From bf8f50f6eb28ec6a8806032d06a0412c75aca170 Mon Sep 17 00:00:00 2001
From: David Zarzycki <dave@znu.io>
Date: Tue, 16 Jun 2020 08:06:12 -0400
Subject: [PATCH] [Reflection] NFC: Workaround LLVM C++ standard library
 weirdness

Pull request #32244 introduced the use of `std::stringstream` but that
causes vtables to be generated and we don't want that.
---
 include/swift/Reflection/ReflectionContext.h | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/include/swift/Reflection/ReflectionContext.h b/include/swift/Reflection/ReflectionContext.h
index 82c39157df7e6..059149eaa26e2 100644
--- a/include/swift/Reflection/ReflectionContext.h
+++ b/include/swift/Reflection/ReflectionContext.h
@@ -34,7 +34,6 @@
 #include "swift/Runtime/Unreachable.h"
 
 #include <set>
-#include <sstream>
 #include <unordered_map>
 #include <utility>
 #include <vector>
@@ -946,10 +945,12 @@ class ReflectionContext
           reinterpret_cast<const MetadataAllocationBacktraceHeader<Runtime> *>(
               HeaderBytes.get());
       if (HeaderPtr == nullptr) {
-        std::stringstream stream;
-        stream << "unable to read Next pointer 0x" << std::hex
-               << BacktraceListNext.getAddressData();
-        return stream.str();
+        // FIXME: std::stringstream would be better, but LLVM's standard library
+        // introduces a vtable and we don't want that.
+        char result[128];
+        std::snprintf(result, sizeof(result), "unable to read Next pointer %p",
+            BacktraceListNext.getAddressData());
+        return std::string(result);
       }
       auto BacktraceAddrPtr =
           BacktraceListNext +