Re: Problem upgrading c4gl to 7.20 (variable initialisation)

On Mon, 19 Oct 1998, Robert Cowham wrote: > We are recompiling an app with c4gl 7.20.UD2 and it appears to behave > differently to 6.05.UD1 in that unitialised variables are set to true whereas > previously they were set to false. GLOBAL variables and module (file static) variables are initialized to all zeroes; that's typically 0 or null. Otherwise, uninitialized local variables have whatever random garbage was left over from whatever previously used the same space. That might coincidentally have been zeroes previously and now is different, but that's why you don't rely on uninitialized variables -- you can't predict what their value will be. These rules should not have changed. Now, if your problem is with GLOBAL variables or module variables, say so, and you may yet have cause for complaint. If your problem is with local variables -- which, in my experience, is usually where this problem rears its ugly head -- then your code is faulty and that's pretty much the end of the issue. The behaviour was undefined and is still undefined and it is unfortunate that it used to work correctly and now doesn't, but the problem is still in your code, not in the product per se. I sometimes think we should have introduced a scheme whereby random values were copied into local variables deliberately to ensure that they were initialized correctly by the user, especially in p-code where the variables are actually set on entry to the function (which leads to the biggest problems when code is ported from p-code to c-code). > This has some implications for our code surprise, surprise. Has anyone else > come across this? > > Any suggestions as to an easy work around (apart from fixing the code...) such > as a compiler switch setting or whatever? No; the only real workaround is to fix the code. Yours, Jonathan Leffler (jleffler@informix.com) #include <witticism.h> Guardian of DBD::Informix v0.60 -- http://www.perl.com/CPAN Informix IDN for D4GL & Linux -- http://www.informix.com/idn