Merge pull request rust-lang#113 from TheDan64/dont_link_owned_module

Don't allow linking in owned module

Author: TheDan64

src/module.rs

@@ -1285,13 +1285,17 @@ impl Module {
     /// assert!(module.link_in_module(module2).is_ok());
     /// ```
     pub fn link_in_module(&self, other: Self) -> Result<(), LLVMString> {
-        // REVIEW: Check if owned by EE? test_linking_modules seems OK as is...
+        if other.owned_by_ee.borrow().is_some() {
+            let string = "Cannot link a module which is already owned by an ExecutionEngine.\0";
+            return Err(LLVMString::create(string));
+        }
 
         #[cfg(any(feature = "llvm3-6", feature = "llvm3-7"))]
         {
             use llvm_sys::linker::{LLVMLinkerMode, LLVMLinkModules};
 
             let mut err_string = ptr::null_mut();
+            // As of 3.7, LLVMLinkerDestroySource is the only option
             let mode = LLVMLinkerMode::LLVMLinkerDestroySource;
             let code = unsafe {
                 LLVMLinkModules(self.module.get(), other.module.get(), mode, &mut err_string)

tests/all/test_module.rs

@@ -415,17 +415,9 @@ fn test_linking_modules() {
 
     let execution_engine2 = module6.create_jit_execution_engine(OptimizationLevel::None).expect("Could not create Execution Engine");
 
-    // EE owned module links in EE owned module
-    assert!(module.link_in_module(module6).is_ok());
-
-    // EE2 still seems to "work" despite merging module6 into module...
-    // But f4 is now missing from EE2 (though this is expected, I'm really
-    // suprised it "just works" without segfault TBH)
-    // TODO: Test this much more thoroughly
-    #[cfg(feature = "llvm3-6")] // Likely a LLVM bug that 3-6 says ok, but others don't
+    // EE owned module cannot link another EE owned module
+    assert!(module.link_in_module(module6).is_err());
     assert_eq!(execution_engine2.get_function_value("f4"), Ok(fn_val4));
-    #[cfg(not(feature = "llvm3-6"))]
-    assert_ne!(execution_engine2.get_function_value("f4"), Ok(fn_val4));
 }
 
 #[test]