Macros

The headerless.h file defines several macros that allow .c sources to be included directly, removing the need for accompanying header files.

H

The H macro (header) affects most other macros in headerless.h. H enables "header mode" when defined, causing most other macros to expand more conservatively. This should be defined before #include-ing a "headerless" .c file.

#define H
#include "file1.c"
#include "file2.c"

B

The B macro (body) is used to define function bodies in headerless .c files.

unsigned factorial(unsigned i)B(
	unsigned n = 1;
	while(i) n *= i--;
	return n;
)

C

The C macro (extern"C") can be used to specify C linkage, in case a headerless .c file is included by a C++ file.

C double sq(double x)B(
	return x*x;
)

E

The E macro (equals) is used to initialize non-static variables in headerless .c files.

int value E(0)

S

The S macro (static) is used to define static functions and variables in headerless .c files.

S(int value=0;)
S(double sq(double x))B(
	return x*x;
)

Usage

Including a headerless .c file in a normal file is fairly straightforward, as shown in the H macro example. However, complications arise when a headerless file tries to include other headerless files. For instance, assume we want to create our own headerless file.c which includes other headerless .c files, file1.c and file2.c:

#define H // WRONG - Now we can't use H to detect whether this file is being compiled or included!
#include "file1.c"
#include "file2.c"
#include "headerless.h"
//code...

A potential way to resolve this might be:

#ifdef H
#include "file1.c"
#include "file2.c"
#else
#define H
#include "file1.c"
#include "file2.c"
#undef H
#endif
#include "headerless.h"
//code...

However, this is quite verbose and requires listing all our .c includes twice. To prevent the duplication, we can do this:

#ifdef FILE_C
#include "file1.c"
#include "file2.c"
#else
#define FILE_C

#ifdef H
#include __FILE__
#else
#define H
#include __FILE__
#undef H
#endif

#include "headerless.h"
//code...
#endif

But this is still quite verbose! Fortunately, "headerless.h" allows F to be defined as the name of a file; if it is, the header will perform this inclusion for us:

#ifdef FILE_C
#include "file1.c"
#include "file2.c"
#else
#define FILE_C

#define F "file.c"
#include "headerless.h"
//code...
#endif

Finally, to deal with multiple or recursive inclusion, we still need an include guard:

#if FILE_C
#undef FILE_C
#define FILE_C
#include "file1.c"
#include "file2.c"
#elif !defined(FILE_C)
#define FILE_C 1

#define F "file.c"
#include "headerless.h"
//code...
#endif

Putting everything together gives us the working example above, allowing removal of header files at the cost of a minimal amount of boilerplate.