[GiNaC-devel] Compiler-dependent bug with nested lists

Dear GiNaC developers, I noticed a strange bug, which only happens with some compiler versions. In some cases, nested lists collapse into a flat list. Consider the following program:

#include <iostream> #include "ginac/ginac.h"

using namespace GiNaC; int main(int argc, const char** argv) {     std::cout << lst{lst{1}} << std::endl;     return 0; }

I tested this with GCC 11.4.0 and clang 21.1.0. With those compilers, it correctly prints

{{1}}

But with clang 19.1.7, it instead yields

{1}

I tested some other cases and it seems that the issue occurs whenever a list has a single element which is also a list. Best regards Florian