84 lines
2.1 KiB
Markdown
84 lines
2.1 KiB
Markdown
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+++
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title = "linking"
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draft = false
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tags = [
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"code",
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"c",
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"linking"
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]
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date = "2014-03-26"
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+++
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# Linking obj/dlls
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Probleemstelling: verschillende **solutions**, code over solutions heen willen gebruiken.
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Dit compileert by default altijd, maar tijdens het linken van de gecompileerde files loopt het mis. Waarom? Omdat er geen `dllexport` voorzien is.
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<br/><br/> Op te lossen:
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```c
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#ifndef RESOURCE_UTILS_H
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#define RESOURCE_UTILS_H
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#include "Utility.h"
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#ifdef _DLL
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#define DllExImport __declspec(dllexport)
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#else
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#define DllExImport __declspec(dllimport)
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#endif
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class DllExImport ResourceUtils
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{
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public:
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static RAIIObject<HICON> getIcon(int resourceId);
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static RAIIObject<HICON> getIcon(HINSTANCE resourceHandleInstance, int resourceId);
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private:
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ResourceUtils() {}
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};
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#endif
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```
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in de cpp file hoeft niets speciaal meer te staan.
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#### Functies exposen voor native calls
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Zelfde principe om klassen te exposen met `_ _declspec(dllexport)`. Gebruik eventueel std calls (C# heeft dit nodig): `DllExImport MyStruct* _ _stdcall GetSignals();`.
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#### Properties van solutions
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##### Die de te exporteren code bevat
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1. Configuration type: Dynamic Libraray (DLL)
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2. Incremental linking: Yes (/INCREMENTAL)
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3. Link Linkage Deps: Yes
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4. Output file: *.dll
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##### Die de code bevat die gebruik maakt van de dll
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1. Linker; Input: Additional dependencies ../OtherSolution.lib
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### Shared libraries linken in Unix
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`declspec` is Win32 specifiek. Lees alles over GCC Visibility in [GNU GCC Wiki on Visibility](http://gcc.gnu.org/wiki/Visibility). Komt op dit neer:
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```c
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#if defined(_MSC_VER)
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// Microsoft
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#define EXPORT __declspec(dllexport)
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#define IMPORT __declspec(dllimport)
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#elif defined(_GCC)
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// GCC
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#define EXPORT __attribute__((visibility("default")))
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#define IMPORT
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#else
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// do nothing and hope for the best?
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#define EXPORT
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#define IMPORT
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#pragma warning Unknown dynamic link import/export semantics.
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#endif
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```
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Zie ook [How to write shared Libraries](http://www.akkadia.org/drepper/dsohowto.pdf) by Ulrich Drepper.
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