CODEWITHSUNDEEP
c++castingdefaultimplicitexplicit
Jean-Luc Nacif Coelho
Jean-Luc Nacif Coelho

Reputation: 1022

C++ how do i keep compiler from making implicit conversions when calling functions?

Here's the deal:

When i have a function with default arguments like this one

int foo (int a, int*b, bool c = true);

If i call it by mistake like this:

foo (1, false);

The compiler will convert false to an int pointer and call the function with b pointing to 0.

I've seen people suggest the template approach to prevent implicit type conversion:

template <class T>
int foo<int> (int a, T* b, bool c = true);

But that approach is too messy and makes the code confusing.

There is the explicit keyword but it only works for constructors.

What i would like is a clean method for doing that similarly to the explicit method so that when i declare the method like this:

(keyword that locks in the types of parameters) int foo (int a, int*b, bool c = true);

and call it like this:

foo (1, false);

the compiler would give me this:

foo (1, false);
         ^
ERROR: Wrong type in function call (expected int* but got bool)

Is there such a method?

Upvotes: 4

Views: 1475

Answers (2)

BЈовић
BЈовић

Reputation: 64223

The best way is to set the warning level properly, and not ignore warnings.

For example gcc, has the -Wall option, which handles lots of problematic cases, and will show next warning in your case (g++ 4.8.1):

garbage.cpp: In function ‘int main(int, char**)’:
garbage.cpp:13:13: warning: converting ‘false’ to pointer type for argument 2 of ‘int foo(int, int*, bool)’ [-Wconversion-null]
  foo(0,false);

Upvotes: 3

ForEveR
ForEveR

Reputation: 55887

No, there is no such method. Template is good for such thing, I think. However, in gcc for example there is flag -Wconversion-null, and for code with foo(1, false) it will give warning

converting «false» to pointer type for argument 2 of «int foo(int, int*, bool)» [-Wconversion-null]

and in clang there is a flag -Wbool-conversion

initialization of pointer of type 'int *' to null from a constant boolean expression [-Wbool-conversion]

Upvotes: 5

Related Questions