December 01, 2018 Template matches more than one template declaration error when trying to pass function's pointer | ||||
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After some refactoring, there are four functions sharing the same name (technically four, but LDC didn't complain about them): @nogc void blitter(T)(T* src, T* dest, size_t length){...} and @nogc void blitter(T)(T* src, T* dest, size_t length, T* mask){...} I need the first one, but at compilation time I get the following error: pixelperfectengine\src\PixelPerfectEngine\graphics\layers.d(61,30): Error: template CPUblit.composing.blitter matches more than one template declaration: ..\..\..\AppData\Local\dub\packages\cpublit-0.2.3\cpublit\src\CPUblit\composing.d(2006,19): blitter(T)(T* src, T* dest, size_t length) and ..\..\..\AppData\Local\dub\packages\cpublit-0.2.3\cpublit\src\CPUblit\composing.d(2274,19): blitter(T)(T* src, T* dest, size_t length, T* mask) |
November 30, 2018 Re: Template matches more than one template declaration error when trying to pass function's pointer | ||||
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Posted in reply to solidstate1991 | On Sat, Dec 01, 2018 at 01:17:55AM +0000, solidstate1991 via Digitalmars-d-learn wrote: > After some refactoring, there are four functions sharing the same name (technically four, but LDC didn't complain about them): > > @nogc void blitter(T)(T* src, T* dest, size_t length){...} > > and > > @nogc void blitter(T)(T* src, T* dest, size_t length, T* mask){...} > > I need the first one, but at compilation time I get the following error: > > pixelperfectengine\src\PixelPerfectEngine\graphics\layers.d(61,30): Error: template CPUblit.composing.blitter matches more than one template declaration: > ..\..\..\AppData\Local\dub\packages\cpublit-0.2.3\cpublit\src\CPUblit\composing.d(2006,19): blitter(T)(T* src, T* dest, size_t length) > and > ..\..\..\AppData\Local\dub\packages\cpublit-0.2.3\cpublit\src\CPUblit\composing.d(2274,19): blitter(T)(T* src, T* dest, size_t length, T* mask) For non-template overloaded functions, you can get the address by casting the function pointer, e.g.: void fun(int size) { writeln("1"); } void fun(int size, float z) { writeln("2"); } auto p1 = cast(void function(int)) &fun; auto p2 = cast(void function(int, float)) &fun; auto p3 = cast(void function(int, string)) &fun; p1(0); // prints "1" p2(0, 0f); // prints "2" p3(0, ""); // prints "1" (!) It's sorta weird when the cast doesn't match any overload; the compiler seems to just arbitrarily select the first one. However, for template functions, casting isn't enough; you need __traits(getOverloads): alias ovs = __traits(getOverloads, myModule, "gun", true); foreach (ov; ovs) { writeln(ov.stringof); } prints: gun(T)(T t, int size) gun(T)(T t, int size, float z) But actually coaxing the address out of the function is rather ugly: // These don't work: //auto q = &ovs[0]!int; //auto q = &(ovs[0]!int); //auto q = &(ovs[0])!int; // ... etc. // But this does: alias ov1 = ovs[1]; auto q = &ov1!int; q(0, 1, 1f); // prints "4" However, there appears to be a bug: if you try to access the first overload, it doesn't work again! // But this does: alias ov0 = ovs[0]; // NG: compile error! auto q = &ov0!int; q(0, 1, 1f); Sounds like a compiler bug should be filed. :-/ I tried to hack it by using AliasSeq to insert a dummy first element to the sequence then using [1] to access the first overload, but got the same error. I guess internally somehow the compiler isn't treating the first overload case correctly, independently of its position in the tuple / AliasSeq. T -- Nearly all men can stand adversity, but if you want to test a man's character, give him power. -- Abraham Lincoln |
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