Steps:
g++ -Wall ternary-ambiguous-no-error.cpp
Expected behavior:
I believe that the program below is ill-formed, because both implicit
conversions MyString <--> const char* are possible.
G++ should issue an error (or at least a warning).
>From [5.16/3]:
Using this process, it is determined whether the second operand can be
converted to match the third operand, and whether the third operand can be
converted to match the second operand. If both can be converted, or one can be
converted but the conversion is ambiguous, the program is ill-formed.
Actual behavior:
G++ doesn't report that. It chooses one of two ambiguous conversions and
compiles cleanly.
Used version:
gcc version 4.0.1 (Apple Computer, Inc. build 5363)
#include <string>
#include <iostream>
class MyString
{
public:
MyString(const char* s)
{
m_s = s;
}
operator const char*() const
{
return "surprise";
}
std::ostream &operator<<(std::ostream &os)
{
return os << m_s;
}
private:
std::string m_s;
};
int main(int argc, char* argv[])
{
bool isEmpty = false;
MyString s0("OK");
MyString s1 = (isEmpty) ? "" : s0; /* s1 is "surprise"; expected compile error
here, because both implicit conversions MyString <--> const char* are possible.
*/
std::cout << s1 << std::endl;
return 0;
}
--
Summary: Ill-formed program compiles without error. Ternary
(expr.cond) operands, ambiguous conversion.
Product: gcc
Version: 4.0.1
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: test dot 007 at seznam dot cz
GCC build triplet: i686-apple-darwin8
GCC host triplet: i686-apple-darwin8
GCC target triplet: i686-apple-darwin8
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33314
