From: Ben Decker <bdeck AT lycos DOT co DOT uk>
To: djgpp-workers AT delorie DOT com
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Subject: RE: Re: your mail
Date: Wed, 15 Jan 2003 22:31:38 +0100
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Hello.

> ------- Original Message ------- 
> From : sandmann AT clio DOT rice DOT edu (Charles Sandmann)
> Date : Sun, 5 Jan 2003 21:15:08 -0600 (CST)
>> > > But (at least this version) needs a second stack (probably for keeping track
>> > > of mutex, i don't know...). DJGPP has no sigstack or sigaltstack.
>Take a look at go32/dpmiexcp.c and go32/exceptn.S
>
>The documentation I have for sigstack looks like it would be fairly 
>straightforward to implement - the current exception stack is declared
>in exceptn.S 

According to the man pages:
"sigstack() is to be obsoleted at a future date.

"A portable application, when being written or rewritten, should use sigaltstack() instead 
of sigstack()."


The sigaltstack structure is defined as:
struct sigaltstack {
             char   *ss_sp;
             int     ss_size;
             int     ss_flags;
     };
(would this go in signal.h? ss_size may better be difined as size_t?)
It is a bit confusing, because the structure is similar to stack_t (I notice DJGPP doesn't 
have that either). The values seem normally defined as follows:
ss_sp = malloc(SIGSTKSZ)
ss_size = SIGSTKSZ;
ss_flags = 0;
SIGSTKSZ is "the number of bytes/chars that would be used to cover the usual case 
when allocating an alternate stack area."

For Linux it was defined as:
#define MINSIGSTKSZ     131027  /* min. stack size for sigaltstack() */
#define SIGSTKSZ        262144  /* default stack size for sigaltstack() */


GNU platforms seem to store the sigaltstack() routine itself in a separate 'sigaltstack.c'. 
Would this also be suitable for DJGPP?

Ben

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