$ Linux Command

Development

protoize

Add ANSI C prototypes to legacy C source code.

cprototypingansiconversionlegacy code

Additional Notes

protoize is a tool from the GNU Compiler Collection (GCC) that automatically adds ANSI C function prototypes to legacy K&R-style C source files. It reads C source code written in pre-ANSI style (with old-style function definitions) and generates new source files with proper ANSI/ISO C prototypes and modern function declarations.

The companion tool unprotoize reverts the process, converting ANSI prototypes back to K&R style. Both tools are rarely needed today since most C code follows ANSI standards, but they remain useful for maintaining or modernizing very old codebases.

Syntax

protoize [options] [file...]
unprotoize [options] [file...]

Parameters

  • options: Flags that change how protoize behaves.
  • target: Optional file, device, interface, user, service, or command target when the command supports one.

Common Options

  • -c, --compile: Run the compiler on the modified files after conversion.
  • -d, --delete: Delete the original unmodified files after conversion.
  • -k, --keep: Keep copies of original files with .save extension.
  • -l, --local: Convert local functions as well as external ones.
  • -n, --no-backup: Do not create backup files.
  • -p, --prompt: Prompt before modifying each file.
  • -q, --quiet: Reduce output verbosity.
  • -v, --verbose: Show detailed processing information.
  • -x, --exclude: Exclude specified files from conversion.
  • --help: Show help and exit.
  • --version: Show version information.
  • -B directory: Specify a directory for backup files.
  • -I directory: Add to the include file search path.
  • -D name: Predefine a macro.
  • -U name: Undefine a macro.

Examples

protoize *.c

Add ANSI prototypes to all C source files in the current directory.

protoize -k -v main.c utils.c

Convert specified files, keeping .save backups, with verbose output.

protoize -c -q src/*.c

Convert and then compile-check the modified source files.

unprotoize *.c

Revert ANSI prototypes back to K&R style.

protoize -p *.c

Prompt before modifying each file.

Practical Notes

  • protoize makes extensive modifications to source files. Always back up your code before running it.
  • The tool requires correct preprocessing; macros and #include directives must resolve correctly for proper conversion.
  • protoize may fail or produce incorrect results with very complex preprocessor usage or non-standard compiler extensions.
  • Modern C code does not need protoize. It is intended for migrating code written before the ANSI C standard (C89/C90).
  • The unprotoize tool can generate K&R-style code that may be compilable with very old C compilers.
  • These tools are part of GCC but may not be installed by default on modern systems. Install them with the gcc or gcc-<version> package.