From c9efa69ef19c6a4b448cf16f50c8dc7ed91978f2 Mon Sep 17 00:00:00 2001
From: Alastair Houghton <ahoughton@apple.com>
Date: Wed, 27 Sep 2023 09:56:22 +0100
Subject: [PATCH] [Linux] Make the backtracing symbol reference conditional.

On the LSan builds, we disable the backtracer, which results in a
link error because we completely remove the code from libswiftCore.

rdar://116105222
---
 stdlib/public/runtime/CMakeLists.txt       | 14 +++++++++++---
 stdlib/public/runtime/SwiftRT-ELF-WASM.cpp |  2 ++
 2 files changed, 13 insertions(+), 3 deletions(-)

diff --git a/stdlib/public/runtime/CMakeLists.txt b/stdlib/public/runtime/CMakeLists.txt
index d913e337fb6f2..13a0451a41a4b 100644
--- a/stdlib/public/runtime/CMakeLists.txt
+++ b/stdlib/public/runtime/CMakeLists.txt
@@ -100,8 +100,10 @@ set(LLVM_OPTIONAL_SOURCES
     ${swift_runtime_leaks_sources}
     ${swift_runtime_backtracing_sources})
 
+set(swift_enable_backtracing)
 if(SWIFT_ENABLE_BACKTRACING)
   list(APPEND swift_runtime_sources ${swift_runtime_backtracing_sources})
+  set(swift_enable_backtracing -DSWIFT_ENABLE_BACKTRACING)
 endif()
 
 set(swift_runtime_library_compile_flags ${swift_runtime_compile_flags})
@@ -172,7 +174,9 @@ endforeach()
 add_swift_target_library(swiftImageRegistrationObjectELF
                   OBJECT_LIBRARY IS_STDLIB IS_STDLIB_CORE
                   SwiftRT-ELF-WASM.cpp
-                  C_COMPILE_FLAGS ${SWIFT_RUNTIME_CORE_CXX_FLAGS}
+                  C_COMPILE_FLAGS
+                    ${SWIFT_RUNTIME_CORE_CXX_FLAGS}
+                    ${swift_enable_backtracing}
                   C_COMPILE_FLAGS_LINUX -fno-lto
                   LINK_FLAGS ${SWIFT_RUNTIME_CORE_LINK_FLAGS}
                   TARGET_SDKS ${ELFISH_SDKS}
@@ -183,7 +187,9 @@ add_swift_target_library(swiftImageRegistrationObjectELF
 add_swift_target_library(swiftImageRegistrationObjectCOFF
                   OBJECT_LIBRARY IS_STDLIB IS_STDLIB_CORE
                   SwiftRT-COFF.cpp
-                  C_COMPILE_FLAGS ${SWIFT_RUNTIME_CORE_CXX_FLAGS}
+                  C_COMPILE_FLAGS
+                    ${SWIFT_RUNTIME_CORE_CXX_FLAGS}
+                    ${swift_enable_backtracing}
                   LINK_FLAGS ${SWIFT_RUNTIME_CORE_LINK_FLAGS}
                   TARGET_SDKS ${COFF_SDKS}
                   SWIFT_COMPILE_FLAGS ${SWIFT_STANDARD_LIBRARY_SWIFT_FLAGS}
@@ -192,7 +198,9 @@ add_swift_target_library(swiftImageRegistrationObjectCOFF
 add_swift_target_library(swiftImageRegistrationObjectWASM
                   OBJECT_LIBRARY IS_STDLIB IS_STDLIB_CORE
                   SwiftRT-ELF-WASM.cpp
-                  C_COMPILE_FLAGS ${SWIFT_RUNTIME_CORE_CXX_FLAGS}
+                  C_COMPILE_FLAGS
+                    ${SWIFT_RUNTIME_CORE_CXX_FLAGS}
+                    ${swift_enable_backtracing}
                   LINK_FLAGS ${SWIFT_RUNTIME_CORE_LINK_FLAGS}
                   TARGET_SDKS ${WASM_SDKS}
                   SWIFT_COMPILE_FLAGS ${SWIFT_STANDARD_LIBRARY_SWIFT_FLAGS}
diff --git a/stdlib/public/runtime/SwiftRT-ELF-WASM.cpp b/stdlib/public/runtime/SwiftRT-ELF-WASM.cpp
index ff3ac5b192a4a..cbb0b7641d896 100644
--- a/stdlib/public/runtime/SwiftRT-ELF-WASM.cpp
+++ b/stdlib/public/runtime/SwiftRT-ELF-WASM.cpp
@@ -25,10 +25,12 @@ extern "C" const char __dso_handle[];
 static constexpr const void *__dso_handle = nullptr;
 #endif
 
+#if SWIFT_ENABLE_BACKTRACING
 // Drag in a symbol from the backtracer, to force the static linker to include
 // the code.
 static const void *__backtraceRef __attribute__((used))
   = (const void *)swift::runtime::backtrace::_swift_backtrace_isThunkFunction;
+#endif
 
 // Create empty sections to ensure that the start/stop symbols are synthesized
 // by the linker.  Otherwise, we may end up with undefined symbol references as