](sec  1)(fl 0x00)(ty  20)(scl   2) (nx 0) 0x00002a08 _strlen
[461](sec  6)(fl 0x00)(ty   0)(scl   2) (nx 0) 0x00000190 __imp____set_app_type
[462](sec  5)(fl 0x00)(ty   0)(scl   2) (nx 0) 0x00000030 _mingw_initltsdyn_force
[463](sec  1)(fl 0x00)(ty  20)(scl   2) (nx 0) 0x00002ac0 _TlsGetValue@4
[464](sec  6)(fl 0x00)(ty   0)(scl   2) (nx 0) 0x00000128 __imp__DeleteCriticalSection@4
[465](sec  1)(fl 0x00)(ty  20)(scl   2) (nx 0) 0x00002ad8 _LeaveCriticalSection@4
[466](sec  6)(fl 0x00)(ty   0)(scl   2) (nx 0) 0x00000144 __imp__GetCommandLineA@0
[467](sec  6)(fl 0x00)(ty   0)(scl   2) (nx 0) 0x0000015c __imp__LoadLibraryA@4
[468](sec  6)(fl 0x00)(ty   0)(scl   2) (nx 0) 0x000001e0 __imp__setlocale
[469](sec  3)(fl 0x00)(ty   0)(scl   2) (nx 0) 0x000002fc __RUNTIME_PSEUDO_RELOC_LIST_END__
[470](sec  6)(fl 0x00)(ty   0)(scl   2) (nx 0) 0x00000510 __libkernel32_a_iname
[471](sec  3)(fl 0x00)(ty   0)(scl   2) (nx 0) 0x0000007c ___dyn_tls_init_callback
[472](sec  8)(fl 0x00)(ty   0)(scl   2) (nx 0) 0x00000004 __tls_used
[473](sec  7)(fl 0x00)(ty   0)(scl   2) (nx 0) 0x00000010 ___crt_xt_end__
[474](sec  1)(fl 0x00)(ty  20)(scl   2) (nx 0) 0x000029f8 _vfprintf
[475](sec  6)(fl 0x00)(ty   0)(scl   2) (nx 0) 0x0000012c __imp__EnterCriticalSection@4
[476](sec  6)(fl 0x00)(ty   0)(scl   2) (nx 0) 0x000001c8 __imp__fwrite

Comments

Simon Marchi Dec. 20, 2018, 11:03 p.m. UTC | #1 
On 2018-12-20 10:45, Eli Zaretskii wrote:
>> Date: Wed, 19 Dec 2018 19:16:15 -0500
>> From: Simon Marchi <simon.marchi@polymtl.ca>
>> Cc: gdb-patches@sourceware.org
>> 
>> >   (top-gdb) p msymbol
>> >   $3 = {minsym = 0x10450d38, objfile = 0x10443b48}
>> >   (top-gdb) p msymbol.minsym.mginfo.name
>> >   $4 = 0x104485cd "__register_frame_info"
>> >   (top-gdb) p msymbol.minsym.mginfo
>> >   $5 = {name = 0x104485cd "__register_frame_info", value = {ivalue = 0,
>> >       block = 0x0, bytes = 0x0, address = 0x0, common_block = 0x0,
>> >       chain = 0x0}, language_specific = {obstack = 0x0, demangled_name
>> > = 0x0},
>> >     language = language_auto, ada_mangled = 0, section = 0}
>> 
>> Ok.  Well this is already strange.  Why is there an mst_text (code)
>> symbol with a value of 0?
> 
> Its address is zero because it's an unresolved symbol:
> 
>   d:\usr\eli>nm -A hello0.exe | fgrep " U "
>   hello0.exe:         U ___deregister_frame_info
>   hello0.exe:         U ___register_frame_info
>   hello0.exe:         U __Jv_RegisterClasses

Huh, interesting.  I looked at elfread, and similar undefined symbols 
are skipped:

https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;a=blob;f=gdb/elfread.c;h=71e6fcca6ec62ec57f93f06d8a9913612be6f9e2;hb=HEAD#l270

> This symbol comes from a weak symbol defined in MinGW crtbegin.o:
> 
>   d:\usr\eli>nm -A lib/gcc/mingw32/6.3.0/crtbegin.o | fgrep _frame_info
>   lib/gcc/mingw32/6.3.0/crtbegin.o:00000000 A
> .weak.___deregister_frame_info.___EH_FRAME_BEGIN__
>   lib/gcc/mingw32/6.3.0/crtbegin.o:00000000 A
> .weak.___register_frame_info.___EH_FRAME_BEGIN__
>   lib/gcc/mingw32/6.3.0/crtbegin.o:         w ___deregister_frame_info
>   lib/gcc/mingw32/6.3.0/crtbegin.o:         w ___register_frame_info

Is crtbegin.o an object file you link with statically when compiling 
with mingw?  If so, why would you end up with an undefined reference in 
the final executable?  Or is it linked dynamically at runtime?

>> If your binary is anything like those I can
>> produce with x86_64-w64-mingw32-gcc (and it looks similar, given the
>> addresses you show), your "image base" is likely 0x400000, and "base 
>> of
>> code" 0x1000 (0x401000 in absolute).  I found this information using
>> "objdump -x", in the header somewhere.  I therefore expect all text
>> symbols to be >= 0x401000.  I would start digging why this text symbol
>> with a value of 0 exists.
> 
> See above.  But please note that I use mingw.org's MinGW, and my
> executables are 32-bit, whereas you use MinGW64 and 64-bit
> executables.  So some details might be different; in particular, I
> don't think MinGW64 has this problematic symbol, because it's specific
> to the DWARF2 exception unwinding implemented in libgcc, which 64-bit
> Windows executables don't use.

Indeed, they are similar but not identical.  The file you provided as 
attachment is very useful to see what's in your binary.

>> It would be interesting to look at some other symbols in the msymbols
>> vector.  Are the other mst_text symbols >= 0x401000?
> 
> There are 2 more unresolved mst_text symbols, see above; they all have
> a zero address.  All the others are above 0x401000, indeed.
> 
> The lowest-address resolved minimal symbol whose type is mst_text is
> this:
> 
>   (top-gdb) p msymbol[22]
>   $112 = {mginfo = {name = 0x10447d95 "_mingw32_init_mainargs", value = 
> {
> 	ivalue = 4199072, block = 0x4012a0 <_mingw32_init_mainargs>,
> 	bytes = 0x4012a0 <_mingw32_init_mainargs> "Æ\222?<\215D$,\307D$\004",
> 	address = 0x4012a0, common_block = 0x4012a0 <_mingw32_init_mainargs>,
> 	chain = 0x4012a0 <_mingw32_init_mainargs>}, language_specific = {
> 	obstack = 0x0, demangled_name = 0x0}, language = language_auto,
>       ada_mangled = 0, section = 0}, size = 0, filename = 0x0, type = 
> mst_text,
>     created_by_gdb = 0, target_flag_1 = 0, target_flag_2 = 0, has_size 
> = 0,
>     hash_next = 0x0, demangled_hash_next = 0x0}
> 
> Interestingly, objdump shows this symbol in section 1:
> 
>   [  0](sec  1)(fl 0x00)(ty  20)(scl   2) (nx 0) 0x000002a0
> __mingw32_init_mainargs
> 
> whereas the above minsym information shows section = 0.  Is this
> expected?  If "real" symbols were to have section > 0, we could
> perhaps reject the unresolved ones.

Indeed.  I think the objdump output is misleading.  The indices in the 
"Sections:" section are 0-based.  But the indices in the "SYMBOL TABLE:" 
section look 1-based, as described here:

https://docs.microsoft.com/en-us/windows/desktop/debug/pe-format#coff-symbol-table
https://docs.microsoft.com/en-us/windows/desktop/debug/pe-format#section-number-values

So it looks like we should indeed skip symbols with section == 0.  We 
may also want to skip symbols with section == -1 (IMAGE_SYM_ABSOLUTE), 
such as __major_subsystem_version__.  I don't if anything relies on some 
of those symbols though.

>> Assuming this minimal symbol is wrong and assuming it wasn't there, 
>> then
>> I guess the search would fail and we would fall in the "Cannot find
>> bounds of current function" case of prepare_one_step?  That would be
>> appropriate in this case.
> 
> It's not wrong, but perhaps lookup_minimal_symbol_by_pc_section should
> reject unresolved symbols for this purpose.  However, the question is
> how?  One possibility is by their zero address.  (I don't see the weak
> attribute, or any other indication of its being unresolved, in the
> minimal symbol attributes.)
> 
> In any case, if we do call the "Cannot find bounds of current
> function" error, that will throw to the command loop, which I think is
> undesirable in this case.  We want GDB to step out of this code, not
> to error out.

When we have no line information for the current PC and the user asks us 
to step, we fall back to "single step until out of the current 
function".  But if the minimal symbol information doesn't let us know 
the bounds of the current function, then we can't "single step until out 
of the current function", because we don't know where it starts/end.

In your binary, the lowest .text function symbol is  
__mingw32_init_mainargs at 0x000002a0 (0x4012a0 once relocated).  Your 
pc is 0x40126d (according to an earlier message, but reading lower I 
realize this may not be valid anymore), which is lower.  So there's just 
no minimal symbol for GDB to find.  In that case, it sounds right to 
error our and say "I can't step, I don't have enough information".  The 
user can still use stepi.

Side-question, are there some debug symbols in the binary that could 
describe this location?  Which debug format (DWARF or equivalent) is 
generated when you use -g with mingw?

>> Ok, from what I understand, all these "mst_abs" symbols do not 
>> represent
>> addresses.  They just represent numerical "values", like version
>> numbers, alignment sizes, etc.  So it seems right to skip them when
>> looking for the minimal symbol preceding pc.
>> 
>> It looks like minimal_symbol_upper_bound is buggy, in that it should 
>> not
>> consider these mst_abs.  If we are looking for the end of a memory
>> range, we should not consider those symbols that do not even represent
>> memory addresses...
> 
> Indeed, the following change is enough to avoid the internal error:
> 
> --- gdb/minsyms.c~0	2018-07-04 18:41:59.000000000 +0300
> +++ gdb/minsyms.c	2018-12-20 08:06:11.516834500 +0200
> @@ -1514,7 +1514,8 @@ minimal_symbol_upper_bound (struct bound
>      {
>        if ((MSYMBOL_VALUE_RAW_ADDRESS (msymbol + i)
>  	   != MSYMBOL_VALUE_RAW_ADDRESS (msymbol))
> -	  && MSYMBOL_SECTION (msymbol + i) == section)
> +	  && MSYMBOL_SECTION (msymbol + i) == section
> +	  && MSYMBOL_TYPE (msymbol + i) != mst_abs)
>  	break;
>      }

Note that if we implement the solution of rejecting the symbols with 
section == -1, those mst_abs symbols won't be there anymore.

> However, it still shows the incorrect function name from the
> zero-address symbol:
> 
>   7       }
>   (gdb) n
>   0x00401288 in __register_frame_info ()
>   (gdb) n
>   Single stepping until exit from function __register_frame_info,
>   which has no line number information.
>   [Inferior 1 (process 10424) exited normally]
> 
> I think if we want to avoid showing __register_frame_info, we need
> further changes in lookup_minimal_symbol_by_pc_section.  But I don't
> see how this will help us, unless we also allow displaying the above
> message for functions whose names we don't know, perhaps saying
> something like
> 
>   Single stepping until exit from function <unknown>

The problem is not only that we are missing the name, but most 
importantly that we are missing the bounds of the current function.  
With what you've implemented here, GDB thinks there is a function that 
occupies the range [0,401000[ (something like that), so it single steps 
until it gets out of that range, but the process exits before.

So it kind of works for your use case, but it's not right, IMO.  If the 
process did not exit as it does here, the behavior would be erratic.  If 
GDB doesn't have the data to do something right, it should bail instead 
of doing something random.

>> 2. investigate if there should be some text symbol that should really
>> contain 0x0040126d, that for some reason does not end up in GDB's
>> minimal symbol table.
> 
> The function in which the PC value of 0x401288 lives is
> __mingw_CRTStartup, which ends like this:
> 
>   /* Call the main() function. If the user does not supply one
>    * the one in the 'libmingw32.a' library will be linked in, and
>    * that one calls WinMain().  See main.c in the 'lib' directory
>    * for more details.
>    */
>   nRet = main (_argc, _argv, environ);
> 
>   /* Perform exit processing for the C library. This means flushing
>    * output and calling atexit() registered functions.
>    */
>   _cexit ();
> 
>   ExitProcess (nRet);
> }
> 
> This function is declared in the MinGW runtime sources as follows:
> 
>   static __MINGW_ATTRIB_NORETURN void __mingw_CRTStartup (void);
> 
> But its symbol is not in the symbol table.  Not sure why, perhaps
> because it's a static function?  But the code is there, starting at
> the address 0x4011b0.  The last part, after exiting 'main', which
> corresponds to the above source snippet is this:
> 
>   (gdb) disassemble 0x401283,0x401294
>   Dump of assembler code from 0x401283 to 0x401294:
>      0x00401283 <__register_frame_info+4199043>:  call   0x401460 
> <main>
>      0x00401288 <__register_frame_info+4199048>:  mov    %eax,%ebx
>      0x0040128a <__register_frame_info+4199050>:  call   0x403a90 
> <_cexit>
>      0x0040128f <__register_frame_info+4199055>:  mov    %ebx,(%esp)
>      0x00401292 <__register_frame_info+4199058>:  call   0x403b28
> <ExitProcess@4>
> 
> So when this problem happens, we are at the "mov %eax,%ebx"
> instruction after exiting 'main', as I'd expect.

Ok, well I think it shows the problem quite clearly, some symbol is 
missing for GDB to work properly in that context.  I think that we 
should improve GDB to handle it better error out clearly (instead of 
hitting a failed assert), but I don't think it can do much more.

I guess that having debug info for the file containing 
__mingw_CRTStartup would help, if you really needed to step past main?

Simon
Eli Zaretskii Dec. 22, 2018, 8:44 a.m. UTC | #2 
> Date: Thu, 20 Dec 2018 18:03:33 -0500
> From: Simon Marchi <simon.marchi@polymtl.ca>
> Cc: gdb-patches@sourceware.org
> 
> >> Ok.  Well this is already strange.  Why is there an mst_text (code)
> >> symbol with a value of 0?
> > 
> > Its address is zero because it's an unresolved symbol:
> > 
> >   d:\usr\eli>nm -A hello0.exe | fgrep " U "
> >   hello0.exe:         U ___deregister_frame_info
> >   hello0.exe:         U ___register_frame_info
> >   hello0.exe:         U __Jv_RegisterClasses
> 
> Huh, interesting.  I looked at elfread, and similar undefined symbols 
> are skipped:
> 
> https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;a=blob;f=gdb/elfread.c;h=71e6fcca6ec62ec57f93f06d8a9913612be6f9e2;hb=HEAD#l270

So maybe GDB should skip them as well?

> > This symbol comes from a weak symbol defined in MinGW crtbegin.o:
> > 
> >   d:\usr\eli>nm -A lib/gcc/mingw32/6.3.0/crtbegin.o | fgrep _frame_info
> >   lib/gcc/mingw32/6.3.0/crtbegin.o:00000000 A
> > .weak.___deregister_frame_info.___EH_FRAME_BEGIN__
> >   lib/gcc/mingw32/6.3.0/crtbegin.o:00000000 A
> > .weak.___register_frame_info.___EH_FRAME_BEGIN__
> >   lib/gcc/mingw32/6.3.0/crtbegin.o:         w ___deregister_frame_info
> >   lib/gcc/mingw32/6.3.0/crtbegin.o:         w ___register_frame_info
> 
> Is crtbegin.o an object file you link with statically when compiling 
> with mingw?

Yes.  This file comes with MinGW GCC.

> If so, why would you end up with an undefined reference in 
> the final executable?  Or is it linked dynamically at runtime?

AFAIU, these symbols are only resolved when linking a Java program
using gcj.  See the comments in GCC's source file
libgcc/config/i386/cygming-crtbegin.c, which is where crtbegin.o comes
from.

> > In any case, if we do call the "Cannot find bounds of current
> > function" error, that will throw to the command loop, which I think is
> > undesirable in this case.  We want GDB to step out of this code, not
> > to error out.
> 
> When we have no line information for the current PC and the user asks us 
> to step, we fall back to "single step until out of the current 
> function".  But if the minimal symbol information doesn't let us know 
> the bounds of the current function, then we can't "single step until out 
> of the current function", because we don't know where it starts/end.
> 
> In your binary, the lowest .text function symbol is  
> __mingw32_init_mainargs at 0x000002a0 (0x4012a0 once relocated).  Your 
> pc is 0x40126d (according to an earlier message, but reading lower I 
> realize this may not be valid anymore), which is lower.  So there's just 
> no minimal symbol for GDB to find.  In that case, it sounds right to 
> error our and say "I can't step, I don't have enough information".  The 
> user can still use stepi.

But this use case is somewhat special, IMO: stepping outside of 'main'
can happen unintentionally, and should not cause an error.  It should
let the inferior run to completion without any errors.  Raising an
error in this case is confusing.

> Side-question, are there some debug symbols in the binary that could 
> describe this location?

How do I know that?

> Which debug format (DWARF or equivalent) is generated when you use
> -g with mingw?

It's DWARF2 version 4.

> > --- gdb/minsyms.c~0	2018-07-04 18:41:59.000000000 +0300
> > +++ gdb/minsyms.c	2018-12-20 08:06:11.516834500 +0200
> > @@ -1514,7 +1514,8 @@ minimal_symbol_upper_bound (struct bound
> >      {
> >        if ((MSYMBOL_VALUE_RAW_ADDRESS (msymbol + i)
> >  	   != MSYMBOL_VALUE_RAW_ADDRESS (msymbol))
> > -	  && MSYMBOL_SECTION (msymbol + i) == section)
> > +	  && MSYMBOL_SECTION (msymbol + i) == section
> > +	  && MSYMBOL_TYPE (msymbol + i) != mst_abs)
> >  	break;
> >      }
> 
> Note that if we implement the solution of rejecting the symbols with 
> section == -1, those mst_abs symbols won't be there anymore.

Fine by me.  Should we push such a change?

> > I think if we want to avoid showing __register_frame_info, we need
> > further changes in lookup_minimal_symbol_by_pc_section.  But I don't
> > see how this will help us, unless we also allow displaying the above
> > message for functions whose names we don't know, perhaps saying
> > something like
> > 
> >   Single stepping until exit from function <unknown>
> 
> The problem is not only that we are missing the name, but most 
> importantly that we are missing the bounds of the current function.  
> With what you've implemented here, GDB thinks there is a function that 
> occupies the range [0,401000[ (something like that), so it single steps 
> until it gets out of that range, but the process exits before.

Which IMO is just fine for this specific use case.

> So it kind of works for your use case, but it's not right, IMO.  If the 
> process did not exit as it does here, the behavior would be erratic.

I don't think it would be erratic, we will just see the same

    0x00401nnn in __register_frame_info ()  

for several steps.  Is that so bad?

> Ok, well I think it shows the problem quite clearly, some symbol is 
> missing for GDB to work properly in that context.  I think that we 
> should improve GDB to handle it better error out clearly (instead of 
> hitting a failed assert), but I don't think it can do much more.

Can you suggest a patch?  I'm not sure I understand the behavior that
will be the result.

> I guess that having debug info for the file containing 
> __mingw_CRTStartup would help, if you really needed to step past main?

I don't need to step past main, it just happens in many cases, when I
type one "next" too many.  I would like to avoid any errors in that
case.
Simon Marchi Dec. 22, 2018, 4:47 p.m. UTC | #3 
On 2018-12-22 03:44, Eli Zaretskii wrote:
>> Date: Thu, 20 Dec 2018 18:03:33 -0500
>> From: Simon Marchi <simon.marchi@polymtl.ca>
>> Cc: gdb-patches@sourceware.org
>> 
>> >> Ok.  Well this is already strange.  Why is there an mst_text (code)
>> >> symbol with a value of 0?
>> >
>> > Its address is zero because it's an unresolved symbol:
>> >
>> >   d:\usr\eli>nm -A hello0.exe | fgrep " U "
>> >   hello0.exe:         U ___deregister_frame_info
>> >   hello0.exe:         U ___register_frame_info
>> >   hello0.exe:         U __Jv_RegisterClasses
>> 
>> Huh, interesting.  I looked at elfread, and similar undefined symbols
>> are skipped:
>> 
>> https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;a=blob;f=gdb/elfread.c;h=71e6fcca6ec62ec57f93f06d8a9913612be6f9e2;hb=HEAD#l270
> 
> So maybe GDB should skip them as well?

Yes.  Can you please give it a try it?

>> > In any case, if we do call the "Cannot find bounds of current
>> > function" error, that will throw to the command loop, which I think is
>> > undesirable in this case.  We want GDB to step out of this code, not
>> > to error out.
>> 
>> When we have no line information for the current PC and the user asks 
>> us
>> to step, we fall back to "single step until out of the current
>> function".  But if the minimal symbol information doesn't let us know
>> the bounds of the current function, then we can't "single step until 
>> out
>> of the current function", because we don't know where it starts/end.
>> 
>> In your binary, the lowest .text function symbol is
>> __mingw32_init_mainargs at 0x000002a0 (0x4012a0 once relocated).  Your
>> pc is 0x40126d (according to an earlier message, but reading lower I
>> realize this may not be valid anymore), which is lower.  So there's 
>> just
>> no minimal symbol for GDB to find.  In that case, it sounds right to
>> error our and say "I can't step, I don't have enough information".  
>> The
>> user can still use stepi.
> 
> But this use case is somewhat special, IMO: stepping outside of 'main'
> can happen unintentionally, and should not cause an error.  It should
> let the inferior run to completion without any errors.  Raising an
> error in this case is confusing.

Just a precision, it's not the stepping out of main that causes an 
error, it's trying to step again:

<in main>
(gdb) step
<out of main>
(gdb) step
Cannot find bounds of current function

Perhaps the error message could be improved, but I think this is the 
right thing to do.  It is often reported as a bug when "step" lets the 
program run free and acts as "continue".  If you find yourself in that 
situation again, why not just use "continue" to let the program exit?

This case would work just fine if your binary had a matching symbol for 
this location, so I would start looking at the toolchain, see if can 
provide that.

>> Side-question, are there some debug symbols in the binary that could
>> describe this location?
> 
> How do I know that?

I would normally use "readelf --debug-dump" to look at the DWARF info, 
but since this is not an ELF, I don't know.

>> > --- gdb/minsyms.c~0	2018-07-04 18:41:59.000000000 +0300
>> > +++ gdb/minsyms.c	2018-12-20 08:06:11.516834500 +0200
>> > @@ -1514,7 +1514,8 @@ minimal_symbol_upper_bound (struct bound
>> >      {
>> >        if ((MSYMBOL_VALUE_RAW_ADDRESS (msymbol + i)
>> >  	   != MSYMBOL_VALUE_RAW_ADDRESS (msymbol))
>> > -	  && MSYMBOL_SECTION (msymbol + i) == section)
>> > +	  && MSYMBOL_SECTION (msymbol + i) == section
>> > +	  && MSYMBOL_TYPE (msymbol + i) != mst_abs)
>> >  	break;
>> >      }
>> 
>> Note that if we implement the solution of rejecting the symbols with
>> section == -1, those mst_abs symbols won't be there anymore.
> 
> Fine by me.  Should we push such a change?

Based on what we saw, I would be for it.  But you'll need to make the 
change and test it for regression, as I don't have the necessary setup 
(and knowledge) to do that on Windows.

>> > I think if we want to avoid showing __register_frame_info, we need
>> > further changes in lookup_minimal_symbol_by_pc_section.  But I don't
>> > see how this will help us, unless we also allow displaying the above
>> > message for functions whose names we don't know, perhaps saying
>> > something like
>> >
>> >   Single stepping until exit from function <unknown>
>> 
>> The problem is not only that we are missing the name, but most
>> importantly that we are missing the bounds of the current function.
>> With what you've implemented here, GDB thinks there is a function that
>> occupies the range [0,401000[ (something like that), so it single 
>> steps
>> until it gets out of that range, but the process exits before.
> 
> Which IMO is just fine for this specific use case.

Yes, but it's by chance.  If the process didn't exit, it wouldn't be 
"Single stepping until exit from function X", it would be "Single 
stepping until god-knows-when". So it might work fine here, but if we 
adopted this behavior generally, it could just be more confusing in 
other cases.

>> So it kind of works for your use case, but it's not right, IMO.  If 
>> the
>> process did not exit as it does here, the behavior would be erratic.
> 
> I don't think it would be erratic, we will just see the same
> 
>     0x00401nnn in __register_frame_info ()
> 
> for several steps.  Is that so bad?

Well, first thing, I think it's wrong that we show that it's in 
__register_frame_info.  If this was an actual resolved .text symbol, it 
wouldn't be so bad, but here it's not even a function in the program, it 
doesn't make sense.

Also, the user wouldn't do several step.  They would do one step and GDB 
would keep single stepping until execution gets out of the stepping 
range [0,401000[.  This is very unpredictable, from the point of view of 
the user.

>> Ok, well I think it shows the problem quite clearly, some symbol is
>> missing for GDB to work properly in that context.  I think that we
>> should improve GDB to handle it better error out clearly (instead of
>> hitting a failed assert), but I don't think it can do much more.
> 
> Can you suggest a patch?  I'm not sure I understand the behavior that
> will be the result.

I could try later, using a mingw64 executable (though I can't run it, 
just read the symbols in GDB).  But I think you are in a better position 
than me to do that, since you are more familiar with the platform.

I would probably be looking into adding some "if" in coff_symtab_read, 
to filter out the unwanted symbols, as discussed previously.  You can 
now use "set debug symtab -create 2" to confirm that symbols like 
__register_frame_info no longer lead to the creation of a minimal 
symbol.

>> I guess that having debug info for the file containing
>> __mingw_CRTStartup would help, if you really needed to step past main?
> 
> I don't need to step past main, it just happens in many cases, when I
> type one "next" too many.  I would like to avoid any errors in that
> case.

As I mentioned earlier, I think it's fine if step fails with "I don't 
have enough info to do my work", and suggest you use continue instead.

Simon
Joel Brobecker Dec. 23, 2018, 5:35 a.m. UTC | #4 
> > > Side-question, are there some debug symbols in the binary that could
> > > describe this location?
> > 
> > How do I know that?
> 
> I would normally use "readelf --debug-dump" to look at the DWARF info, but
> since this is not an ELF, I don't know.

Objdump has the same kind of functionality for both DWARF and
the symbol table (--dwarf, -t, -T, etc).
Eli Zaretskii Dec. 23, 2018, 3:23 p.m. UTC | #5 
> Date: Sun, 23 Dec 2018 09:35:02 +0400
> From: Joel Brobecker <brobecker@adacore.com>
> Cc: Eli Zaretskii <eliz@gnu.org>, gdb-patches@sourceware.org
> 
> > > > Side-question, are there some debug symbols in the binary that could
> > > > describe this location?
> > > 
> > > How do I know that?
> > 
> > I would normally use "readelf --debug-dump" to look at the DWARF info, but
> > since this is not an ELF, I don't know.
> 
> Objdump has the same kind of functionality for both DWARF and
> the symbol table (--dwarf, -t, -T, etc).

Yes.  But in what part of its output would you expect to see debug
symbols that describe this location?
Simon Marchi Dec. 23, 2018, 3:32 p.m. UTC | #6 
On 2018-12-23 10:23 a.m., Eli Zaretskii wrote:
>> Date: Sun, 23 Dec 2018 09:35:02 +0400
>> From: Joel Brobecker <brobecker@adacore.com>
>> Cc: Eli Zaretskii <eliz@gnu.org>, gdb-patches@sourceware.org
>>
>>>>> Side-question, are there some debug symbols in the binary that could
>>>>> describe this location?
>>>>
>>>> How do I know that?
>>>
>>> I would normally use "readelf --debug-dump" to look at the DWARF info, but
>>> since this is not an ELF, I don't know.
>>
>> Objdump has the same kind of functionality for both DWARF and
>> the symbol table (--dwarf, -t, -T, etc).
> 
> Yes.  But in what part of its output would you expect to see debug
> symbols that describe this location?
> 

If you use "objdump --dwarf=info <binary>", then you can see some nodes representing
subprograms (functions), like this:

 <1><51>: Abbrev Number: 5 (DW_TAG_subprogram)
    <52>   DW_AT_external    : 1
    <52>   DW_AT_name        : (indirect string, offset: 0x257b): main
    <56>   DW_AT_decl_file   : 1
    <57>   DW_AT_decl_line   : 6
    <58>   DW_AT_decl_column : 5
    <59>   DW_AT_type        : <0x4a>
    <5d>   DW_AT_low_pc      : 0x1119
    <65>   DW_AT_high_pc     : 0xb
    <6d>   DW_AT_frame_base  : 1 byte block: 9c 	(DW_OP_call_frame_cfa)
    <6f>   DW_AT_GNU_all_call_sites: 1


Here, DW_AT_high_pc is actually an offset relative to DW_AT_low_pc. This means
my function main's range is [0x1119,0x1119+0xb[.  So you could search in that
output for "__mingw_CRTStartup", to see if there's a node describing that function.

Honestly, I would be quite surprised if you had DWARF info for it but not a basic
COFF symbol, but it costs nothing to check.

Simon
diff mbox

Patch

--- gdb/minsyms.c~0	2018-07-04 18:41:59.000000000 +0300
+++ gdb/minsyms.c	2018-12-20 08:06:11.516834500 +0200
@@ -1514,7 +1514,8 @@  minimal_symbol_upper_bound (struct bound
     {
       if ((MSYMBOL_VALUE_RAW_ADDRESS (msymbol + i)
 	   != MSYMBOL_VALUE_RAW_ADDRESS (msymbol))
-	  && MSYMBOL_SECTION (msymbol + i) == section)
+	  && MSYMBOL_SECTION (msymbol + i) == section
+	  && MSYMBOL_TYPE (msymbol + i) != mst_abs)
 	break;
     }