Xref:	news2.mv.net comp.os.msdos.djgpp:8592
From:	Thomas Nilsson <thoni AT softlab DOT se>
Newsgroups:	comp.os.msdos.djgpp
Subject:	Possible static data zeroisation bug in DJGPP v2?
Date:	Fri, 13 Sep 1996 19:23:43 +0200
Organization:	SoftLab
Lines:	43
Message-ID:	<3239989F.4626@softlab.se>
NNTP-Posting-Host:	rabbit.softlab.se
Mime-Version:	1.0
To:	djgpp AT delorie DOT com
DJ-Gateway:	from newsgroup comp.os.msdos.djgpp

I have an application which I mainly develop on Unix, however thanks to
the wonderful DJGPP it's very easy to port to PC's, thanks all who have
contributed in the DJGPP project!!

However I have stumbled upon a problem:

In one of the modules I have a static structure that is essential to the
output from the program. Somehow it is not zeroised correctly, or of
course it could be overwritten by some other part of the program. I
decided to investigate and started 'gdb' a debugger which I am much
familiar with from the Unix environment.

IT WON'T LET ME SEE THE STRUCTURE UNTIL I ENTER A FUNCTION WHICH USES
IT. 

The structure is declared static at the top level of the module and in
the beginning of the file, but still gdb says 'No symbol xxxx in current
context'. The structure *should* not be used before that point in the
running of the program, but it is not zero as I would have expected.

This being strange, but still I wanted to investigate this structure, so
I removed the static declaration to make it more visible, and thought
that I might get at it already at the start of the program. And of
course I could, *but* now it is zeroised correctly and not destroyed so
the program works perfectly...

Is this a bug, or if not, how do I find out when the structure is
trashed. Note however that Purify (a lovely memory access analyser for
many plattforms) does not indicate any problems on Unix (so at least
it's not a general bug, but then which ones are...)

/Thomas


-- 
"Little languages go a long way..."
(ThoNi of ThoNi&GorFo Adventure Factories in 1985)
------------------------------------------------------------------------
Thomas Nilsson				Phone Int.: (+46) 13 12 11 67
Stenbrötsgatan 57			Phone Nat.: 013 - 12 11 67
S-582 47 LINKÖPING 			Email: thoni AT softlab DOT se
SWEDEN					alan-request AT softlab DOT se for info
------------------------------------------------------------------------

- Raw text -