https://gcc.gnu.org/bugzilla/show_bug.cgi?id=89337
Martin Sebor <msebor at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Keywords| |diagnostic
Status|UNCONFIRMED |RESOLVED
CC| |msebor at gcc dot gnu.org
Blocks| |88443
Resolution|--- |INVALID
--- Comment #2 from Martin Sebor <msebor at gcc dot gnu.org> ---
In the test case from attachment 45704:
struct sstring {
size_t _size;
sstring(size_t size) : _size(size) { memset(begin(), '\n', size); }
size_t size() const noexcept { return _size; }
void resize(size_t n) {
if (n > size()) {
sstring x(n - size());
}
}
char *begin();
};
void drop3(sstring &name) { name.resize(name.size() - 3); }
GCC can't see that drop3() cannot be called with name.size() < 3, and in
resize, the condition (n > size()) can only be true only when name.size() < 3
so n - size() is unavoidably too large.
To avoid the warning make the precondition explicit:
void drop3(sstring &name)
{
if (name.size () < 3)
__builtin_unreachable ();
name.resize(name.size() - 3);
}
Referenced Bugs:
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=88443
[Bug 88443] [meta-bug] bogus/missing -Wstringop-overflow warnings
