Layout of Structs (J. A. Chandross)
28 May 89 02:06:27 GMT

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Layout of Structs (1989-05-28)
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From: (J. A. Chandross)
Newsgroups: comp.compilers
Keywords: symbol tables, offsets, psects, real-time monitor
Date: 28 May 89 02:06:27 GMT
References: <>
Distribution: na
Organization: Rutgers Univ., New Brunswick, N.J. (Rick 'Transputer' Stein)
> I have some questions about how a compiler constructs a symbol table.
> [questions on structure layout deleted]

Our erstwhile moderator replies:
> C compilers have the right to lay out structures any way they see fit,
> unless the ANSI committee changed the rules.

I quote, without permission, from The Bible, page 196, First Edition:

"Within a structure, the objects declared have addresses which increase
as their declarations are read lef-to-right. Each non-field member of
a structure begins on an addressing boundry appropriate to its type;
therefore, there may be unnamed holes in a structure. Field members
are packed into machine integers; they do not straddle words. A field
which does not fit into the space remaining in a word is put into the
next word....."

It is a Good Thing [tm] that structures are laid out in this way. As
a hardware type, I often need to write device drivers. Being able to
impose a structure onto a hardware memory map is a very useful thing,

Jonathan A. Chandross
UUCP: rutgers!!jac
[I hope I'm not the erstwhile moderator yet, but stand corrected. -John]

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