On 27/08/07, Joshua Isom <[EMAIL PROTECTED]> wrote: > > On Aug 27, 2007, at 11:13 AM, Paul Cochrane (via RT) wrote: > > > # New Ticket Created by Paul Cochrane > > # Please include the string: [perl #44995] > > # in the subject line of all future correspondence about this issue. > > # <URL: http://rt.perl.org/rt3/Ticket/Display.html?id=44995 > > > > > > > Hi everyone, > > > > Another issue raised by Coverity Prevent[1] is that of a NULL pointer > > being dereferenced. This occurs as a result of the following code > > (from src/dynoplibs/myops.ops:54): > > > > int *a, i; > > a = NULL; > > i = *a; > > > > Note that i is assigned to *a which is set to NULL. Coverity picks > > this up as being a bad thing. Should this be > > > > a = NULL; > > i = NULL; > > > > ?? > > > > The reason I send this question to the list rather than just "fixing" > > the issue is because whenever pointers are involved I get nervous and > > like to seek the help of higher intelligences than myself. > > > > - is the original code ok? If not, how should it be changed to be > > safe? > > - is Coverity just throwing up a false positive? > > - what is the meaning of assigning NULL to a variable (which is > > declared as a pointer) and then using that to initialise another > > variable which *isn't* a pointer. This is a fine point, and is > > therefore where I'm lacking knowledge as to what exactly the code > > means. > > > > Many thanks to anyone who helps me out on this! > > > > Paul > > > > [1] For those with Coverity Prevent accounts, see CIDs 80, 81, 82 > > > > > > I recall this problem. If you look at the documentation above the > code, it says "Halt and Catch Fire. Tries to crash parrot." Instead of > a simple dereferencing null, some compilers optimize away unused code > so it was rewritten to guarantee it would dereference a null pointer.
Mehmet and Joshua, I can't believe I missed the comment! How embarassing....! Thanks heaps to you both for pointing that out for me :-) Paul
