When you execute all features of your application, this gives you the maximum sp value that has been reached by your application. Make sure that your assumptions about the available stack are correct. Some 8051 variants have just 128 bytes on-chip RAM and therefore the stack space ends at ...
std::__1::allocator<long>, void>(std::__1::allocator<long> const&, unsigned long) /opt/compiler-explorer/clang-trunk-20231002/bin/../include/c++/v1/__memory/shared_ptr.h:1301:12