Correctly import foreign statics

Previously foreign statics would actually cause a local static to be
defined and exported. This issue was found because std::env::vars() was
found to return no env vars despite many being defined. This was caused
by libstd importing environ as foreign static. The accidental definition
of environ caused libstd to read a null pointer which was interpreted as
there being no environment variables at all.

Author: bjorn3

src/consts.rs

@@ -218,7 +218,7 @@ impl<'gcc, 'tcx> CodegenCx<'gcc, 'tcx> {
                         }
 
                         let is_tls = fn_attrs.flags.contains(CodegenFnAttrFlags::THREAD_LOCAL);
-                        let global = self.declare_global(&sym, llty, is_tls, fn_attrs.link_section);
+                        let global = self.declare_global(&sym, llty, false, is_tls, fn_attrs.link_section);
 
                         if !self.tcx.is_reachable_non_generic(def_id) {
                             // TODO(antoyo): set visibility.
@@ -389,6 +389,6 @@ fn check_and_apply_linkage<'gcc, 'tcx>(cx: &CodegenCx<'gcc, 'tcx>, attrs: &Codeg
         // don't do this then linker errors can be generated where the linker
         // complains that one object files has a thread local version of the
         // symbol and another one doesn't.
-        cx.declare_global(&sym, llty, is_tls, attrs.link_section)
+        cx.declare_global(&sym, llty, true, is_tls, attrs.link_section)
     }
 }

src/declare.rs

@@ -22,7 +22,7 @@ impl<'gcc, 'tcx> CodegenCx<'gcc, 'tcx> {
             global
         }
         else {
-            self.declare_global(name, ty, is_tls, link_section)
+            self.declare_global(name, ty, false, is_tls, link_section)
         }
     }
 
@@ -47,8 +47,8 @@ impl<'gcc, 'tcx> CodegenCx<'gcc, 'tcx> {
         unsafe { std::mem::transmute(func) }
     }*/
 
-    pub fn declare_global(&self, name: &str, ty: Type<'gcc>, is_tls: bool, link_section: Option<Symbol>) -> LValue<'gcc> {
-        let global = self.context.new_global(None, GlobalKind::Exported, ty, name);
+    pub fn declare_global(&self, name: &str, ty: Type<'gcc>, is_import: bool, is_tls: bool, link_section: Option<Symbol>) -> LValue<'gcc> {
+        let global = self.context.new_global(None, if is_import { GlobalKind::Imported } else { GlobalKind::Exported }, ty, name);
         if is_tls {
             global.set_tls_model(self.tls_model);
         }