MIPS ECOFF as supports several directives used for
generating debugging information which are not support by traditional MIPS
assemblers. These are .def, .endef, .dim, .file,
.scl, .size, .tag, .type, .val,
.stabd, .stabn, and .stabs. The debugging information
generated by the three .stab directives can only be read by GDB,
not by traditional MIPS debuggers (this enhancement is required to fully
support C++ debugging). These directives are primarily used by compilers, not
assembly language programmers!