cdecl

C and C++ type declaration translator

TLDR

Start interactive mode

$ cdecl

Explain a C declaration

$ cdecl explain "int *(*fp)(int)"

Convert English to a C declaration

$ cdecl declare "x as pointer to function returning int"

Explain a complex function declaration

$ cdecl explain "void (*signal(int, void (*)(int)))(int)"

Cast an expression

$ cdecl cast "x into pointer to function returning int"

Declare using English via pipe

$ echo "declare argv as array of pointer to char" | cdecl

Define a typedef

$ cdecl declare "str as typedef pointer to char"

cdecl (C declaration) translates complex C and C++ type declarations between their cryptic syntax and plain English. It helps programmers understand and construct complicated declarations involving pointers, arrays, and functions.The tool can explain existing declarations like function pointers, arrays of pointers, or pointers to arrays in understandable terms. Conversely, it can generate correct C syntax from English descriptions, helping avoid common declaration mistakes.In interactive mode, cdecl provides a prompt where you can enter multiple explain or declare commands. It handles complex scenarios like pointers to functions returning pointers to arrays, signal handler declarations, and other notoriously confusing C constructs.The C++ mode adds support for references and member pointers. The tool is particularly valuable when working with legacy code, signal handlers, callback functions, or any code with deeply nested type declarations.

PARAMETERS

Use C++ syntax instead of C (same as -c).

-c

Use C++ syntax instead of C.

-i

Enter interactive mode (default if no command given).

-V

Display version information.

explain declaration

Convert C/C++ declaration to English.

declare description

Convert English description to C/C++ declaration.

cast expression

Create a cast expression.

typedef declaration

Create a typedef from a declaration.

set option

Set options (e.g., cplusplus, preansi).

help

Display help in interactive mode.

quit

Exit interactive mode.

INSTALL

sudo apt install cdecl

sudo dnf install cdecl

sudo zypper install cdecl

brew install cdecl

nix profile install nixpkgs#cdecl

CAVEATS

Some very complex or non-standard declarations may not be parsed correctly. The tool focuses on type declarations and does not handle full C/C++ syntax. Newer C++ features (concepts, auto, etc.) may not be supported. Different versions may have slightly different English phrasing.

HISTORY

cdecl was originally written by Graham Ross and later enhanced by several contributors including David Wolverton. It emerged in the 1980s when C's declaration syntax was a frequent source of confusion and bugs. The phrase "declare x as..." became a teaching tool for understanding C's inside-out declaration reading. The tool remains useful today for complex declarations.