https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107861
--- Comment #8 from Jonathan Wakely ---
(In reply to Jonathan Wakely from comment #7)
> int_max+1 is not a core constant (C++20 7.7 [expr.const] paragraph 5, bullet
oops, s/core constant/core constant expression/
> 5.7), so is not usable as
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107861
--- Comment #7 from Jonathan Wakely ---
(In reply to Markus F.X.J. Oberhumer from comment #6)
> Please note that I'm explicitly using "int_max" and not "INT_MAX",
It's a constexpr variable with the same value, so that makes no difference
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107861
--- Comment #6 from Markus F.X.J. Oberhumer ---
Please note that I'm explicitly using "int_max" and not "INT_MAX", and I'd
appreciate if you could give me a link where the standard says this is
"ill-formed". Thanks!
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107861
--- Comment #5 from Jonathan Wakely ---
To expand on that, the standard allows compilers to do anything for undefined
behaviour, including making it valid with well-defined semantics. So wrapping
for undefined overflow is a conforming
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107861
--- Comment #4 from Jonathan Wakely ---
Andrew is right. The C++ standard says this is ill-formed, the -fwrapv option
isn't allowed to change that.
The option means that runtime overflow is well-defined instead of undefined,
but that doesn't
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107861
--- Comment #3 from Markus F.X.J. Oberhumer ---
Indeed.
And just for reference I had also reported this as clang bug in
https://github.com/llvm/llvm-project/issues/59195
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107861
--- Comment #2 from Andrew Pinski ---
Note clang rejects even just:
#include
#define wrap_inc(x) ((x) + 1 < (x))
constexpr int int_max = INT_MAX;
bool b0 = wrap_inc(int_max);
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107861
--- Comment #1 from Andrew Pinski ---
Right, this is by design and I don't think it is a bug. The reasoning is the
C++ constant expressions have a way of requiring you to having to figure out if
it was going to overflow and cause different
