Some subsurface notes from a week of diving

[Thiago Macieira]

Em seg 17 mar 2014, às 08:31:05, Linus Torvalds escreveu:
> > +static inline int number_of_computers(struct dive *dive)
> > +{
> > +       int total_number = 0;
> > +       struct divecomputer *dc = &dive->dc;
> > +
> > +       if (!dive)
> > +               return 1;
> > 
> > (hint: think what happens if dive == null)
> 
> Absolutely nothing happens.

Actually, the compiler is allowed in this case to assume that dive is never 
null.

Doesn't matter that you didn't actually dereference the memory location. It's 
still undefined behaviour to do what you've done.

The offsetof macro notwithstanding, since that is provided by the compiler and 
can be implemented through a builtin. And it is:

$ gcc -dM -E -include stddef.h -xc /dev/null | grep offsetof
#define offsetof(TYPE,MEMBER) __builtin_offsetof (TYPE, MEMBER)

-- 
Thiago Macieira - thiago (AT) macieira.info - thiago (AT) kde.org
   Software Architect - Intel Open Source Technology Center
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