Re: Fun with std::string::operator(char c)

From:

Alan Woodland <ajw05@aber.ac.uk>

Newsgroups:

comp.lang.c++

Date:

Fri, 21 Aug 2009 18:49:19 +0100

Message-ID:

<d433m6x9m3.ln2@news.aber.ac.uk>

Francesco wrote:

On 21 Ago, 16:51, itroot <ivan.tolstoshe...@gmail.com> wrote:

Hello,
how can i make g++ show me warning when such implicit casting occurs?

#include <iostream>
#include <string>

int main() {
  int x=10;
  std::string s;
  s=x; // int implicitly assigned to char, then called
std::string::operator=(char)

}

This piece of code really surprise me, and i'cant found how i can make
g++ warn me.
I want warning on each "narrowing" conversion as char c=(int)(2), etc.
Thanks.

I've stomped on the same issue - and it surprised me just in the same
way.

I think you'll have to live with it, that's a standard, legal
conversion which is explicitly allowed to lose data, I don't think
there is any way to force a compiler warning - somebody else will
eventually correct this statement of mine, shall it be false.

If it's for code that you're writing rather than STL or other 3rd party
code you can always do:

void f1(char c);
void f2(char& c);

int main() {
   int x=10;
   f1(x);
   f2(x); // Will fail

   return 0;
}

I can't think of a conforming way to make your example emit either an
error or warning though.

Alan