https://gcc.gnu.org/bugzilla/show_bug.cgi?id=69818
Frank Heckenbach <f.heckenb...@fh-soft.de> changed:
What |Removed |Added
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CC| |f.heckenb...@fh-soft.de
--- Comment #8 from Frank Heckenbach <f.heckenb...@fh-soft.de> ---
Some such cases, including the original example, will run afoul of aliasing
rules and at least produce a warning about that.
However, that's not the case when the target is char &, since char is
explicitly allowed to alias. So here's an example that doesn't produce any kind
of warning with any option I tried:
#include <iostream>
int main ()
{
float x = 1.2345f;
using T = char &;
std::cout << +T (x);
}
It outputs 25 on x86_64 (LE) rather than 1 as with a value cast to char.
I agree that it may occur unnoticed in generic programming where a type
parameter may easily become of reference type.
I don't see any reason why someone would intentionally want to use this
"feature" -- if one wants a reinterpret cast, one should write
reinterpret_cast.
So I agree a warning would be very useful -- I'd even say it should be included
in -Wall or -Wextra if not on by default.
See also:
https://quuxplusone.github.io/blog/2020/01/22/expression-list-in-functional-cast/
