Auto merge of #37982 - rkruppe:llvm-diagnostic-fwdcompat, r=alexcrichton

[LLVM 4.0] OptimizationDiagnostic FFI forward compatibility

- getMsg() changed to return std::string by-value. Fix: copy the data to a rust String during unpacking.
- getPassName() changed to return StringRef

cc #37609

Author: bors

src/librustc_llvm/diagnostic.rs

@@ -48,29 +48,32 @@ pub struct OptimizationDiagnostic {
     pub pass_name: *const c_char,
     pub function: ValueRef,
     pub debug_loc: DebugLocRef,
-    pub message: TwineRef,
+    pub message: String,
 }
 
 impl OptimizationDiagnostic {
     unsafe fn unpack(kind: OptimizationDiagnosticKind,
                      di: DiagnosticInfoRef)
                      -> OptimizationDiagnostic {
-
-        let mut opt = OptimizationDiagnostic {
+        let mut pass_name = ptr::null();
+        let mut function = ptr::null_mut();
+        let mut debug_loc = ptr::null_mut();
+
+        let message = super::build_string(|message|
+            super::LLVMRustUnpackOptimizationDiagnostic(di,
+                                                        &mut pass_name,
+                                                        &mut function,
+                                                        &mut debug_loc,
+                                                        message)
+        );
+
+        OptimizationDiagnostic {
             kind: kind,
-            pass_name: ptr::null(),
-            function: ptr::null_mut(),
-            debug_loc: ptr::null_mut(),
-            message: ptr::null_mut(),
-        };
-
-        super::LLVMRustUnpackOptimizationDiagnostic(di,
-                                                    &mut opt.pass_name,
-                                                    &mut opt.function,
-                                                    &mut opt.debug_loc,
-                                                    &mut opt.message);
-
-        opt
+            pass_name: pass_name,
+            function: function,
+            debug_loc: debug_loc,
+            message: message.expect("got a non-UTF8 OptimizationDiagnostic message from LLVM")
+        }
     }
 }
 

src/librustc_llvm/ffi.rs

@@ -1823,7 +1823,7 @@ extern "C" {
                                                 pass_name_out: *mut *const c_char,
                                                 function_out: *mut ValueRef,
                                                 debugloc_out: *mut DebugLocRef,
-                                                message_out: *mut TwineRef);
+                                                message_out: RustStringRef);
     pub fn LLVMRustUnpackInlineAsmDiagnostic(DI: DiagnosticInfoRef,
                                              cookie_out: *mut c_uint,
                                              message_out: *mut TwineRef,

src/librustc_trans/back/write.rs

@@ -417,7 +417,7 @@ unsafe extern "C" fn diagnostic_handler(info: DiagnosticInfoRef, user: *mut c_vo
                                                 opt.kind.describe(),
                                                 pass_name,
                                                 if loc.is_empty() { "[unknown]" } else { &*loc },
-                                                llvm::twine_to_string(opt.message)));
+                                                opt.message));
             }
         }
 

src/rustllvm/RustWrapper.cpp

@@ -871,16 +871,21 @@ LLVMRustUnpackOptimizationDiagnostic(
     const char **pass_name_out,
     LLVMValueRef *function_out,
     LLVMDebugLocRef *debugloc_out,
-    LLVMTwineRef *message_out)
+    RustStringRef message_out)
 {
     // Undefined to call this not on an optimization diagnostic!
     llvm::DiagnosticInfoOptimizationBase *opt
         = static_cast<llvm::DiagnosticInfoOptimizationBase*>(unwrap(di));
 
+#if LLVM_VERSION_GE(4, 0)
+    *pass_name_out = opt->getPassName().data();
+#else
     *pass_name_out = opt->getPassName();
+#endif
     *function_out = wrap(&opt->getFunction());
     *debugloc_out = wrap(&opt->getDebugLoc());
-    *message_out = wrap(&opt->getMsg());
+    raw_rust_string_ostream os(message_out);
+    os << opt->getMsg();
 }
 
 extern "C" void