1. Implicit type conversion and copy constructor
If you want to define your own copy constructor, you should define like that:
class Foo {
public:
Foo (const Foo& obj) {}
};
Pay attention to the const in the parameter declaration. If your copy constructor definition loses const (Sun’s C++ compiler does NOT complain), your implicit type conversion member will fail to compile, though the copy constructor is not used in type conversion.
class Foo {
public:
Foo (Foo& obj) {}
Foo (Bar *obj) {}
};
Foo test () { return new Bar(); }
On linux with g++, you will get the error messages as following:
error: no matching function for call to ‘Foo::Foo(Foo)’
… …
error: initializing temporary from result of ‘Foo::Foo(Bar*)’
On solaris with sun studio c++ compiler, you will get:
Error: Cannot use Bar* to initialize Foo without "Foo::Foo(const Foo&)"
2. The reference of pointer and "this"
Look at this piece of code:
void test (Foo* &obj) {}
//void test (Foo* const &obj) {}
class Foo {
public:
void bar () { test (this); }
};
On linux with g++, you will get error messages as following:
invalid initialization of non-const reference of type ‘Foo*&’ from a temporary of type ‘Foo* const’
in passing argument 1 of ‘void test(Foo*&)’
On solaris with sun studio c++ compiler, you will get:
Error: Formal argument obj of type Foo*& in call to test(Foo*&) requires an lvalue.
Seems that sun studio c++ compiler treats the & in "&obj" as the addressing operator, so it requires an lvalue (left value). If we uncomment the 2nd test () (which in blue), then in function bar (), we must call test ((Foo *const) this); or just comment out the 1st test (), so that we could pass the compiling.
For non const members or external functions, the type of ‘this’ is Foo *const, for const members, its type is const Foo *const.
).
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