Uniform initialization syntax or type conversion?

Question

Changing the parens to curly braces seems to produce the exact same behavior in my program, even though semantically they seem to be quite different beasts. Is there a reason (memory usage, performance, etc.) to prefer one?

double pie = 3.14159;

myVal = int(pie); // type conversion using operator()
myVal = int{pie}; // uniform initialization syntax

[edit]

My actual code is a little different from the above example, perhaps that explains the narrowing issues:

int32_t result;

myVal = uint16_t(result);  // myVal is between 0 and 65535
myVal = uint16_t{result};  // myVal is between 0 and 65535

Answer 1

First note that what you are doing there is not initialization, is a type conversion followed by an assignment. I strongly recommend C++ casting operators (static_cast in this case) over C casts and these constructor-based castings.

That said, the main difference between uniform initialization and the other is that uniform initialization doesn't allow (See the note) narrowing conversions such these you are doing, float to int. This is helpful when writting constants or initializing variables, since initializing an int with 3.141592654 has no sense at all because the fractional part will be stripped out.

NOTE: I remember the initial proposal for uniform-initialization explicitly stating that it disallows narrowing conversions, so if I had understood it correctly, code like yours should not compile.
I have tested it and seems like compilers emmit warnings about the narrowing conversions instead of aborting compilation. Indeed, that warnings are useful too, and you could allways use a -Werror flag.