I am trying to convert long type variable to int type variable with uniform initialization and without it. But I get compiler warning only with uniform initialization. Why is that? Why does not gcc warn in both cases? I have tried with clang also and got similar results.
This is the code
#include <iostream>
int main() {
long l = 1;
int i1 = l;
int i2 = { l };
std::cout << i1 << std::endl;
std::cout << i2 << std::endl;
return 0;
}
And the only one warning I get
$ g++ -Wall -Wextra 1.cpp
1.cpp: In function ‘int main()’:
1.cpp:6:16: warning: narrowing conversion of ‘l’ from ‘long int’ to ‘int’ inside { } [-Wnarrowing]
int i2 = { l };
Because the standard says, narrowing conversions limit is specified only for list initialization (since C++11).
list-initialization limits the allowed implicit conversions by prohibiting the following:
- conversion from a floating-point type to an integer type
- conversion from a long double to double or to float and conversion from double to float, except where the source is a constant expression and overflow does not occur
- conversion from an integer type to a floating-point type, except where the source is a constant expression whose value can be stored exactly in the target type
- conversion from integer or unscoped enumeration type to integer type that cannot represent all values of the original, except where source is a constant expression whose value can be stored exactly in the target type
For the other initialization methods (using parentheses or equal sign), narrowing conversions limit rule is not applied (added); because that might break much legacy code.