Comment author: @damiendoligez

Instead of providing a C include file, which would only work for future versions of OCaml, I wrote a shell script that produces such an include file from the version number provided by ocamlc. I suggest that you include a copy of that script with your sources and use it in your Makefile.

I have uploaded it here, and added it to the tools/ directory.

Sample output:

for 4.00.0+beta2:
#define OCAML_VERSION_MAJOR 4
#define OCAML_VERSION_MINOR 00
#define OCAML_VERSION_PATCHLEVEL 0
#define OCAML_VERSION_ADDITIONAL "beta2"

for 3.12.1:
#define OCAML_VERSION_MAJOR 3
#define OCAML_VERSION_MINOR 12
#define OCAML_VERSION_PATCHLEVEL 1
#undef OCAML_VERSION_SUFFIX

for 3.07:
#define OCAML_VERSION_MAJOR 3
#define OCAML_VERSION_MINOR 07
#define OCAML_VERSION_PATCHLEVEL 0
#undef OCAML_VERSION_ADDITIONAL

Comment author: @ygrek

Adding a C include file would still be useful..

Comment author: @oandrieu

« (one more field in the custom_operations struct) »

Actually this field was introduced in 3.12.1

Comment author: didc

My bad, I had ver. 3.11 and tried ver. 4 and assumed it was new. If it's the only thing that changed since then, it's probably not so much of a hurdle.
Generating the include file could be enough. This can be handled with regular Makefiles, OCamlMakefile (I tested this), and probably OMake too. For ocamlbuild, a solution maybe is writing the include script generator in ocaml and have it included somehow in myocamlbuild.ml.
Indeed, there's isn't a simple way to test from within the C stubs if a file effectively exists, so one would have to resort to using a test in the build scripts to check if the version include file exists or not, thus the solution offered seems better.
Thank you!