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diff --git a/absl/debugging/internal/demangle_test.cc b/absl/debugging/internal/demangle_test.cc
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+++ b/absl/debugging/internal/demangle_test.cc
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+// 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