https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109737
Bug ID: 109737
Summary: [13/14] Hitting unreachable code when using
std::string::assign with iterators
Product: gcc
Version: 13.1.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: libstdc++
Assignee: unassigned at gcc dot gnu.org
Reporter: enrico.seiler+gccbugs at outlook dot com
Target Milestone: ---
The following emits "runtime error: execution reached an unreachable program
poin" when compiling with `-g -fsanitize=undefined -std=c++20`:
```
#include <cassert>
#include <sstream>
#include <string>
void fits_in_local_buffer()
{
std::stringstream source{"123457890123456"};
std::string str;
str.assign(std::istreambuf_iterator<char>{source},
std::istreambuf_iterator<char>{});
assert(str == "123457890123456");
}
void does_not_fit_in_local_buffer()
{
std::stringstream source{"1234578901234567"};
std::string str;
str.assign(std::istreambuf_iterator<char>{source},
std::istreambuf_iterator<char>{});
assert(str == "1234578901234567");
}
int main()
{
fits_in_local_buffer(); // OK
does_not_fit_in_local_buffer(); // Not OK
return 0;
}
```
Compiler Explorer: https://godbolt.org/z/6obr7afon
* Must be at least compiled with CPP20
* Using std::string's constructor with the iterators works.
* Unreachable was introduced with PR109299
https://github.com/gcc-mirror/gcc/commit/bf78b43873b0b7e8f9a430df38749b8b61f9c9b8
* The std::istreambuf_iterator is used as an example, but the same happens when
using, for example, a std::views::iota and using its iterators
