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Fix template substitution with const #677

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merged 5 commits into from
May 16, 2023

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HGuillemet
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template <typename T>
class X {
 public:
    X(const T*) {}
};

If you instantiate this template with int *, then the resulting type should be int * const * and not const int **.
But the parser produces this, with a new Info("X<int *>").pointerTypes("XI"):

    public XI(@Cast("const int**") PointerPointer arg0) { super((Pointer)null); allocate(arg0); }
    private native void allocate(@Cast("const int**") PointerPointer arg0);

Leading to JNI compile error since the constructor expects a int * const*.
This PR tries to fix this. It seems to do the trick. The parser now emits:

    public XI(@Cast("int**") PointerPointer arg0) { super((Pointer)null); allocate(arg0); }
    private native void allocate(@Cast("int**") PointerPointer arg0);

The const doesn't appear in the cast at all, but at least we have a better chance to compile the JNI.
I'm not sure it generalizes well. Can we do something better ?

@saudet
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saudet commented May 14, 2023

Info.constPointer currently gets ignored in this case, yes. It's complicated, but if this fix works for that template that's fine for now. We can do something about Info.constPointer later, I think that's OK, yes. Did you make sure it doesn't break anything in the presets though?

@HGuillemet
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Just finished to reparse (almost) all presets. Only changes are for pytorch where const is removed from @Cast in the following declarations:

In BlockArrayRef.java:

public native @Cast("torch::jit::Block**") PointerPointer data();

In ValueArrayRef.java

public native @Cast("torch::jit::Value**") PointerPointer data();

JNI still compiles.

@saudet saudet merged commit 78b9450 into bytedeco:master May 16, 2023
@HGuillemet HGuillemet deleted the fix_const_template branch May 16, 2023 12:58
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2 participants