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From: notes@hcx1.UUCP
Newsgroups: comp.lang.c
Subject: structure function returns -- how?
Message-ID: <131@hcx1.UUCP>
Date: Fri, 5-Dec-86 08:55:26 EST
Article-I.D.: hcx1.131
Posted: Fri Dec  5 08:55:26 1986
Date-Received: Sun, 7-Dec-86 03:34:47 EST
Sender: notes@hcx1.UUCP
Organization: Harris CSD, Fort Lauderdale, Florida
Lines: 21
Nf-ID: #N:hcx1:44100002:000:896
Nf-From: hcx1!daver    Dec  5 07:08:00 1986

Suppose   a   is declared as a structure and   b   is a function which 
returns a structure.  In the statement:
                       a = b () ;
when and how should the copying into   a   take place?

The pcc compilers I have seen apparently "set"   b   in b's stack frame.  
They then return a pointer to  b  in that frame, and copying from that 
pointer is done in  a's  frame.  But what happens if a signal comes through
during the copy?   The contents of  b  , which are not yet copied, are 
overwritten by the signal routine's stack frame?

Another compiler overcomes this problem by passing the address of a 
local structure in a's frame to the function  b  .  Thus, instead of
"setting"  b  , a's local structure is filled up, and copying from that
local structure occurs when  b  returns.

Are there other issues to be considered?

Dave Ray -- uucp:  {ucf-cs|allegra}!novavax!hcx1!daver