Date:	Fri, 13 Sep 1996 16:50:55 -0700 (PDT)
From:	Samuel Vincent <svincent AT cs DOT sonoma DOT edu>
To:	Thomas Nilsson <thoni AT softlab DOT se>
cc:	djgpp AT delorie DOT com
Subject:	Re: Possible static data zeroisation bug in DJGPP v2?
In-Reply-To:	<3239989F.4626@softlab.se>
Message-ID:	<Pine.GSO.3.94.960913164939.26825C-100000@zippy>
MIME-Version:	1.0

On Fri, 13 Sep 1996, Thomas Nilsson wrote:

> 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...)


rather than just doing a:

static struct whatever mystruct;

since you want it zeroed, you are doing this, correct?

static struct whatever mystruct = { 0 };




-Sam

- Raw text -