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From: Chris Faylor <cgf AT cygnus DOT com>
Date: Thu, 22 Apr 1999 23:51:53 -0400
To: cygwin AT sourceware DOT cygnus DOT com
Subject: Re: STDIN redirection under GDB
Message-ID: <19990422235153.B19629@cygnus.com>
References: <371DE8D2 DOT 7AE94AA2 AT ilc DOT pi DOT cnr DOT it> <Pine DOT SUN DOT 3 DOT 93 DOT 990421124838 DOT 11231A-100000 AT modi DOT xraylith DOT wisc DOT edu>
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In-Reply-To: <Pine.SUN.3.93.990421124838.11231A-100000@modi.xraylith.wisc.edu>; from Mumit Khan on Wed, Apr 21, 1999 at 01:20:03PM -0500

On Wed, Apr 21, 1999 at 01:20:03PM -0500, Mumit Khan wrote:
>On Wed, 21 Apr 1999, Stefano Federici wrote:
>> I found a similar question in a letter to the list on 1995, but I did
>> not find any answer.
>> I'm having problems using GDB with a program that uses standard-input.
>> I uses gdb 4.17.1 delivered with cygwinb20.1 (I also installed
>> egcs.1.1.2, but I don't know if it can influence in any way this
>> behaviour).
>> All is well when running (other) programs that do not use stdin.  I use
>> this form of the run command:
>> 
>>     run < input
>> 
>> Where 'input' is my input file, in the current directory.  GDB just sits
>> 
>> there, forever. I can only break the loop by typing CTRL-C and obtain
>> the debugger prompt.
>> I also tried to use the argument setting options:
>> 
>>    set args < input
>> 
>> but the result is exactly the same.
>> 
>> Has anyone seen this type of behavior?
>> Can it depend on the binary/text mode of cygwin?
>> 
>
>It's a bug in all Win32 ports of gdb.
>
>This has to do with how GDB starts a "inferior" subprocess that it
>wants to debug; on Unix, it uses the shell to do the redirection, but
>on win32, gdb uses CreateProcess. Currently, the cmd arg parser in
>win32/gdb doesn't look for redirection symbols, and so it doesn't do
>what you'd expect.  Also, someone has to write the small piece of code
>that does the redirection by passing the descriptor to CreateProcess
>etc.
>
>See target.c (child_create_inferior) for how it's done on Unix boxes and
>win32-nat.c (child_create_inferior) for how it's done on win32. 
>
>It can be fixed without too much trouble, but someone needs to do it.

Actually, I've looked into fixing it in the past and it's more trouble
than it appears.

cgf

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