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diff --git a/compiler/DLL-NOTES b/compiler/DLL-NOTES new file mode 100644 index 0000000000..c710b14251 --- /dev/null +++ b/compiler/DLL-NOTES @@ -0,0 +1,58 @@ + The DLL story + ------------- + +*** + +This file is intended to be a focal point for notes on how DLLs work. Please +add cross-references to source and other docs, especially when you don't +find something here that you need. + +*** + + +Introduction +------------ + +On Windows, DLLs are synonymous with packages (since 4.07; this change +simplified a rather horrible mess). Hence whenever a module is to be +compiled to go in a DLL, it must be compiled with -package-name dll-name. +Typically, failing to do this gives Windows error message boxes of the form +"The instruction at address <x> tried to read memory at address <x>". + + +Dependencies +------------ + +Because references in DLLs must be fully resolved when the DLL is compiled +(except for references to other DLLs), it is not possible for DLLs to call +the main program. This means that the parts of the RTS and standard package +which call the main program cannot be compiled into the relevant DLLs, and +must instead be compiled as standalone object files and linked in to each +executable. This gives the following picture of dependencies within a program: + + ___________ ___________ + | |------>| | GHC-land | Application-land +DLL-land | HSrts.dll | | HSstd.dll | | + |___________|<------|___________| | + | ^ | +-----------------|-------------------|-------------------| + _____v_____ _____|______ | +.o-land | | | | | + | Main.o | | PrelMain.o |----------------------- + |___________| |____________| | | + | | ______v______ + | | | | + ------------------------------------------>| Main.o | + | |_____________| + +(The application's dependencies are not shown.) + + +Bits of the compiler that deal with DLLs +---------------------------------------- + +basicTypes/Module.lhs is the most important place, as it deals with which +modules identifiers are in. + +basicTypes/name.lhs, other bits of basicTypes/, nativeGen/, codeGen/, +abcCSyn/, and even profiling/ have other references. |