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Subject:	RE: MS or cygwin dll debug tools/ was "sys/sockio.h" etc.
Date:	Wed, 28 May 2008 15:38:27 -0400
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> first instruction of the binary. There is no such "can't debug before
> main" restriction.
>

I think what bothered me is I just tried to step it to get minimum initial 
increment and that bombed- so I just assumed it wouldn't be early enough.
In any case, it looked like I needed to instrument the loading process, 

(gdb) info functions CRT
All functions matching regular expression "CRT":

Non-debugging symbols:
0x00401000  WinMainCRTStartup
0x00401000  mainCRTStartup
(gdb) info target
Symbols from "/cygdrive/e/new/temp/nmap/src3/nmap-4.62/a.exe".
Local exec file:
        `/cygdrive/e/new/temp/nmap/src3/nmap-4.62/a.exe', file type pei-i386.
        Entry point: 0x401000
        0x00401000 - 0x004e9608 is .text
        0x004ea000 - 0x004ebaa0 is .data
        0x004ec000 - 0x00509c24 is .rdata
        0x0050a000 - 0x00519b50 is .bss
        0x0051a000 - 0x0051bfa8 is .idata
(gdb) b *0x0401000
Breakpoint 1 at 0x401000
(gdb) run
Starting program: /cygdrive/e/new/temp/nmap/src3/nmap-4.62/a.exe

Program received signal SIGSEGV, Segmentation fault.

Program received signal SIGSEGV, Segmentation fault.

Program received signal SIGSEGV, Segmentation fault.

Program exited with code 0200.
You can't do that without a process to debug.
(gdb)

> Date: Wed, 28 May 2008 08:36:33 -0700
> From: brian AT dessent DOT net
> To: gchicares AT sbcglobal DOT net
> CC: cygwin AT cygwin DOT com
> Subject: Re: MS or cygwin dll debug tools/ was "sys/sockio.h" etc.
>
> Greg Chicares wrote:
>
>> Using cygwin's gdb on a MinGW app, I can set this breakpoint
>> b '__mingw_CRTStartup'
>> on the function that invokes main(), and then examine variables
>> before main() is invoked. For a Cygwin app, I guess you'd break
>> on 'mainCRTStartup'. Does that breakpoint happen early enough to
>> meet your needs?
>
> You can also do "info target" to display the entry point and then set a
> breakpoint on it as e.g. "b *0x401000" if you want to start at the very
> first instruction of the binary. There is no such "can't debug before
> main" restriction.
>
> Brian
>
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