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error: call of overloaded âfoo(int)â is amb iguous (0 vs null ptr)
- From: "Peter A. Felvegi" <petschy at praire-chicken dot com>
- To: gcc at gcc dot gnu dot org
- Date: Thu, 24 May 2012 21:26:46 +0200
- Subject: error: call of overloaded âfoo(int)â is amb iguous (0 vs null ptr)
I'm not sure whether this is standard behaviour or not; nonetheless I
was quite surprised:
void foo(const char*);
foo(0+0); // !
foo(1-1); // !
The first call to foo() in bar() is ambiguous, all right (integral or
ptr), but the next two (marked w/ !) ? Shouldn't the compiler know that
0+0 or 1-1, etc can't be a null pointer? I tried all minor versions from
4.4 to 4.8.
Somewhat connected question: if I use |-Wzero-as-null-pointer-constant
to detect cases where 0 means null pointer, shouldn't there be a switch
that forbids conversion from 0 to null ptr? I have a class that has
operator() overloaded for size_t and for const char* (access elements by
index or by name). All is well, except for the index 0: the call would
be ambiguous. I tried to trick this with 0+0, etc, hence the whole post.
0.0 works, though. Any better ideas? Explicit cast?
Supposing that I eliminated all 0's that meant null ptr, using the
switch could eliminate this kind of ambiguity, and I could use 0 where I
mean 0, without any trickery.