[Bug c/31887] bad warning converting qualified void* to qualified array pointer

[raeburn at raeburn dot org]

------- Comment #2 from raeburn at raeburn dot org  2007-05-11 08:05 -------
Subject: Re:  bad warning converting qualified void* to qualified array pointer

On May 10, 2007, at 19:00, pinskia at gcc dot gnu dot org wrote:
> I think only "void*" can be done with an implicat cast so we go  
> from const
> void* to void* and then to const block*.

ISO/IEC 9899-1999 section 6.5.16.1 (assignment constraints) includes:

  - one operand is a pointer to an object or incomplete type and the  
other is a pointer to a qualified or unqualified version of void, and  
the type pointed to by the left has all the qualifiers of the type  
pointed to by the right.

So I'm pretty sure we don't automatically lose on the const-ness in  
the general case.  What I'm less sure about is how the array type  
plays into it.  According to 6.7.3, "const block" means "array [8] of  
const unsigned char", so is there an argument to be made that  
assigning a pointer-to-const value to an lvalue of type pointer to an  
unqualified array type (containing a type that happens to be const- 
qualified) isn't allowed?  I don't think it would be logical, but  
that doesn't guarantee that that's how the standard actually works.

Ken


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=31887