return_value. This function determines the return convention for a given data type. For example on the OpenRISC 1000, structs/unions and large (>32 bit) scalars are returned as references, while small scalars are returned in GPR 11. This function should always be defined.

breakpoint_from_pc. Returns the breakpoint instruction to be used when the PC is at a particular location in memory. For architectures with variable length instructions, the choice of breakpoint instruction may depend on the length of the instruction at the program counter. Returns the instruction sequence and its length.

The default value is NULL (undefined). This function should always be defined if GDB is to support breakpointing for this architecture.

adjust_breakpoint_address. Some architectures do not allow breakpoints to be placed at all points. Given a program counter, this function returns an address where a breakpoint can be placed. Default value is NULL (undefined). The function need only be defined for architectures which cannot accept a breakpoint at all program counter locations.

memory_insert_breakpoint and memory_remove_breakpoint. These functions insert or remove memory based (a.k.a. soft) breakpoints. The default values default_memory_insert_breakpoint and default_memory_remove_breakpoint are suitable for most architectures, so in most cases these functions need not be defined.

decr_pc_after_break. Some architectures require the program counter to be decremented after a break, to allow the broken instruction to be executed on resumption. This function returns the number of bytes by which to decrement the address. The default value is NULL (undefined) which means the program counter is left unchanged. This function need only be defined if the functionality is required.

In practice this function is only of use for the very simplest architectures. It applies only to software breakpoints, not watchpoints or hardware breakpoints. It is more usual to adjust the program counter as required in the target to_wait and to_resume functions (see Section 2.4).

single_step_through_delay. Returns 1 if the target is executing a delay slot and a further single step is needed before the instruction finishes. The default value is NULL (not defined). This function should be implemented if the target has delay slots.

print_insn. Disassemble an instruction and print it. Default value is NULL (undefined). This function should be defined if disassembly of code is to be supported.

Disassembly is a function required by the binutils library. This function is defined in the opcodes sub-directory. A suitable implementation may already exist if binutils has already been ported.