danalbert updated this revision to Diff 118711.
danalbert added a comment.
Herald added a subscriber: mgorny.
Update the test with an XFAIL when _LIBCXX_DYNAMIC_FALLBACK is not set.
https://reviews.llvm.org/D38827 adds this cmake option to libc++.
https://reviews.llvm.org/D38599
Files:
CMakeLists.txt
src/private_typeinfo.cpp
test/CMakeLists.txt
test/dlopen_dynamic_cast.sh.cpp
test/libcxxabi/test/config.py
test/lit.site.cfg.in
Index: test/lit.site.cfg.in
===================================================================
--- test/lit.site.cfg.in
+++ test/lit.site.cfg.in
@@ -16,6 +16,7 @@
config.executor = "@LIBCXXABI_EXECUTOR@"
config.libcxxabi_shared = "@LIBCXXABI_ENABLE_SHARED@"
config.enable_shared = "@LIBCXX_ENABLE_SHARED@"
+config.dynamic_fallback = "@LIBCXX_DYNAMIC_FALLBACK@"
config.enable_exceptions = "@LIBCXXABI_ENABLE_EXCEPTIONS@"
config.host_triple = "@LLVM_HOST_TRIPLE@"
config.target_triple = "@TARGET_TRIPLE@"
Index: test/libcxxabi/test/config.py
===================================================================
--- test/libcxxabi/test/config.py
+++ test/libcxxabi/test/config.py
@@ -48,6 +48,11 @@
if not self.get_lit_bool('llvm_unwinder', False):
self.config.available_features.add('libcxxabi-has-system-unwinder')
+ if self.get_lit_bool('dynamic_fallback', False):
+ self.config.available_features.add('libcxx-dynamic-fallback')
+ else:
+ self.config.available_features.add('libcxx-no-dynamic-fallback')
+
def configure_compile_flags(self):
self.cxx.compile_flags += ['-DLIBCXXABI_NO_TIMER']
if self.get_lit_bool('enable_exceptions', True):
Index: test/dlopen_dynamic_cast.sh.cpp
===================================================================
--- /dev/null
+++ test/dlopen_dynamic_cast.sh.cpp
@@ -0,0 +1,89 @@
+//===-------------------- dlopen_dynamic_cast.sh.cpp ----------------------===//
+//
+// The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+// type_infos are not coalesced across dlopen boundaries when RTLD_LOCAL is
+// used, as is common in plugin interfaces and JNI libraries. For dynamic_cast
+// to work across a dlopen boundary, we must use a string comparison of the type
+// names instead of a pointer comparison of the type_infos.
+// https://reviews.llvm.org/D38599
+
+// XFAIL: libcxx-no-dynamic-fallback
+
+// RUN: %cxx %flags %compile_flags -DBUILD_BASE -fPIC -c %s -o %T/base.o
+// RUN: %cxx %flags %link_flags -shared %T/base.o -o %T/libbase.so
+// RUN: %cxx %flags %compile_flags -DBUILD_TEST -fPIC -c %s -o %T/test.o
+// RUN: %cxx %flags %link_flags -shared %T/test.o -o %T/libtest.so -L%T -lbase
+// RUN: %cxx %flags %compile_flags -DBUILD_EXE -c %s -o %t.o
+// RUN: %cxx %flags %link_flags %t.o -o %t.exe -ldl
+// RUN: LD_LIBRARY_PATH=%T %t.exe
+
+class Base {
+public:
+ virtual ~Base(){};
+};
+
+class BaseImpl : public Base {
+public:
+ BaseImpl();
+};
+
+#ifdef BUILD_BASE
+BaseImpl::BaseImpl() {}
+#endif
+
+#ifdef BUILD_TEST
+extern "C" bool do_test() {
+ BaseImpl base_impl;
+ Base* base = &base_impl;
+ return dynamic_cast<BaseImpl*>(base) != nullptr;
+}
+#endif
+
+#ifdef BUILD_EXE
+#include <dlfcn.h>
+#include <stdio.h>
+#include <stdlib.h>
+
+typedef bool (*test_func)();
+
+void* load_library(const char* name) {
+ void* lib = dlopen(name, RTLD_NOW | RTLD_LOCAL);
+ if (lib == nullptr) {
+ fprintf(stderr, "dlopen %s failed: %s\n", name, dlerror());
+ abort();
+ }
+ return lib;
+}
+
+test_func load_func(void* lib, const char* name) {
+ test_func sym = reinterpret_cast<test_func>(dlsym(lib, name));
+ if (sym == nullptr) {
+ fprintf(stderr, "dlsym %s failed: %s\n", name, dlerror());
+ abort();
+ }
+ return sym;
+}
+
+int main(int argc, char**) {
+ // Explicitly loading libbase.so before libtest.so causes the test to fail
+ // because the type_infos do not get coalesced.
+ load_library("libbase.so");
+
+ void* libtest = load_library("libtest.so");
+ test_func do_test = load_func(libtest, "do_test");
+
+ if (!do_test()) {
+ fprintf(stderr, "do_test() failed!\n");
+ return EXIT_FAILURE;
+ } else {
+ fprintf(stderr, "do_test() passed!\n");
+ return EXIT_SUCCESS;
+ }
+}
+#endif
Index: test/CMakeLists.txt
===================================================================
--- test/CMakeLists.txt
+++ test/CMakeLists.txt
@@ -18,6 +18,7 @@
pythonize_bool(LIBCXXABI_ENABLE_EXCEPTIONS)
pythonize_bool(LIBCXXABI_USE_LLVM_UNWINDER)
pythonize_bool(LIBCXXABI_BUILD_EXTERNAL_THREAD_LIBRARY)
+pythonize_bool(LIBCXX_DYNAMIC_FALLBACK)
set(LIBCXXABI_TARGET_INFO "libcxx.test.target_info.LocalTI" CACHE STRING
"TargetInfo to use when setting up test environment.")
set(LIBCXXABI_EXECUTOR "None" CACHE STRING
Index: src/private_typeinfo.cpp
===================================================================
--- src/private_typeinfo.cpp
+++ src/private_typeinfo.cpp
@@ -10,39 +10,19 @@
#include "private_typeinfo.h"
// The flag _LIBCXX_DYNAMIC_FALLBACK is used to make dynamic_cast more
-// forgiving when type_info's mistakenly have hidden visibility and thus
-// multiple type_infos can exist for a single type.
-//
+// forgiving when multiple type_infos exist for a single type. This happens if
+// the libraries are mistakenly built with the type_infos having hidden
+// visibility, but also occurs when the libraries are loaded with dlopen.
+//
// When _LIBCXX_DYNAMIC_FALLBACK is defined, and only in the case where
// there is a detected inconsistency in the type_info hierarchy during a
// dynamic_cast, then the equality operation will fall back to using strcmp
// on type_info names to determine type_info equality.
-//
-// This change happens *only* under dynamic_cast, and only when
-// dynamic_cast is faced with the choice: abort, or possibly give back the
-// wrong answer. If when the dynamic_cast is done with this fallback
-// algorithm and an inconsistency is still detected, dynamic_cast will call
-// abort with an appropriate message.
-//
-// The current implementation of _LIBCXX_DYNAMIC_FALLBACK requires a
-// printf-like function called syslog:
-//
-// void syslog(int facility_priority, const char* format, ...);
-//
-// If you want this functionality but your platform doesn't have syslog,
-// just implement it in terms of fprintf(stderr, ...).
-//
+//
// _LIBCXX_DYNAMIC_FALLBACK is currently off by default.
-
#include <string.h>
-
-#ifdef _LIBCXX_DYNAMIC_FALLBACK
-#include "abort_message.h"
-#include <sys/syslog.h>
-#endif
-
// On Windows, typeids are different between DLLs and EXEs, so comparing
// type_info* will work for typeids from the same compiled file but fail
// for typeids from a DLL and an executable. Among other things, exceptions
@@ -647,11 +627,11 @@
// find (static_ptr, static_type), either on a public or private path
if (info.path_dst_ptr_to_static_ptr == unknown)
{
- // We get here only if there is some kind of visibility problem
- // in client code.
- syslog(LOG_ERR, "dynamic_cast error 1: Both of the following type_info's "
- "should have public visibility. At least one of them is hidden. %s"
- ", %s.\n", static_type->name(), dynamic_type->name());
+ // We get here only if there is some kind of visibility problem in
+ // client code. Possibly because the binaries were built
+ // incorrectly, but possibly because the library was loaded with
+ // dlopen.
+ //
// Redo the search comparing type_info's using strcmp
info = {dst_type, static_ptr, static_type, src2dst_offset, 0};
info.number_of_dst_type = 1;
@@ -672,10 +652,6 @@
if (info.path_dst_ptr_to_static_ptr == unknown &&
info.path_dynamic_ptr_to_static_ptr == unknown)
{
- syslog(LOG_ERR, "dynamic_cast error 2: One or more of the following type_info's "
- " has hidden visibility. They should all have public visibility. "
- " %s, %s, %s.\n", static_type->name(), dynamic_type->name(),
- dst_type->name());
// Redo the search comparing type_info's using strcmp
info = {dst_type, static_ptr, static_type, src2dst_offset, 0};
dynamic_type->search_below_dst(&info, dynamic_ptr, public_path, true);
Index: CMakeLists.txt
===================================================================
--- CMakeLists.txt
+++ CMakeLists.txt
@@ -400,6 +400,10 @@
add_definitions(-DLIBCXXABI_BAREMETAL)
endif()
+if (LIBCXX_DYNAMIC_FALLBACK)
+ add_definitions(-D_LIBCXX_DYNAMIC_FALLBACK)
+endif()
+
string(REPLACE ";" " " LIBCXXABI_CXX_FLAGS "${LIBCXXABI_CXX_FLAGS}")
set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} ${LIBCXXABI_CXX_FLAGS}")
set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} ${LIBCXXABI_C_FLAGS}")
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