[clang-repl] Disable building when LLVM_STATIC_LINK_CXX_STDLIB is ON.

We have seen random symbol not found "__cxa_throw" error in fuschia build bots and out-of-tree users. The understanding have been that they are built without exception support, but it turned out that these platforms have LLVM_STATIC_LINK_CXX_STDLIB ON so that they link libstdc++ to llvm statically. The reason why this is problematic for clang-repl is that by default clang-repl tries to find symbols from symbol table of executable and dynamic libraries loaded by current process. It needs to load another libstdc++, but the platform that had LLVM_STATIC_LINK_CXX_STDLIB turned on is usally those with missing or obsolate shared libstdc++ in the first place -- trying to load it again would be destined to fail eventually with a risk to introuduce mixed libstdc++ versions.

A proper solution that doesn't take a workaround is statically link the same libstdc++ by clang-repl side, but this is not possible with old JIT linker runtimedyld. New just-in-time linker JITLink handles this relatively well, but it's not availalbe in majority of platforms. For now, this patch just disables the building of clang-repl when LLVM_STATIC_LINK_CXX_STDLIB is ON and removes the "__cxa_throw" check in exception unittest as well as reverting previous exception check flag patch.

Reviewed By: v.g.vassilev

Differential Revision: https://reviews.llvm.org/D130788

clang/CMakeLists.txt

@@ -504,6 +504,13 @@ CMAKE_DEPENDENT_OPTION(CLANG_PLUGIN_SUPPORT
   "Build clang with plugin support" ON
   "HAVE_CLANG_PLUGIN_SUPPORT" OFF)
 
+# If libstdc++ is statically linked, clang-repl needs to statically link libstdc++
+# itself, which is not possible in many platforms because of current limitations in 
+# JIT stack. (more platforms need to be supported by JITLink)
+if(NOT LLVM_STATIC_LINK_CXX_STDLIB)
+  set(HAVE_CLANG_REPL_SUPPORT ON)
+endif()
+
 option(CLANG_ENABLE_ARCMT "Build ARCMT." ON)
 option(CLANG_ENABLE_STATIC_ANALYZER
   "Include static analyzer in clang binary." ON)

clang/test/CMakeLists.txt

@@ -66,7 +66,6 @@ list(APPEND CLANG_TEST_DEPS
   clang-import-test
   clang-rename
   clang-refactor
-  clang-repl
   clang-diff
   clang-scan-deps
   diagtool
@@ -147,6 +146,12 @@ if(CLANG_ENABLE_STATIC_ANALYZER)
   endif()
 endif()
 
+if (HAVE_CLANG_REPL_SUPPORT)
+  list(APPEND CLANG_TEST_DEPS
+    clang-repl
+    )
+endif()
+
 # Copy gen_ast_dump_json_test.py to the clang build dir. This allows invoking
 # it without having to pass the --clang= argument
 configure_file(AST/gen_ast_dump_json_test.py

clang/test/Interpreter/code-undo.cpp

@@ -1,6 +1,5 @@
 // RUN: clang-repl "int i = 10;" 'extern "C" int printf(const char*,...);' \
 // RUN:            'auto r1 = printf("i = %d\n", i);' | FileCheck --check-prefix=CHECK-DRIVER %s
-// REQUIRES: host-supports-jit
 // UNSUPPORTED: system-aix
 // CHECK-DRIVER: i = 10
 // RUN: cat %s | clang-repl | FileCheck %s

clang/test/Interpreter/execute-weak.cpp

@@ -1,7 +1,6 @@
 // RUN: clang-repl "int x = 10;" "int y=7; err;" "int y = 10;"
 // RUN: clang-repl "int i = 10;" 'extern "C" int printf(const char*,...);' \
 // RUN:            'auto r1 = printf("i = %d\n", i);' | FileCheck --check-prefix=CHECK-DRIVER %s
-// REQUIRES: host-supports-jit
 // CHECK-DRIVER: i = 10
 // UNSUPPORTED: system-aix, system-windows
 // RUN: cat %s | clang-repl | FileCheck %s

clang/test/Interpreter/execute.cpp

@@ -2,7 +2,6 @@
 // RUN: clang-repl "int x = 10;" "int y=7; err;" "int y = 10;"
 // RUN: clang-repl "int i = 10;" 'extern "C" int printf(const char*,...);' \
 // RUN:            'auto r1 = printf("i = %d\n", i);' | FileCheck --check-prefix=CHECK-DRIVER %s
-// REQUIRES: host-supports-jit
 // UNSUPPORTED: system-aix
 // CHECK-DRIVER: i = 10
 // RUN: cat %s | clang-repl | FileCheck %s

clang/test/Interpreter/global-dtor-win.cpp

@@ -1,14 +0,0 @@
-// clang-format off
-// FIXME: Merge into global-dtor.cpp when exception support arrives on windows-msvc
-// REQUIRES: host-supports-jit && windows-msvc
-//
-// Tests that a global destructor is ran in windows-msvc platform.
-//
-// RUN: cat %s | clang-repl | FileCheck %s
-
-extern "C" int printf(const char *, ... );
-
-struct D { float f = 1.0; D *m = nullptr; D(){} ~D() { printf("D[f=%f, m=0x%llx]\n", f, reinterpret_cast<unsigned long long>(m)); }} d;
-// CHECK: D[f=1.000000, m=0x0]
-
-%quit

clang/test/Interpreter/global-dtor.cpp

@@ -1,5 +1,4 @@
 // clang-format off
-// REQUIRES: host-supports-jit, host-supports-exception 
 // UNSUPPORTED: system-aix
 //
 // Tests that a global destructor is ran on platforms with gnu exception support.

clang/test/Interpreter/lit.local.cfg

@@ -0,0 +1,2 @@
+if 'host-supports-jit' not in config.available_features:
+    config.unsupported = True

clang/test/Interpreter/plugins.cpp

@@ -1,7 +1,7 @@
 // RUN: cat %s | clang-repl -Xcc -Xclang -Xcc -load -Xcc -Xclang \
 // RUN:            -Xcc %llvmshlibdir/PrintFunctionNames%pluginext -Xcc -Xclang\
 // RUN:            -Xcc -add-plugin -Xcc -Xclang -Xcc print-fns 2>&1 | FileCheck %s
-// REQUIRES: host-supports-jit, plugins, examples
+// REQUIRES: plugins, examples
 
 int i = 10;
 extern "C" int printf(const char*,...);

clang/test/Interpreter/simple-exception.cpp

@@ -1,5 +1,4 @@
 // clang-format off
-// REQUIRES: host-supports-jit, host-supports-exception 
 // UNSUPPORTED: system-aix
 // XFAIL: arm, arm64-apple, windows-msvc, windows-gnu
 // RUN: cat %s | clang-repl | FileCheck %s

clang/test/lit.cfg.py

@@ -74,7 +74,6 @@ def have_host_jit_feature_support(feature_name):
     clang_repl_exe = lit.util.which('clang-repl', config.clang_tools_dir)
 
     if not clang_repl_exe:
-        print('clang-repl not found')
         return False
 
     try:
@@ -92,9 +91,6 @@ def have_host_jit_feature_support(feature_name):
 if have_host_jit_feature_support('jit'):
     config.available_features.add('host-supports-jit')
 
-if have_host_jit_feature_support('exception'):
-    config.available_features.add('host-supports-exception')
-
 if config.clang_staticanalyzer:
     config.available_features.add('staticanalyzer')
     tools.append('clang-check')

clang/tools/CMakeLists.txt

@@ -14,7 +14,9 @@ add_clang_subdirectory(clang-offload-packager)
 add_clang_subdirectory(clang-offload-bundler)
 add_clang_subdirectory(clang-offload-wrapper)
 add_clang_subdirectory(clang-scan-deps)
-add_clang_subdirectory(clang-repl)
+if(HAVE_CLANG_REPL_SUPPORT)
+  add_clang_subdirectory(clang-repl)
+endif()
 
 add_clang_subdirectory(c-index-test)
 

clang/tools/clang-repl/ClangRepl.cpp

@@ -28,8 +28,6 @@ static llvm::cl::list<std::string>
               llvm::cl::CommaSeparated);
 static llvm::cl::opt<bool> OptHostSupportsJit("host-supports-jit",
                                               llvm::cl::Hidden);
-static llvm::cl::opt<bool> OptHostSupportsException("host-supports-exception",
-                                                    llvm::cl::Hidden);
 static llvm::cl::list<std::string> OptInputs(llvm::cl::Positional,
                                              llvm::cl::desc("[code to run]"));
 
@@ -67,42 +65,6 @@ static int checkDiagErrors(const clang::CompilerInstance *CI) {
   return Errs ? EXIT_FAILURE : EXIT_SUCCESS;
 }
 
-// Check if the host environment supports c++ exception handling
-// by querying the existence of symbol __cxa_throw.
-static bool checkExceptionSupport() {
-  auto J = llvm::orc::LLJITBuilder().create();
-  if (!J) {
-    llvm::consumeError(J.takeError());
-    return false;
-  }
-
-  std::vector<const char *> Dummy;
-  auto CI = clang::IncrementalCompilerBuilder::create(Dummy);
-  if (!CI) {
-    llvm::consumeError(CI.takeError());
-    return false;
-  }
-
-  auto Interp = clang::Interpreter::create(std::move(*CI));
-  if (!Interp) {
-    llvm::consumeError(Interp.takeError());
-    return false;
-  }
-
-  if (auto Err = (*Interp)->ParseAndExecute("")) {
-    llvm::consumeError(std::move(Err));
-    return false;
-  }
-
-  auto Sym = (*Interp)->getSymbolAddress("__cxa_throw");
-  if (!Sym) {
-    llvm::consumeError(Sym.takeError());
-    return false;
-  }
-
-  return true;
-}
-
 llvm::ExitOnError ExitOnErr;
 int main(int argc, const char **argv) {
   ExitOnErr.setBanner("clang-repl: ");
@@ -127,14 +89,6 @@ int main(int argc, const char **argv) {
     return 0;
   }
 
-  if (OptHostSupportsException) {
-    if (checkExceptionSupport())
-      llvm::outs() << "true\n";
-    else
-      llvm::outs() << "false\n";
-    return 0;
-  }
-
   // FIXME: Investigate if we could use runToolOnCodeWithArgs from tooling. It
   // can replace the boilerplate code for creation of the compiler instance.
   auto CI = ExitOnErr(clang::IncrementalCompilerBuilder::create(ClangArgv));

clang/unittests/CMakeLists.txt

@@ -35,7 +35,9 @@ add_subdirectory(Frontend)
 add_subdirectory(Rewrite)
 add_subdirectory(Sema)
 add_subdirectory(CodeGen)
-add_subdirectory(Interpreter)
+if(HAVE_CLANG_REPL_SUPPORT)
+  add_subdirectory(Interpreter)
+endif()
 # FIXME: libclang unit tests are disabled on Windows due
 # to failures, mostly in libclang.VirtualFileOverlay_*.
 if(NOT WIN32 AND CLANG_TOOL_LIBCLANG_BUILD) 

clang/unittests/Interpreter/ExceptionTests/InterpreterExceptionTest.cpp

@@ -113,17 +113,6 @@ extern "C" int throw_exception() {
                               Triple.getArch() == llvm::Triple::aarch64_32))
     return;
 
-  // Check if platform does not support exceptions.
-  {
-    // Force the creation of an incremental executor to call getSymbolAddress.
-    llvm::cantFail(Interp->ParseAndExecute(""));
-    auto Sym = Interp->getSymbolAddress("__cxa_throw");
-    if (!Sym) {
-      LLVMConsumeError(llvm::wrap(Sym.takeError()));
-      return;
-    }
-  }
-
   llvm::cantFail(Interp->ParseAndExecute(ExceptionCode));
   testing::internal::CaptureStdout();
   auto ThrowException =