------- Comment #6 from l dot lunak at suse dot cz 2008-03-23 20:16 ------- > Hmm, 2*0.5 should be folded pretty early so Wconversion should see 1.0 which > can be converted exactly to an integer (I think), so there should be no > warning whatsoever. Are you sure you are using GCC 4.3? I cannot reproduce > the warning.
I didn't realize gcc could optimize this example. It was just meant to be an example of passing any float to foo(int). Make that foo(M_PI*10), foo(1.2), foo(sin(bar)*100) or whatever. My point was that calling foo(int) as foo(var) with var being a float is quite common code, whereas foo(NULL) is a mistake (or brain-damage :) ). Therefore I'd like a way to get warned only about the latter but not the sooner, which -Wconversion is not. That is why I changed this to an enhancement after being told that -Wall not warning about foo(NULL) is not a bug. > > True. So, is there any example where use of NULL / __null in a non-pointer > > context is a good idea? > > Is there an example where it leads to bugs? Yes. Consider you have code like this: void foo(void* bar); // a function somewhere ... foo( NULL ); // you call it ... Now consider you want to add an overload foo(int). Now everybody who called the original version as foo(0) is suddenly calling a different function, but I intentionally used NULL to express I'm passing a null pointer, so I expect at least a warning (and without all the stuff I'd get with -Wconversion). And this example is actually based on a real problem that I had to debug in KDE libraries. -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=35669
