https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115180
Bug ID: 115180
Summary: [regression] free-nonheap-object on std::vector usage
Product: gcc
Version: 14.1.1
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: gene at staubsaal dot de
Target Milestone: ---
Compiler: gcc (GCC) 14.1.1
Compile flags: -std=c++20 -O3 -Wfree-nonheap-object
The following code produces an "-Wfree-nonheap-object" warning, which doesn't
happen with '-O2' or using an older version of gcc.
This seems to be a false warning. (Or maybe even some false optimization going
on?)
```
#include <cassert>
#include <vector>
// Since K+1 the returned vector has size() >= 1
inline auto f(size_t N, size_t K) {
return std::vector<std::vector<size_t>>(K+1, std::vector<size_t>(N, 0));
}
// create another vector, but derive size from the previous vector
inline auto g(std::vector<std::vector<size_t>> const& v1) {
size_t const K = v1.size() - 1;
size_t const N = v1[0].size();
return std::vector<std::vector<size_t>>(K+1, std::vector<size_t>(N, 0));
}
struct S {
std::vector<size_t> v1;
std::vector<size_t> v2;
// v1, v2always have the same length
};
auto h(size_t N, size_t K) {
assert(N>0);
assert(N >= K);
auto v1 = f(N, K);
auto v2 = g(v1);
auto ss = std::vector<S>{};
for (size_t i{0}; i < v1.size(); ++i) {
ss.emplace_back(S{v1[i], {}});
}
for (auto& s : ss) {
s.v1.back() += 1;
}
return ss;
}
auto all = h(4, 3);
```
For convenience a link to godbolt: https://godbolt.org/z/dPj1YYf7x
