Re: [Valgrind-users] valgrind && sprintf arguments

[Philippe W. <phi...@sk...>]

On Mon, 2014-07-28 at 07:11 -0700, John Reiser wrote:
> > ==17454== Conditional jump or move depends on uninitialised value(s)
> > ==17454==    at 0x5921F10: strchrnul (in /lib/libc-2.11.3.so)
> > ==17454==    by 0x58E55D6: vfprintf (in /lib/libc-2.11.3.so)
> 
> > the involved fuctions are shown below; the statement in question (see below)
> > is
> > 
> >   sprintf (select_anw, sel_anw, name, name);      <********* sisisinst.c:1397
> > 
> > I have checked carefully the code and the 4 args to sprintf() are
> > all correct defined on the stack; when I change the code to:
> > 
> > 
> >   select_anw[0] = '\0';
> >   sprintf (select_anw, sel_anw, name, name); 
> > 	
> > then is valgrind happy, i.e, does not raise the messages any more;
> 
> You say that all 4 args are on the stack.  What are their actual addresses?
> Run with --db-attach=yes, say 'y' when asked, and use gdb to look around.
--db-attach=yes should be considered as (is?) obsolete.

You could instead use --vgdb-error=1 (to just attach when the error is
reported) or better use --vgdb-error=0, put breakpoints
and verify the (un-)definedness of the relevant variables at various
points between their declaration and their usage.

Philippe