[derSteFfi]

Guarder resolves the real pthread_create with dlopen("libpthread.so.0", RTLD_NOLOAD). Since glibc 2.34 that library is an empty compatibility stub that nothing loads, so the handle comes back NULL and dlsym(NULL, name) searches the global scope from the front - which finds guarder's own interposer. Every pthread_create() then recursed into itself until the 128-entry thread table was full and guarder aborted with "maximum concurrent thread limit reached (128)"; an interposer mounted in front of libguarder.so counts 128 creations and no joins for "./mstress 4 50 25". That is the mstressN and rptestN failure in the gd jobs on ubuntu and fedora, and with the fallback both return to exit 0. RTLD_NEXT starts the search after libguarder.so, at the real libc; the same file already resolves malloc() and free() that way. larsonN-sized still fails, for a reason unrelated to the lookup.