https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80635
--- Comment #15 from Martin Sebor <msebor at gcc dot gnu.org> ---
I think the following smaller test case independent of libstdc++ captures the
same issue as the bigger test case in comment #4. Again, declaring f()
noexcept avoids the warning (but it's not a solution in general). Zero
initializing A::i first and then setting it to the result of f() also avoids
the warning and seems like more viable solution/workaround until GCC gets
smarter about exceptions.
$ cat pr80635.C && gcc -O2 -S -Wall pr80635.C
void* operator new (__SIZE_TYPE__, void *p) { return p; }
int f ();
int x;
struct A {
int i;
A (): i (f ()) { }
~A () { x = i; }
};
struct B {
B ();
~B ();
};
template <class T>
struct C {
C (): t (), b () { }
~C () { if (b) t.~T (); }
void f () {
new (&t) T ();
b = true;
}
union {
T t;
char x[sizeof (T)];
};
bool b;
};
void g ()
{
C<A> c1;
C<B> c2;
c1.f ();
c2.f ();
}
pr80635.C: In function ‘void g()’:
pr80635.C:9:13: warning: ‘c1.A::i’ may be used uninitialized in this function
[-Wmaybe-uninitialized]
9 | ~A () { x = i; }
| ~~^~~
pr80635.C:37:8: note: ‘c1.A::i’ was declared here
37 | C<A> c1;
| ^~
