NULL v. zero [LWN.net]

NULL v. zero

Posted Jul 17, 2004 4:41 UTC (Sat) by Ross (subscriber, #4065)
In reply to: NULL v. zero by ikm
Parent article: NULL v. zero

Wait. I think I just understood what you mean:

char *bob=0*0;

would not compile as 0*0 is an integer expression. The implicit conversion
is only applied for a naked constant.

Then I retract my statement about the compiler not being able to warn in
some cases. But I continue to think this is rather strange for a language
that claims to be strongly typed. (For example the removal of implicit
conversions of char constants was a good thing... I wish C could shed that
"feature" as well.)

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NULL v. zero

Posted Jul 17, 2004 11:08 UTC (Sat) by ikm (subscriber, #493) [Link]

No,

char * bob = 0*0;

will compile. Everything that evaluates to a zero at compile time will work. That's what I actually meant by saying "zero constant". The fact that it is possible to assign various constant expressions with the zero result to pointers looks like a misfeature, but it is minor at best.

On the other hand,

int i = 0;

char * bob = i;

will not compile, as 'i' does not qualify as something that evaluates to a zero at compile time.