In Release modes, Visual Studio complains that the Operator destructor in User.cpp

never returns, which is true by design.

Initially assumed that the reason is llvm_unreachable being dependent on NDEBUG.

However, even if llvm_unreachable is replaced by __assume(false), VC still warns in
Release modes but not in Debug modes...

The real reason turned out to be optimization flags.
With /Od in Debug modes the warning is not issued whereas with /O1 it is.

I could not find any documentation to this effect, but it is reproducable:

Try compiling http://msdn.microsoft.com/en-us/library/khwfyc5d(v=vs.90).aspx
with /O1 and then with /Od.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@204659 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/IR/User.cpp b/lib/IR/User.cpp
index 940682826acc2a799577f0a3d35734875071f168..cd124df1e93359e1da5b3b1744450447909a0854 100644 (file)
--- a/lib/IR/User.cpp
+++ b/lib/IR/User.cpp
@@ -83,8 +83,28 @@ void User::operator delete(void *Usr) {
 //                             Operator Class
 //===----------------------------------------------------------------------===//
 
+#if defined(_MSC_VER)\r
+// In Release modes, Visual Studio complains that the Operator destructor\r
+// never returns, which is true by design. \r
+// This does *not* depend on llvm_unreachable being dependent on NDEBUG:\r
+// even if llvm_unreachable is replaced by __assume(false), VC still warns in\r
+// Release modes but not in Debug modes. The real reason is optimization flags.\r
+// With /Od in Debug modes the warning is not issued whereas with /O1 it is.\r
+// I could not find any documentation to this effect, it is reproducable:\r
+// Try compiling http://msdn.microsoft.com/en-us/library/khwfyc5d(v=vs.90).aspx\r
+// with /O1 and then with /Od.\r
+// Anyhow, solution is same as lib/Support/Process.cpp:~self_process().\r
+\r
+#pragma warning(push)\r
+#pragma warning(disable:4722)\r
+#endif\r
+\r
 Operator::~Operator() {
   llvm_unreachable("should never destroy an Operator");
 }
 
+#if defined(_MSC_VER)\r
+#pragma warning(pop)\r
+#endif\r
+
 } // End llvm namespace