proper fix for windows

Author: timotheecour

compiler/ast.nim

@@ -856,6 +856,8 @@ type
     loc*: TLoc
     annex*: PLib              # additional fields (seldom used, so we use a
                               # reference to another object to save space)
+    cname*: string            # resolved C declaration name in importc decl, eg:
+                              # {.importc: "foo".} => cname = foo
     constraint*: PNode        # additional constraints like 'lit|result'; also
                               # misused for the codegenDecl pragma in the hope
                               # it won't cause problems

compiler/cgen.nim

@@ -697,14 +697,10 @@ proc loadDynamicLib(m: BModule, lib: PLib) =
 proc mangleDynLibProc(sym: PSym): Rope =
   # we have to build this as a single rope in order not to trip the
   # optimization in genInfixCall, see test tests/cpp/t8241.nim
-  when not defined(windows):
-    # mysterious bug that only affects windows, causing SIGSEGV in
+  if sym.loc.r != nil:
+    # `return rope($sym.loc.r)` would cause on windows a SIGSEGV in
     # stdlib_winleanDatInit000 () at generated_not_to_break_here
-    if sym.loc.r != nil:
-      if sym.loc.r.data.len > 0:
-        return sym.loc.r
-      else:
-        return rope($sym.loc.r)
+    if sym.cname.len == 0: sym.cname = $sym.loc.r
   if sfCompilerProc in sym.flags:
     # NOTE: sym.loc.r is the external name!
     result = rope(sym.name.s)

compiler/evalffi.nim

@@ -47,7 +47,8 @@ const
   nkPtrLit = nkIntLit # hopefully we can get rid of this hack soon
 
 proc importcSymbol*(conf: ConfigRef, sym: PSym): PNode =
-  let name = $sym.loc.r
+  var name = $sym.cname
+  if name.len == 0: name = $sym.loc.r
   # the AST does not support untyped pointers directly, so we use an nkIntLit
   # that contains the address instead:
   result = newNodeIT(nkPtrLit, sym.info, sym.typ)

compiler/vm.nim

@@ -281,7 +281,7 @@ proc putIntoReg(dest: var TFullReg; n: PNode) =
     if dest.kind == rkNode:
       dest.node = n
       return
-    elif n.typ.kind == tyPtr:
+    elif n.typ != nil and n.typ.kind == tyPtr:
       dest = TFullReg(kind: rkNode, node: n)
       return