Path: utzoo!attcan!uunet!dino!ux1.cso.uiuc.edu!castor.csg.uiuc.edu!long
From: long@castor.csg.uiuc.edu (Junsheng Long)
Newsgroups: comp.unix.questions
Subject: Help needed: Data segment layout
Message-ID: <1990Mar5.164340.7087@ux1.cso.uiuc.edu>
Date: 5 Mar 90 16:43:40 GMT
References: <5090.25e135aa@mva.cs.liv.ac.uk> <22@ctbilbo.UUCP> <666@mwtech.UUCP>
Sender: news@ux1.cso.uiuc.edu (News)
Reply-To: long@castor.csg.uiuc.edu.UUCP (Junsheng Long)
Organization: Univ of Illinois at Urbana-Champaign
Lines: 23

I would like to know the data segment layout of a C program
on Unix (Sun OS). For the following example, I found some extra 
variables were inserted before the first global variables 
(marked as ? in the following figure). 


/* --- example.c ---*/           +----------+
int a = 0;                       |  text    |
int b[32];                       +----------+ <- etext
                                 |    ?     |
main()                           +----------+
{                                |    a     |
...                              +----------+ <- edata
}                                |    b     |
                                 +----------+ <- end
                                 |          |

Now my questions are: does anyone know what they are? 
Does they vary from program to program?

Thank you very much.

junsheng long