[Bug c++/85827] false positive for -Wunused-but-set-variable because of constexpr-if
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=85827 Marek Polacek changed: What|Removed |Added Status|ASSIGNED|RESOLVED Resolution|--- |FIXED --- Comment #6 from Marek Polacek --- Done.
[Bug c++/85827] false positive for -Wunused-but-set-variable because of constexpr-if
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=85827 --- Comment #5 from Marek Polacek --- Author: mpolacek Date: Fri Aug 16 20:40:36 2019 New Revision: 274587 URL: https://gcc.gnu.org/viewcvs?rev=274587=gcc=rev Log: PR c++/85827 g++.dg/cpp1z/constexpr-if29.C: New test. Added: trunk/gcc/testsuite/g++.dg/cpp1z/constexpr-if29.C Modified: trunk/gcc/cp/ChangeLog
[Bug c++/85827] false positive for -Wunused-but-set-variable because of constexpr-if
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=85827 Marek Polacek changed: What|Removed |Added Status|NEW |ASSIGNED Assignee|unassigned at gcc dot gnu.org |mpolacek at gcc dot gnu.org --- Comment #4 from Marek Polacek --- This particular problem was fixed in r269433, because the condition is not dependent. I'll add the test. For another problem not fixed by this rev see PR81676.
[Bug c++/85827] false positive for -Wunused-but-set-variable because of constexpr-if
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=85827
--- Comment #3 from Matthias Kretz ---
But macros are different. They remove the code before the C++ parser sees it
(at least as-if). One great improvement of constexpr-if over macros is that all
the other branches are parsed and their syntax checked. E.g. it requires the
mentioned names to exist. This doesn't compile (cf.
https://godbolt.org/g/iCRPDv):
#ifdef HAVE_FOO
constexpr bool have_foo = true;
void foo();
#else
constexpr bool have_foo = false;
#endif
void f() {
if constexpr (have_foo) {
foo();
}
}
So, the frontend parses all branches anyway. It should be able to see that _2
and _3 are referenced in f<1>().
[Bug c++/85827] false positive for -Wunused-but-set-variable because of constexpr-if
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=85827 --- Comment #2 from Marc Glisse --- I think that's going to be hard. The same issue always existed with macros. The whole point of "if constexpr" is not to look at the other branches, as they may not even compile. Sure, some minimal "safe" attempt at looking at those branches would be possible, but I am not sure it is worth the trouble.
[Bug c++/85827] false positive for -Wunused-but-set-variable because of constexpr-if
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=85827 Jonathan Wakely changed: What|Removed |Added Keywords||diagnostic Status|UNCONFIRMED |NEW Last reconfirmed||2018-05-18 Ever confirmed|0 |1
[Bug c++/85827] false positive for -Wunused-but-set-variable because of constexpr-if
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=85827 --- Comment #1 from Matthias Kretz --- Same issue for -Wunused-variable
