Summary: Dl_info struct should only be used if dladdr() has returned non-zero (no errors) and always check the dladdr() return value; Dl_info.dli_sname and Dl_info.dli_saddr fields should only be used if non-NULL; update/improve runtime/6888954/vmerrors.sh test
Reviewed-by: dsamersoff, zgu, hseigel, coleenp