Subject: SIGINT handler not called during blocking pipe read
From: "greg" <[email-masked]>
To: <[email-masked]>
Cc: <"[email-masked]"@delorie.com>
Date: Fri, 12 Oct 2007 10:26:25 -0400
List-Id: <cygwin.cygwin.com>

I'm trying to use a Cygwin-linked program as a subprocess in Eclipse.
As spawned in this environment, if a SIGINT is sent to the process when
it is blocked reading from stdin (connected to a pipe in this case), the
SIGINT handler is not being called.

In an attempt to reduce the scenario to its essentials, I was able to
replicate the symptoms with a minimal outside-of-Eclipse scenario below.

Is this expected behavior with respect to SIGINT during a pipe read?

--

/*  
 *  File name: catchsigint.c
 *
 *  A pared-down example illustrating SIGINT handler not being
 *  called when SIGINT received while process is blocked waiting
 *  for a read from pipe.
 *  
 *  The symptoms are seen with Cygwin 1.5.24-2 as well as earler
 *  versions, on Windows XP+SP2 and Win2K.
 *  
 *  To build:  gcc -o catchsigint.exe catchsigint.c
 *  
 *  Steps to reproduce symptoms:
 *  
 *  1) From the Windows Start menu, open a native Windows command
 *  prompt.
 *
 *  2) Launch this example program (catchsigint.exe) from the native 
 *  Windows command prompt, with stdin coming from a pipe.
 *  
 *  C:\temp>cat | catchsigint
 *  
 *  3) As the catchsigint process is blocked waiting for input from
 *  the pipe, send SIGINT to the catchsigint process via 
 *  "kill -SIGINT pid" from a Cygwin shell.
 *
 */

#include <stdio.h>
#include <signal.h>

void handler(int sig) {
   printf("SIGINT caught\n");
   exit(-1);
}

int main() {
   signal(SIGINT, handler);
   /*  The following sets up a blocking read,
       then we'll send a SIGINT from outside */
   getchar();  
   return 0;
}

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