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Date: Mon, 01 Feb 1999 01:03:39 -0500
To: djgpp AT delorie DOT com
From: Paul Derbyshire <pderbysh AT usa DOT net>
Subject: Questions re: signals
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Reply-To: djgpp AT delorie DOT com

I have several questions regarding signals. A search of the faq, info
files, website, and archive only partially answered these.


1. DJGPP 2.02 masks FPU exceptions by default but earlier DJGPPs do 
   not.
   -- Is there a #define that will distinguish DJGPP 2.02 and later 
      versions from earlier versions? Not critically important.
   -- In pre-2.02, FPU exceptions are masked using _control87.
      The info files show _control87 accepting two unsigned ints, one
      called a 'new control word' the other a 'mask'. It isn't
      made clear, however, how the _control87 combines these with the
      FPU state. Like, does it OR with the 'new control word' and
      AND with the 'mask' or what, precisely? The mailing list 
      archives did not answer this. This IS important!
   -- Do other Intel arch GCC development environments (Cygnus, 
      etc.) behave consistently about the FPU? Do all support
      a _control87 in float.h with the exact same syntax and 
      semantics?
   -- Non-GCC DOS and Windows compilers -- How do these manage
      FPU exceptions?
   -- How are FPU exceptions managed under Linux using GCC, or 
      using other compilers?
   -- How do other CPU architectures manage FPU exceptions?
2. The signal handling mechanism for setting signal handlers and
   the like is uniform among POSIX-compliant development 
   environments right?
3. Is there a standard C/C++ library function to launch an external 
   app synchronously regardless of whether the OS has multitasking 
   support?
4. Is there a way to launch a child program and capture stderr
   from it, but not stdout? (I assume yes since the DJ util redir
   must do it.) Is there such a method that is uniform across
   many operating systems?
5. What happens to a DJGPP app if it launches a child that catches
   a fatal signal, e.g. SIGSEGV? Is there a way to ensure that
   the launching app stays stable and perceives it as the child
   returning errorlevel 255? How does this translate to Linux
   and other protected mode environments?
-- 
   .*.  "Clouds are not spheres, mountains are not cones, coastlines are not
-()  <  circles, and bark is not smooth, nor does lightning travel in a
   `*'  straight line."    -------------------------------------------------
        -- B. Mandelbrot  |http://surf.to/pgd.net
_____________________ ____|________     Paul Derbyshire     pderbysh AT usa DOT net
Programmer & Humanist|ICQ: 10423848|