Add def.h to bindgen + solved deprecation warning
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… callback The new callback is needed because bindgen cannot infer type-casted macros. For example the macro '#define SCIP_INVALID (double)1e99' is too complicated. This is because of the type-cast to double. If we simply remove the (double), then bindgen CAN generate a binding for it. It also defaults to an `f64` in Rust, which is what the C-representation would look like too. The callback should only be used for types of which we know that Rust can infer the datatype. Therefore, I made sure that it only goes off on; 1. macros that the user deliberately targets (added via `target`-method) 2. only looks at casts to clang-keywords. So no weird custom mumbo-jumbo casts
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This is great! thanks a lot @HunkBenny. Just one thing as a sanity check, please add a test that just accesses something from def.h. Just to test that it works on all setup methods. |
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Do you think something as simple as this would work? |
mmghannam
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Dec 12, 2025
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Yes that was exactly what I had in mind. thank you! |
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Hi Mo!
Sorry in advance for also including a deprecation-warning fix in this PR, figured I would tackle that one as well.
The reason why I need this is because of
SCIP_INVALID. (See scipopt/russcip#269)This constant is defined as a C-macro over here; https://scipopt.org/doc/html/def_8h_source.php#l00178. It would be nice if we had access to this macro in Rust as well. By letting
bindgengenerate these constants, we do not need to manually define everything ourselves. Therefore, I added 'def.h' tobindgen.There was one problem though,
bindgenhas a hard time when dealing with type-casts in macros. Therefore it skipped generating bindings forSCIP_INVALID. The solution for this was defining a callback by implementing this trait. This callback looks for a pattern like: '( KEYWORD )', where I believe the KEYWORD to be a clang-keyword. I did not dare to dive further in the clang-rabbithole, but it seemed to work for standard C-types (double) and not for other types likeSCIP_Real. Which is precisely what I think we should want.As an extra safety I made sure that the macros we want to target should be added to the
DeriveCastedConstantstruct. I think thatbindgenmust have a good reason why it ignores type-casted macros, so I think it is best to not let this callback blindly noscope every single type-casted macro that crosses its path!I tested this in my local version of
russcipand was able to accessffi::SCIP_INVALID. 🎉