My compiler warms me about a lot of implicit conversion:
Some I do understand, like
implicit conversion changes signedness: 'int' to 'std::vector::size_type' (aka 'unsigned long')`
when I do myvector.resize(myInt) .
Other more obscure, like
implicit conversion loses integer precision: 'std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >::size_type' (aka 'unsigned long') to 'int'
when I do myInt=myString.size(), or
implicit conversion changes signedness: 'int' to 'std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >::size_type' (aka 'unsigned long')
when I call myString[myInt]
I all cases, I do understand why I get these message (int-uint, etc), however their use is non-ambiguous in the program. What do I risk if I do not hunt change the type of my variables to delete these warning? My previous compiler didn't warn me of anything, so when I changed my PC I suddenly had dozens of warning.
I all cases, I do understand why I get these message (int-uint, etc), however their use is non-ambiguous in the program. What do I risk if I do not hunt change the type of my variables to delete these warning?
It's not about ambiguity. If you convert a signed value to an unsigned type, you may get bizarre results:
long i = -2147483645; // for example
std::vector<int> vec{0, 1, 2, 3, 4};
std::cout << vec[i] << "\n"; // undefined behavior, not always caught
Here, assuming a 32-bit system, i gets converted to 2147483651 before it is passed to operator[], causing undefined behavior.
If you are really sure the conversion is harmless, you can do a static_cast:
static_cast<std::vector<int>::size_type>(i)
My previous compiler didn't warn me of anything, so when I changed my PC I suddenly had dozens of warning.
Always turn on warnings. At least do -Wall. When writing libraries, I tend to make sure my code compiles cleanly even with -Wextra. They can help you catch a lot of bugs.