Symtab

Symtab, short for symbol table, is a data structure used by compilers, assemblers, linkers, and debuggers to record information about program symbols—identifiers that denote variables, functions, labels, and other entities. The symbol table supports name resolution, scope and linkage information, and, in object files, the relocation process. In many object file formats the symbol table is a dedicated section that lists entries for each symbol with fields such as name, value, size, info, other, and section index. For example, in the ELF format an entry includes st_name (offset into a string table), st_value (address or value), st_size, st_info (binding and type), st_other (visibility), and st_shndx (section index). A separate dynamic symbol table (.dynsym) exists for symbols needed at runtime by dynamic linkers.

During the build, the compiler emits symbol table entries, and the linker uses them to resolve references across translation units and libraries. Debuggers read symbol tables to map program addresses back to human-readable names and source locations. The symbol table can also facilitate profiling, exception handling, and relocation, as the linker may relocate addresses and adjust references based on symbol definitions.

Many production binaries are stripped of symbol tables to reduce size and protect intellectual property, in which case only dynamic symbols (if any) or no symbol information remains. Tools such as readelf, objdump, or nm can display symbol table contents when present.

Symtab is therefore central to the transition from human-readable source code to executable binaries, providing the metadata that enables linking, debugging, and analysis.