nx_dwarf_loclists.nx

nx_dwarf_loclists.nx -- DWARF v5 .debug_loclists builder. Companion to nx_dwarf_loc (single location expression at a fixed PC). loclists describes a variable's location as a SEQUENCE of (PC range, location expression) pairs -- needed when an optimizer moves the variable across registers / spills it to the frame at different points in the function. Without loclists, gdb shows the variable's last-known location at every breakpoint, which is wrong inside the optimized function body. With loclists, gdb shows '<optimized out>' outside any covered range and the right register/offset inside. Per-CU layout (DWARF v5 7.7.3) -- mirrors nx_dwarf_rnglists: length u32 version u16 = 5 addr_size u8 = 8 segment_selector u8 = 0 offset_entry_count u32 offsets[count] u32 loc lists sequence of DW_LLE_* opcodes DW_LLE_* opcodes (subset we emit): end_of_list 0x00 base_addressx 0x01 startx_endx 0x02 startx_length 0x03 offset_pair 0x04 default_location 0x05 base_address 0x06 start_end 0x07 start_length 0x08 Each entry that includes a "location description" is followed by a uleb128 length and that many bytes of DW_OP_* expression (built via nx_dwarf_loc). Pairs with nx_dwarf_loc (location-expression bytes) + nx_dwarf_info (DIE attributes referencing loclists offsets) + nx_dwarf_rnglists (sister section).