Programmatically create header file

Question

What's the best way to programmatically create a header file for another project?

Here's the specific use case: one program fingerprints the device for discrete information like version number, id string, etc, and then creates a header file populating static structs/program constants. This header file is then consumed by multiple projects to define a type of that class.

I thought about reading writing in an xml or flat file, that means consuming projects need to know that structure of the and plug in libraries to read it.

• Mahmoud Hossam: I think this is better suited for SO.
• user8: This question is fine here: Programmmers.SE is about write-boarding ideas. There's nothing about this question that involves getting into code.
• Martin Wickman: These things can be done with a macro language like m4 which is very well suited to generate files from templates.

Answer 1

If you're building on *NIX (Unix, Linux, or OSX), a common approach is to have a make rule that converts a .h.in to .h using sed (or perl). The implementation would vary on Windows, but what you should be aiming at is

project.h.in:

#define VERSION __VERSION__
#define COPYRIGHT __COPYRIGHT__
#define SOMETHING_ELSE __SOMETHING_ELSE__

Your fingerprinting tool (or a wrapper around it) then does simple text replacement, so you end up with

#define VERSION 2.3.4
#define COPYRIGHT "(C) 2011 Stack Overflow"
#define SOMETHING_ELSE "A bucket of fish"

You could use Ant to do replacements (although Ant isn't really the right tool for C programming)

Depending on what exactly you're fingerprinting, automake/autoconf might be worth investigating - on Windows you may need to run these under MinGW or cygwin.

Using a template like this means you can leave any header comments, macro definitions, etc. in the header template.

• S.Lott: They often use m4 for this. It has a learning curve, but works out well in the long run. en.wikipedia.org/wiki/M4_(computer_language)
• alternative: m4 is usually used to generate code that then uses sed to create the macros, actually.
• Sorcerer13: Thanks, that's something like I was angling towards. The project is to poll a usb device, and produce a set of pre-populated #defs and structs which describe the device (e.g. hw id, transfer rate, etc) in a single file. You can then include that file in any number of projects, e.g. in Teensy usb programming projects.

Answer 2

Your build automation infrastructure would deal with included headers. Consider using GNU make (or ninja, etc...). If your C compiler is GCC (or Clang), notice the -M and related compiler flags. You might also want to use ccache and/or precompiled headers to speed up incremental build time. But read Recursive make considered harmful and consider other build automation tools, perhaps even omake or scons.

Your Makefile could contain -include directives. With ninja, your build.ninja file is usually generated (e.g. by some ad-hoc Python or Guile script, by cmake or meson, etc...), etc...

Both Bismon and RefPerSys are generating more and more of their own header files (in Bismon: C files; in RefPerSys: C++ files). But so do s48, CAIA (see this, old tarball here), and Chicken/Scheme.