Re: [pdf-devel] time module unit test cases

[jemarch]

    > I disagree. Anish is talking about expecting a coherent failure
    > behaviour from a function in case you pass an invalid pointer as a
    > parameter. To check for NULL pointers in a function expecting a
    > pointer parameter is a waste of time. Most pointer variables are
    > automatic variables and thus they are not initialized to 0. In that
    > context to check for NULL is like to check for 24.
    > 
    > What makes sense and of course is mandatory is to check for a NULL
    > pointer after calling a function that _explicitly_ set the return
    > value as NULL when there is a failure or some other condition.


   Let's use an example so I get your point.

   ##

   /*
    * Test: pdf_list_create_002
    * Description:
    *   Try to create an empty list given a NULL list pointer.
    * Success condition:
    *   Returns PDF_EBADDATA
    */
   START_TEST (pdf_list_create_002)
   {
     fail_if (pdf_list_create (l_comp, l_disp, 0, NULL) != PDF_EBADDATA);
   }
   END_TEST

   ###

   Is that unit test useless? If so, I wasted a long time checking for
   NULL pointers and doing those tests. :-/ (dumb me)

Well, a check like:

   pdf_list_create (foo, bar, baz, list)
     ...
     if (list == NULL) then error PDF_EBADDATA;
     ...

would protect the function for a single case of invalid pointer. But
as I mentioned early in C there is not a way (AFAIK) to determine if a
pointer is valid or invalid. So you are covering the case list == NULL
but not list == 24 (that is likely to be an invalid address) neither
list == 25 or list == 1.

So IMHO it is not worth to check for NULL pointers inside functions
getting pointers as parameters _except_ if the function documentation
says something about a possible NULL value like:

   Parameters
     - Filesystem
         A filesystem. If NULL then the default filesystem will be used.


-- 
Jose E. Marchesi  <address@hidden>
                  <address@hidden>

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