https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102048
Bug ID: 102048
Summary: __gnu_cxx::rope.erase(size_t __p) implementation seems
to be wrong
Product: gcc
Version: 12.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: libstdc++
Assignee: unassigned at gcc dot gnu.org
Reporter: fstqwq at foxmail dot com
Target Milestone: ---
In ext/rope from all versions of gcc I could refer to (see
https://github.com/gcc-mirror/gcc/blame/master/libstdc%2B%2B-v3/include/ext/rope#L2407,
the last change is made 17 years ago), the implementation of
__gnu_cxx::rope.erase(size_t) is:
// Erase, single character
void
erase(size_type __p)
{ erase(__p, __p + 1); }
The comment said it will erase a single character from rope. However, the
function actually erase (__p + 1) characters starting from position __p by
calling erase(size_t, size_t) commented as "Erase, (position, size) variant.",
which is just defined above the erase(size_t) version.
You can test the function by the following code:
#include <bits/stdc++.h>
#include <ext/rope>
int main() {
__gnu_cxx::rope<int> R;
for (int i = 0; i < 9; i++) R.push_back(i);
R.erase(2);
for (int i = 0; i < 4; i++) std::cout << R[i] << std::endl;
}
If erase functions normally or replace erase(2) with erase(2, 1), it's expected
to see 0 1 3 4. It turned out to be 0 1 5 6, that erases 3 elements starting
from 2.
