How do conversion operators work in C and when does the compiler use them for type substitution?

Conversion Operators in C

Question: How do conversion operators work in C , and when does the compiler attempt to substitute the type defined after the conversion operator?

Answer: Conversion operators in C facilitate type conversions between classes or from classes to fundamental types. The compiler substitutes the type specified after the conversion operator in the following situations:

Conversion during Argument Passing:

• During argument passing, the rules for copy initialization apply, considering any conversion function regardless of whether it converts to a reference or not.
• Example: void f(B); int main() { f(A()); }

Conversion to Reference:

• In conditional operators, conversion to a reference type is possible if the type being converted to is an lvalue.
• Example: B b; 0 ? b : A();

Conversion to Function Pointers:

• Conversion functions to function pointers or references can be used when a function call is made.
• Example: typedef void (*fPtr)(int); void foo(int a); struct test { operator fPtr() { return foo; } };

Conversion to Non-Class Types:

• User-defined conversion functions can be used for implicit conversions involving non-class types.
• Example: struct test { operator bool() { return true; } };

Conversion Function Templates:

• Templates can be used to create conversion functions that allow a type to be convertible to any pointer type.
• Example: struct test { template operator T*() { return 0; } };
• Caution: These should be used cautiously as they can lead to ambiguous conversions.

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