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From: ericf@uwvax.UUCP (Eric Feigenson)
Newsgroups: net.micro,net.micro.16k,net.micro.pc
Subject: Re: MS-DOS object code format
Message-ID: <678@uwvax.UUCP>
Date: Tue, 4-Mar-86 10:39:14 EST
Article-I.D.: uwvax.678
Posted: Tue Mar  4 10:39:14 1986
Date-Received: Wed, 5-Mar-86 06:27:27 EST
References: <549@imag.UUCP>
Organization: U of Wisconsin CS Dept
Lines: 33
Keywords: MS-DOS, object code, linker input
Xref: watmath net.micro:13968 net.micro.16k:441 net.micro.pc:7282
Summary: Experience with MS-DOS object file formats

While someone is looking for a reference to MS-DOS object file formats...

I recently was trying to analyze the .OBJ files under MS-DOS.  I got
the "8086 Relocatable Object Module Formats" document from Intel
(Order number 121748-001) to aid me in my quest.  However, there
seems to be a critical difference in the .OBJ format described in the
document, and the .OBJ files I found generated by the Microsoft C Compiler.
It's been a while (I got frustrated, and gave up for a while), but the
gist of the difference is the following:  There are two record types in 
an object module that describe global data, EXTDEF (for globals referenced
in the module, but not allocated space there) and PUBDEF (for globals
defined in the module).  What I found was that there were symbols that
were defined in the module (i.e., space was allocated for them there)
that appeared in EXTDEF records (which implies that they were *not*
allocated in the module, and the linker would need to find the module
where the symbols *are* defined).  Since I am mainly trying to find
out what symbols are external vs. public in a module, this is a very
annoying situation.

Can anyone shed any light on this?  Have I overlooked something?  Is
the Intel document describing something different than is dealt with
with the Microsoft C Compiler and Linker?  Could a global symbol appear
in an EXTDEF *and* PUBDEF record?  If necessary, I can produce a .OBJ
that exhibits this problem (no really, it does happen... I'm *not* crazy...)

Thanks!

-- 

				    -Eric Feigenson

				    Usenet: {seismo, allegra, ihnp4}!uwvax!ericf
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