Changes imported from Abseil "staging" branch:

- db061dd2b795837e6154be0991077ca5a03ec471 Release the async-signal safe demangler as an internal im... by Derek Mauro <dmauro@google.com>
  - 310440eb33d946df79d26bf1edf795f6a0b466b9 Use static_cast to constrain nanoseconds to int range, av... by Abseil Team <absl-team@google.com>

GitOrigin-RevId: db061dd2b795837e6154be0991077ca5a03ec471
Change-Id: Ibc1bc1db355a48115451da5ce88d66a1f6e1a182

absl/base/internal/spinlock_wait.cc

@@ -72,7 +72,7 @@ int SpinLockSuggestedDelayNS(int loop) {
   // Mean is exponential in loop for first 32 iterations, then 8ms.
   // The futex path multiplies this by 16, since we expect explicit wakeups
   // almost always on that path.
-  return r >> (44 - (loop >> 3));
+  return static_cast<int>(r >> (44 - (loop >> 3)));
 }
 
 }  // namespace base_internal

absl/debugging/BUILD.bazel

@@ -64,10 +64,34 @@ cc_library(
     deps = [
         "//absl/base",
         "//absl/base:dynamic_annotations",
+    ],
+)
+
+cc_library(
+    name = "demangle_internal",
+    srcs = ["internal/demangle.cc"],
+    hdrs = ["internal/demangle.h"],
+    copts = ABSL_DEFAULT_COPTS,
+    deps = [
+        "//absl/base",
         "//absl/base:core_headers",
     ],
 )
 
+cc_test(
+    name = "demangle_test",
+    srcs = ["internal/demangle_test.cc"],
+    copts = ABSL_TEST_COPTS,
+    deps = [
+        ":demangle_internal",
+        ":stack_consumption",
+        "//absl/base",
+        "//absl/base:core_headers",
+        "//absl/memory",
+        "@com_google_googletest//:gtest_main",
+    ],
+)
+
 cc_library(
     name = "leak_check",
     srcs = select({

absl/debugging/CMakeLists.txt

@@ -22,6 +22,7 @@ list(APPEND DEBUGGING_PUBLIC_HEADERS
 
 list(APPEND DEBUGGING_INTERNAL_HEADERS
   "internal/address_is_readable.h"
+  "internal/demangle.h"
   "internal/elf_mem_image.h"
   "internal/stacktrace_config.h"
   "internal/vdso_support.h"
@@ -31,6 +32,7 @@ list(APPEND DEBUGGING_INTERNAL_HEADERS
 list(APPEND STACKTRACE_SRC
   "stacktrace.cc"
   "internal/address_is_readable.cc"
+  "internal/demangle.cc"
   "internal/elf_mem_image.cc"
   "internal/vdso_support.cc"
   ${DEBUGGING_PUBLIC_HEADERS}
@@ -79,6 +81,41 @@ absl_header_library(
 ## TESTS
 #
 
+list(APPEND DEBUGGING_INTERNAL_TEST_HEADERS
+  "internal/stack_consumption.h"
+)
+
+list(APPEND STACK_CONSUMPTION_SRC
+  "internal/stack_consumption.cc"
+  ${DEBUGGING_INTERNAL_TEST_HEADERS}
+)
+
+absl_library(
+  TARGET
+    absl_stack_consumption
+  SOURCES
+    ${STACK_CONSUMPTION_SRC}
+)
+
+absl_test(
+  TARGET
+    absl_stack_consumption_test
+  SOURCES
+    ${STACK_CONSUMPTION_SRC}
+)
+
+list(APPEND DEMANGLE_TEST_SRC "demangle_test.cc")
+
+absl_test(
+  TARGET
+    demangle_test
+  SOURCES
+    ${DEMANGLE_TEST_SRC}
+  PUBLIC_LIBRARIES
+    absl_stacktrace absl_stack_consumption
+)
+
+
 # test leak_check_test
 list(APPEND LEAK_CHECK_TEST_SRC "leak_check_test.cc")
 
@@ -90,4 +127,3 @@ absl_test(
   PUBLIC_LIBRARIES
     absl_leak_check
 )
-

absl/debugging/internal/demangle.h

@@ -0,0 +1,67 @@
+// Copyright 2018 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// An async-signal-safe and thread-safe demangler for Itanium C++ ABI
+// (aka G++ V3 ABI).
+//
+// The demangler is implemented to be used in async signal handlers to
+// symbolize stack traces.  We cannot use libstdc++'s
+// abi::__cxa_demangle() in such signal handlers since it's not async
+// signal safe (it uses malloc() internally).
+//
+// Note that this demangler doesn't support full demangling.  More
+// specifically, it doesn't print types of function parameters and
+// types of template arguments.  It just skips them.  However, it's
+// still very useful to extract basic information such as class,
+// function, constructor, destructor, and operator names.
+//
+// See the implementation note in demangle.cc if you are interested.
+//
+// Example:
+//
+// | Mangled Name  | The Demangler | abi::__cxa_demangle()
+// |---------------|---------------|-----------------------
+// | _Z1fv         | f()           | f()
+// | _Z1fi         | f()           | f(int)
+// | _Z3foo3bar    | foo()         | foo(bar)
+// | _Z1fIiEvi     | f<>()         | void f<int>(int)
+// | _ZN1N1fE      | N::f          | N::f
+// | _ZN3Foo3BarEv | Foo::Bar()    | Foo::Bar()
+// | _Zrm1XS_"     | operator%()   | operator%(X, X)
+// | _ZN3FooC1Ev   | Foo::Foo()    | Foo::Foo()
+// | _Z1fSs        | f()           | f(std::basic_string<char,
+// |               |               |   std::char_traits<char>,
+// |               |               |   std::allocator<char> >)
+//
+// See the unit test for more examples.
+//
+// Note: we might want to write demanglers for ABIs other than Itanium
+// C++ ABI in the future.
+//
+
+#ifndef ABSL_DEBUGGING_INTERNAL_DEMANGLE_H_
+#define ABSL_DEBUGGING_INTERNAL_DEMANGLE_H_
+
+namespace absl {
+namespace debugging_internal {
+
+// Demangle `mangled`.  On success, return true and write the
+// demangled symbol name to `out`.  Otherwise, return false.
+// `out` is modified even if demangling is unsuccessful.
+bool Demangle(const char *mangled, char *out, int out_size);
+
+}  // namespace debugging_internal
+}  // namespace absl
+
+#endif  // ABSL_DEBUGGING_INTERNAL_DEMANGLE_H_

absl/debugging/internal/demangle_test.cc

@@ -0,0 +1,191 @@
+// Copyright 2018 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "absl/debugging/internal/demangle.h"
+
+#include <cstdlib>
+#include <string>
+
+#include "gtest/gtest.h"
+#include "absl/base/internal/raw_logging.h"
+#include "absl/debugging/internal/stack_consumption.h"
+#include "absl/memory/memory.h"
+
+namespace absl {
+namespace debugging_internal {
+namespace {
+
+// A wrapper function for Demangle() to make the unit test simple.
+static const char *DemangleIt(const char * const mangled) {
+  static char demangled[4096];
+  if (Demangle(mangled, demangled, sizeof(demangled))) {
+    return demangled;
+  } else {
+    return mangled;
+  }
+}
+
+// Test corner cases of bounary conditions.
+TEST(Demangle, CornerCases) {
+  char tmp[10];
+  EXPECT_TRUE(Demangle("_Z6foobarv", tmp, sizeof(tmp)));
+  // sizeof("foobar()") == 9
+  EXPECT_STREQ("foobar()", tmp);
+  EXPECT_TRUE(Demangle("_Z6foobarv", tmp, 9));
+  EXPECT_STREQ("foobar()", tmp);
+  EXPECT_FALSE(Demangle("_Z6foobarv", tmp, 8));  // Not enough.
+  EXPECT_FALSE(Demangle("_Z6foobarv", tmp, 1));
+  EXPECT_FALSE(Demangle("_Z6foobarv", tmp, 0));
+  EXPECT_FALSE(Demangle("_Z6foobarv", nullptr, 0));  // Should not cause SEGV.
+  EXPECT_FALSE(Demangle("_Z1000000", tmp, 9));
+}
+
+// Test handling of functions suffixed with .clone.N, which is used
+// by GCC 4.5.x (and our locally-modified version of GCC 4.4.x), and
+// .constprop.N and .isra.N, which are used by GCC 4.6.x.  These
+// suffixes are used to indicate functions which have been cloned
+// during optimization.  We ignore these suffixes.
+TEST(Demangle, Clones) {
+  char tmp[20];
+  EXPECT_TRUE(Demangle("_ZL3Foov", tmp, sizeof(tmp)));
+  EXPECT_STREQ("Foo()", tmp);
+  EXPECT_TRUE(Demangle("_ZL3Foov.clone.3", tmp, sizeof(tmp)));
+  EXPECT_STREQ("Foo()", tmp);
+  EXPECT_TRUE(Demangle("_ZL3Foov.constprop.80", tmp, sizeof(tmp)));
+  EXPECT_STREQ("Foo()", tmp);
+  EXPECT_TRUE(Demangle("_ZL3Foov.isra.18", tmp, sizeof(tmp)));
+  EXPECT_STREQ("Foo()", tmp);
+  EXPECT_TRUE(Demangle("_ZL3Foov.isra.2.constprop.18", tmp, sizeof(tmp)));
+  EXPECT_STREQ("Foo()", tmp);
+  // Invalid (truncated), should not demangle.
+  EXPECT_FALSE(Demangle("_ZL3Foov.clo", tmp, sizeof(tmp)));
+  // Invalid (.clone. not followed by number), should not demangle.
+  EXPECT_FALSE(Demangle("_ZL3Foov.clone.", tmp, sizeof(tmp)));
+  // Invalid (.clone. followed by non-number), should not demangle.
+  EXPECT_FALSE(Demangle("_ZL3Foov.clone.foo", tmp, sizeof(tmp)));
+  // Invalid (.constprop. not followed by number), should not demangle.
+  EXPECT_FALSE(Demangle("_ZL3Foov.isra.2.constprop.", tmp, sizeof(tmp)));
+}
+
+// Tests that verify that Demangle footprint is within some limit.
+// They are not to be run under sanitizers as the sanitizers increase
+// stack consumption by about 4x.
+#if defined(ABSL_INTERNAL_HAVE_DEBUGGING_STACK_CONSUMPTION) && \
+    !ADDRESS_SANITIZER && !MEMORY_SANITIZER && !THREAD_SANITIZER
+
+static const char *g_mangled;
+static char g_demangle_buffer[4096];
+static char *g_demangle_result;
+
+static void DemangleSignalHandler(int signo) {
+  if (Demangle(g_mangled, g_demangle_buffer, sizeof(g_demangle_buffer))) {
+    g_demangle_result = g_demangle_buffer;
+  } else {
+    g_demangle_result = nullptr;
+  }
+}
+
+// Call Demangle and figure out the stack footprint of this call.
+static const char *DemangleStackConsumption(const char *mangled,
+                                            int *stack_consumed) {
+  g_mangled = mangled;
+  *stack_consumed = GetSignalHandlerStackConsumption(DemangleSignalHandler);
+  ABSL_RAW_LOG(INFO, "Stack consumption of Demangle: %d", *stack_consumed);
+  return g_demangle_result;
+}
+
+// Demangle stack consumption should be within 8kB for simple mangled names
+// with some level of nesting. With alternate signal stack we have 64K,
+// but some signal handlers run on thread stack, and could have arbitrarily
+// little space left (so we don't want to make this number too large).
+const int kStackConsumptionUpperLimit = 8192;
+
+// Returns a mangled name nested to the given depth.
+static std::string NestedMangledName(int depth) {
+  std::string mangled_name = "_Z1a";
+  if (depth > 0) {
+    mangled_name += "IXL";
+    mangled_name += NestedMangledName(depth - 1);
+    mangled_name += "EEE";
+  }
+  return mangled_name;
+}
+
+TEST(Demangle, DemangleStackConsumption) {
+  // Measure stack consumption of Demangle for nested mangled names of varying
+  // depth.  Since Demangle is implemented as a recursive descent parser,
+  // stack consumption will grow as the nesting depth increases.  By measuring
+  // the stack consumption for increasing depths, we can see the growing
+  // impact of any stack-saving changes made to the code for Demangle.
+  int stack_consumed = 0;
+
+  const char *demangled =
+      DemangleStackConsumption("_Z6foobarv", &stack_consumed);
+  EXPECT_STREQ("foobar()", demangled);
+  EXPECT_GT(stack_consumed, 0);
+  EXPECT_LT(stack_consumed, kStackConsumptionUpperLimit);
+
+  const std::string nested_mangled_name0 = NestedMangledName(0);
+  demangled = DemangleStackConsumption(nested_mangled_name0.c_str(),
+                                       &stack_consumed);
+  EXPECT_STREQ("a", demangled);
+  EXPECT_GT(stack_consumed, 0);
+  EXPECT_LT(stack_consumed, kStackConsumptionUpperLimit);
+
+  const std::string nested_mangled_name1 = NestedMangledName(1);
+  demangled = DemangleStackConsumption(nested_mangled_name1.c_str(),
+                                       &stack_consumed);
+  EXPECT_STREQ("a<>", demangled);
+  EXPECT_GT(stack_consumed, 0);
+  EXPECT_LT(stack_consumed, kStackConsumptionUpperLimit);
+
+  const std::string nested_mangled_name2 = NestedMangledName(2);
+  demangled = DemangleStackConsumption(nested_mangled_name2.c_str(),
+                                       &stack_consumed);
+  EXPECT_STREQ("a<>", demangled);
+  EXPECT_GT(stack_consumed, 0);
+  EXPECT_LT(stack_consumed, kStackConsumptionUpperLimit);
+
+  const std::string nested_mangled_name3 = NestedMangledName(3);
+  demangled = DemangleStackConsumption(nested_mangled_name3.c_str(),
+                                       &stack_consumed);
+  EXPECT_STREQ("a<>", demangled);
+  EXPECT_GT(stack_consumed, 0);
+  EXPECT_LT(stack_consumed, kStackConsumptionUpperLimit);
+}
+
+#endif  // Stack consumption tests
+
+static void TestOnInput(const char* input) {
+  static const int kOutSize = 1048576;
+  auto out = absl::make_unique<char[]>(kOutSize);
+  Demangle(input, out.get(), kOutSize);
+}
+
+TEST(DemangleRegression, NegativeLength) {
+  TestOnInput("_ZZn4");
+}
+TEST(DemangleRegression, DeeplyNestedArrayType) {
+  const int depth = 100000;
+  std::string data = "_ZStI";
+  data.reserve(data.size() + 3 * depth + 1);
+  for (int i = 0; i < depth; i++) {
+    data += "A1_";
+  }
+  TestOnInput(data.c_str());
+}
+
+}  // namespace
+}  // namespace debugging_internal
+}  // namespace absl