http://llvm.org/bugs/show_bug.cgi?id=16773
Bug ID: 16773
Summary: Copy initialization using conversion operator does not
find correct candidates for initialization of final
result
Product: clang
Version: 3.2
Hardware: PC
OS: Windows NT
Status: NEW
Severity: normal
Priority: P
Component: C++
Assignee: [email protected]
Reporter: [email protected]
CC: [email protected], [email protected]
Classification: Unclassified
I have a reduced test case.
MSVC seems to work fine (online compiler test: http://rise4fun.com/Vcpp/2sQ).
The copy initialization of an object of type A from a class object of type
C is expected to find C::operator B &() as the function selected by overload
resolution.
The result of the call, an lvalue of type B, is then used to direct-initialize
the object that is the destination of the copy-initialization.
See C++11 subclause 8.5 [dcl.init] paragraph 16.
Note that the result of the call is specified to be used, not the result of the
user-defined conversion sequence which was considered for overload resolution.
The direct initialization from the lvalue of type B has for its candidates all
of the constructors for A (13.3.1.3 [over.match.ctor]).
Note that A(B &) has a standard conversion sequence from the lvalue of type B
to
its sole argument (the identity conversion).
clang++ seems to be fixated with the copy constructors for A instead of using
overload resolution for the direct initialization.
## Self-contained test case (main.cpp):
struct B;
struct A {
A();
A(const A &, bool = 0);
A(const A &, short = 0);
A(B &);
};
struct B : A { };
struct C {
operator B &();
};
int main() {
C c;
A a = c;
}
## Compiler invocation:
clang++ '-std=c++11' -c main.cpp
## Compiler output:
main.cpp:17:6: error: ambiguous constructor call when copying variable of type
'B'
A a = c;
^ ~
main.cpp:4:4: note: candidate constructor
A(const A &, bool = 0);
^
main.cpp:5:4: note: candidate constructor
A(const A &, short = 0);
^
1 error generated.
## Expected behaviour:
Clean compile.
## clang++ -v:
clang version 3.2 (trunk 158227)
Target: i386-pc-cygwin
Thread model: posix
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