https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78130
--- Comment #5 from Markus Trippelsdorf <trippels at gcc dot gnu.org> ---
markus@x4 tmp % cat string_span_tests.ii
class A {
public:
using index_type = int;
index_type m_fn1() { return size_; }
index_type size_;
};
struct B {
using element_type = int;
using index_type = int;
using pointer = element_type;
B(pointer, index_type);
void m_fn2(index_type p1) {
int a = m_fn3();
if (__builtin_expect(p1 <= a, 1))
throw;
}
index_type m_fn3() { return storage_.m_fn1(); }
A storage_;
};
struct C {
using impl_type = B;
C(impl_type);
void m_fn4() {
int b = span_.m_fn3();
span_.m_fn2(b - 1);
}
impl_type span_;
};
template <int = 0> using zstring_span = C;
struct D {
void m_fn5() const;
};
void D::m_fn5() const {
zstring_span<> c({0, 0});
try {
c.m_fn4();
} catch (int) {
}
}
markus@x4 tmp % g++ -c -O2 -Wall string_span_tests.ii
string_span_tests.ii: In member function ‘void D::m_fn5() const’:
string_span_tests.ii:14:29: warning: assuming signed overflow does not occur
when assuming that (X - c) <= X is always true [-Wstrict-overflow]
if (__builtin_expect(p1 <= a, 1))
~~~^~~~
