debug information
Extra data the compiler writes when you build with -g, so a debugger can show your source lines, function names and variables instead of bare addresses.
Debug information (DWARF on Linux and macOS, CodeView/PDB on Windows) maps machine-code addresses to source lines, describes types, and gives each variable's location (a stack slot, a register, or a range-dependent list of locations); it is emitted with -g or /Zi and does not change the generated code.
See also