Automatically create Delphi/Freepascal interface unit from C header file

Question

Is it possible to automatically generate interface units from C header files? In particular, I want to wrap the HDF5 library, and it would be great if I could avoid writing the interface unit manually.

That looks like a very large and complex library. I will confidently predict that there is no tool that does a good and comprehensive translation. — David Heffernan, Oct 17 '12 at 17:56
There is a partial translation to Delphi of version 4 of the hdf library [here](http://dspatial.sourceforge.net/). You will find it under the `Drivers` folder. It may serve as a first step of translation. — LU RD, Oct 17 '12 at 18:10
Problem is HDF4 and HDF5 don't share anything except for the *HDF* in their name ... — andreas-h, Oct 17 '12 at 20:42

score 12 · Accepted Answer · answered Oct 17 '12 at 16:48

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The free pascal includes the H2PAS tool.

h2pas attempts to convert a C header file to a pascal unit. it can handle most C constructs that one finds in a C header file, and attempts to translate them to their pascal counterparts.

answered Oct 17 '12 at 16:48

RRUZ

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It is way better than other tools I used, but in practice you need to still do a lot of post processing by hand. – Jeroen Wiert Pluimers Oct 17 '12 at 18:54

Ken White · Answer 2 · 2012-10-17T17:17:27.020

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Bob Swart (Dr Bob) has a utility which will convert a lot of header files (although there's usually some manual work involved as well) called HeaderConvert. I've never compared it to the tool @RRUZ links, but it's another option.

Project JEDI has one as well; I've never tested it. You can find it here.

edited Oct 17 '12 at 17:17

answered Oct 17 '12 at 16:50

Ken White

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The Jedi one is basically the same as headconv. – Marco van de Voort Oct 19 '12 at 11:00

score 5 · Answer 3 · edited Oct 17 '12 at 21:18

In general fully automated translating of C headers to something else (that isn't an effective superset of the needed C functionality) is hard to impossible.

This because due to macros one can't see how to translate them. Macros often only get their meaning from context. Example

#define uglymacro 1,2,3,4

but also (and this one is more common):

SCARYAPIMACRO void func(int c);

SCARYAPIMACRO is then often a macro that tests OS defines to select the right calling convention for the right OS/architecture.

Still, that doesn't mean that the tools are not real timesavers. But the result is more semiautomatic, I've the most and best experience with h2pas.

I've translated a lot of Windows headers (including FPC's commctrl which has a sendmessage macro every few lines).

What I usually do is craft a small pascal program that scans the source linebased and uses heuristics to split it into parts that are mostly homogeneous (all structs or constants,macros, procedure declaration etc). Then I look at the source and often do some global substitutes.

Only then I run it through the translator, the process is often iterative (refine separation, do global substitutions, try to translate, if it fails, try again etc).

The process unfortunately does require a good grasp of C, pragma stuff included.

score 1 · Answer 4 · answered Nov 26 '12 at 13:27

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You can download HDF5 API header Delphi translations, Delphi XE2 HDF5 table test program with source code and somewhat modified hdf5dll from my page: http://www.astro.ff.vu.lt/index.php?option=com_content&task=view&id=46&Itemid=63

answered Nov 26 '12 at 13:27

SauliusR

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Automatically create Delphi/Freepascal interface unit from C header file

4 Answers4