Xref: utzoo comp.lang.c:30482 gnu.gcc:1797
Path: utzoo!utgpu!watserv1!watmath!uunet!unhd!al
From: al@uunet!unhd (Anthony Lapadula)
Newsgroups: comp.lang.c,gnu.gcc
Subject: Local Variable Storage Scope
Message-ID: <1990Jul23.230418.15169@uunet!unhd>
Date: 23 Jul 90 23:04:18 GMT
Distribution: na
Organization: Computing Information Services, University of New Hampshire
Lines: 22

I've found some interesting behaviour in our current C compiler (gcc 1.36).

   void f()
      {
           {  int local1[100]; /* some code goes here */  }
           {  int local2[100]; /* more code goes here */  }
      }


Is the compiler allowed to allocate just enough space for only
one of the local arrays?  That is, can ``local1'' and ``local2''
share the same spot on the run-time stack?

Gcc does *not* do this, but instead reserves enough room on the
stack for both arrays.  I couldn't come up with an explanation
for this behaviour.  Is there one?

BTW, the code in question is being generated by another program.
*Lots* of local arrays are declared, but the code must run on a
machine with 512K RAM and no VM -- so every bit of stack space helps.

-- Anthony (uunet!unhd!al) Lapadula