Path: utzoo!attcan!uunet!husc6!uwvax!oddjob!tank!uxc!uxc.cso.uiuc.edu!a.cs.uiuc.edu!m.cs.uiuc.edu!wsmith
From: wsmith@m.cs.uiuc.edu
Newsgroups: comp.lang.c
Subject: Re: Portable uses of jmpbuf's
Message-ID: <4700023@m.cs.uiuc.edu>
Date: 11 Oct 88 20:12:00 GMT
References: <4700022@m.cs.uiuc.edu>
Lines: 31
Nf-ID: #R:m.cs.uiuc.edu:4700022:m.cs.uiuc.edu:4700023:000:1313
Nf-From: m.cs.uiuc.edu!wsmith    Oct 11 15:12:00 1988


>/* ---------- "Portable uses of jmpbuf's" ---------- */
>How do you portably pass a jmpbuf as a parameter to a C function?
>
>Some machines define a jmpbuf to be struct { stuff } , while
>others define a jmpbuf to be an array.  In one case, an & is required, 
>while in the other case it is not.
>
>My best solution was to define my own structure with one field of a 
>jmpbuf and then always take the address.
>
>Is there a better way?

Here is a more detailed description of the problem:

If I have a function that I want to pass the address of a jmpbuf to it,
with "typedef struct {} jmpbuf;", the call to the function will be
"function(&a_jmpbuf);" and the prototype ala Microsoft C will be 
"function( jmpbuf * a );"

With "typedef int jmpbuf[10];", the call to the function will be
"function(a_jmpbuf);" and the prototype will be "function( jmpbuf a );"
because the array gets converted into a pointer to its first element when
I make the call.  If I try to make the prototype "function( jmpbuf * a) ;",
the call will no longer match even if make the call be the same as with
the struct version of jmpbuf.

I have heard that one fix is to wait for an ANSI compatible compiler which
will allow "function(&a_jmpbuf);" and "function(jmpbuf * a);" in either case.

Bill Smith	uiucdcs!wsmith		wsmith@cs.uiuc.edu