Re: [Tinycc-devel] tcc_relocate() and tcc_relocate_ex()

[Sean Conner]

It was thus said that the Great grischka once stated:
> Sean Conner wrote:
> >>As to the patch I think that
> >>    +    s1->runtime_mem = NULL;
> >>would break tcc_relocate and I don't see why you need it.
> >
> >  I did that so that the call to tcc_delete() wouldn't crash when it tried
> >to free s->runtime_mem that might contain a garbage value (since
> >tcc_relocate_ex() would never set that field).  Good thing too, because
> >tcc_new() *might not* be initializing NULL pointers correctly [1].
> 
> Well, from my point of view that line would not fix tcc_new
> but cause a memory leak for tcc_relocate.

  I did a bit more work.  The assignment of s1->runtime_mem to NULL does not
lead to any memory leaks.  On systems where the NULL pointer *is* all zeros
(most, if not all, modern systems I am aware of) removing the assignment
does not cause a crash (since the memory used to store the state is zeroed
out).  On systems where the NULL pointer *IS NOT* all zeros [1], removing
the assignment *WILL CRASH*.  Not "might crash", *WILL CRASH*. [2]

  -spc

[1]     Remember, ANSI C states that a literal 0 in the source code in a
        pointer context is converted to a "NULL" pointer.  Said "NULL"
        pointer does not have to be 0.

[2]     Okay, so I had to force the issue by hanging the assignment to a
        bogus address that was not 0.