structure function returns -- how?

[notes at hcx1.UUCP]

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