C Constants
1 Introduction
2 Usage

C Constants

1 Introduction

This is a simple package for fetching #define’d values from C files. It simply creates a temporary file with the appropriate #includes, throws a printf call into main, compiles and runs. The only dependency as of now is a working C compiler.

2 Usage

Usage of this package revolves around one function:


(c-defs header ... [#:compiler compiler])

  ((string?) #:rest (listof string?) . ->* . (values any/c ...))
  header : string?
  compiler : (or/c path? #f) = #f
Creates a function which can be used to access C constants.

The header inputs are a sequence of strings which will be wrapped in #include statements at the top of the C file (note that these statements will be in the same order as the provided header ... sequence), in the same way that one would write them in C (e.g. "escheme.h")

The optional compiler argument is a path to the C compiler to use when creating the temporary file. If omitted, the package will attempt to locate a C compiler on the system’s PATH.

The resulting function takes a series of strings as input.

The first string corresponds to a C printf format string which will be used to print all constants in the current function call. The remaining strings are the names of the constants to resolve.

The return value of this function is a "values" expression which contains the values of the desired constants. The formatting string is parsed by the package, so the return values are of the appropriate type as well.

> (require c-defs)
> (define PYTHON-CONSTANTS (c-defs "python3.4/Python.h"
> (define-values (T-SHORT T-OBJ)
                      "T_SHORT" "T_OBJECT"))

No C compiler found.

Please install clang or gcc


T-OBJ: undefined;

 cannot reference an identifier before its definition

  in module: 'program