howToAccessLabel
:: DynFlags -> Arch -> OS -> ReferenceKind -> CLabel -> LabelAccessStyle
+
-- Windows
---
--- We need to use access *exactly* those things that
--- are imported from a DLL via an __imp_* label.
--- There are no stubs for imported code.
+-- In Windows speak, a "module" is a set of objects linked into the
+-- same Portable Exectuable (PE) file. (both .exe and .dll files are PEs).
+--
+-- If we're compiling a multi-module program then symbols from other modules
+-- are accessed by a symbol pointer named __imp_SYMBOL. At runtime we have the
+-- following.
+--
+-- (in the local module)
+-- __imp_SYMBOL: addr of SYMBOL
+--
+-- (in the other module)
+-- SYMBOL: the real function / data.
+--
+-- To access the function at SYMBOL from our local module, we just need to
+-- dereference the local __imp_SYMBOL.
+--
+-- If opt_Static is set then we assume that all our code will be linked
+-- into the same .exe file. In this case we always access symbols directly,
+-- and never use __imp_SYMBOL.
--
howToAccessLabel dflags _ OSMinGW32 _ lbl
+
+ -- Assume all symbols will be in the same PE, so just access them directly.
+ | opt_Static
+ = AccessDirectly
+
+ -- If the target symbol is in another PE we need to access it via the
+ -- appropriate __imp_SYMBOL pointer.
| labelDynamic (thisPackage dflags) lbl
= AccessViaSymbolPtr
+ -- Target symbol is in the same PE as the caller, so just access it directly.
| otherwise
= AccessDirectly