- ed0ba496fe01eb8edfa86beade8a37768e7c12ef Updates the API for Exception Safety testing to use build... by Abseil Team <absl-team@google.com>

  - c4b7a4e517c9404932c45f2f9f92eb7dc694e45d Internal change by Abseil Team <absl-team@google.com>
  - 76c78ed9385f65d881511645446e0bb8ababf6ec Add missing ABSL_PREDICT_FALSE to one of FixedArray::at()... by Abseil Team <absl-team@google.com>
  - 1204fb1c46f007dd9dfb7d9abf3e96c58835d193 Internal change. by Greg Falcon <gfalcon@google.com>
  - f1f47c98a026bc5e425ae83ff4a2eb391bbd3d9b Add internal-only functionality to examine the stack, to ... by Derek Mauro <dmauro@google.com>
  - 30d63097cd268d912f917526f6511005580465c4 fix typo by Abseil Team <absl-team@google.com>
  - 942d7efa6cf54cd248ca57dcaf3c245188b52a76 Remove unnecessary semicolons from comment examples. by Abseil Team <absl-team@google.com>
  - 7db0669cf23a06d934d3ed8c76aee4e4e23b7e04 Remove malloc_hook and malloc_extension from our internal... by Greg Falcon <gfalcon@google.com>
  - 0190f1063d101b1ded355019df2e1d325931f6c7 Make the maximum length of a string view equal difference... by Abseil Team <absl-team@google.com>
  - c8ae37cbce29449b02115a0ebd435ddc3d7ab062 Add namespace qualification. by Shaindel Schwartz <shaindel@google.com>
  - ff70afe2e6e3dd39f51ce9829e3e1f18231bf4d7 Fix internal/direct_mmap.h for non-linux builds. by Greg Falcon <gfalcon@google.com>

GitOrigin-RevId: ed0ba496fe01eb8edfa86beade8a37768e7c12ef
Change-Id: I7595ee3480d1d6724fd3797c15ba9d9be0d17e62

4 files changed, 222 insertions, 1 deletions

diff --git a/absl/debugging/BUILD.bazel b/absl/debugging/BUILD.bazel
index f6859093ddc7..8543200df87d 100644
--- a/absl/debugging/BUILD.bazel
+++ b/absl/debugging/BUILD.bazel
@@ -76,6 +76,24 @@ cc_test(
 )
 
 cc_library(
+    name = "examine_stack",
+    srcs = [
+        "internal/examine_stack.cc",
+    ],
+    hdrs = [
+        "internal/examine_stack.h",
+    ],
+    copts = ABSL_DEFAULT_COPTS,
+    visibility = ["//visibility:private"],
+    deps = [
+        ":stacktrace",
+        ":symbolize",
+        "//absl/base",
+        "//absl/base:core_headers",
+    ],
+)
+
+cc_library(
     name = "debugging_internal",
     srcs = [
         "internal/address_is_readable.cc",
@@ -234,11 +252,11 @@ cc_library(
     srcs = ["internal/stack_consumption.cc"],
     hdrs = ["internal/stack_consumption.h"],
     copts = ABSL_DEFAULT_COPTS,
+    visibility = ["//visibility:private"],
     deps = [
         "//absl/base",
         "//absl/base:core_headers",
     ],
-    visibility = ["//visibility:private"],
 )
 
 cc_test(
diff --git a/absl/debugging/CMakeLists.txt b/absl/debugging/CMakeLists.txt
index b9aec5fa63dc..8d2ec845d67b 100644
--- a/absl/debugging/CMakeLists.txt
+++ b/absl/debugging/CMakeLists.txt
@@ -25,6 +25,7 @@ list(APPEND DEBUGGING_INTERNAL_HEADERS
   "internal/address_is_readable.h"
   "internal/demangle.h"
   "internal/elf_mem_image.h"
+  "internal/examine_stack.h"
   "internal/stacktrace_config.h"
   "internal/symbolize.h"
   "internal/vdso_support.h"
@@ -49,6 +50,12 @@ list(APPEND SYMBOLIZE_SRC
   ${DEBUGGING_INTERNAL_HEADERS}
 )
 
+list(APPEND EXAMINE_STACK_SRC
+  "internal/examine_stack.cc"
+  ${DEBUGGING_PUBLIC_HEADERS}
+  ${DEBUGGING_INTERNAL_HEADERS}
+)
+
 absl_library(
   TARGET
     absl_stacktrace
@@ -67,6 +74,17 @@ absl_library(
     symbolize
 )
 
+# Internal-only. Projects external to Abseil should not depend
+# directly on this library.
+absl_library(
+  TARGET
+    absl_examine_stack
+  SOURCES
+    ${EXAMINE_STACK_SRC}
+  EXPORT_NAME
+    examine_stack
+)
+
 list(APPEND LEAK_CHECK_SRC
   "leak_check.cc"
 )
diff --git a/absl/debugging/internal/examine_stack.cc b/absl/debugging/internal/examine_stack.cc
new file mode 100644
index 000000000000..261daae932f1
--- /dev/null
+++ b/absl/debugging/internal/examine_stack.cc
@@ -0,0 +1,147 @@
+//
+// 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/examine_stack.h"
+
+#ifndef _WIN32
+#include <unistd.h>
+#endif
+
+#include <csignal>
+#include <cstdio>
+
+#include "absl/base/attributes.h"
+#include "absl/base/internal/raw_logging.h"
+#include "absl/base/macros.h"
+#include "absl/debugging/stacktrace.h"
+#include "absl/debugging/symbolize.h"
+
+namespace absl {
+namespace debugging_internal {
+
+// Returns the program counter from signal context, nullptr if
+// unknown. vuc is a ucontext_t*. We use void* to avoid the use of
+// ucontext_t on non-POSIX systems.
+void* GetProgramCounter(void* vuc) {
+#ifdef __linux__
+  if (vuc != nullptr) {
+    ucontext_t* context = reinterpret_cast<ucontext_t*>(vuc);
+#if defined(__aarch64__)
+    return reinterpret_cast<void*>(context->uc_mcontext.pc);
+#elif defined(__arm__)
+    return reinterpret_cast<void*>(context->uc_mcontext.arm_pc);
+#elif defined(__i386__)
+    if (14 < ABSL_ARRAYSIZE(context->uc_mcontext.gregs))
+      return reinterpret_cast<void*>(context->uc_mcontext.gregs[14]);
+#elif defined(__powerpc64__)
+    return reinterpret_cast<void*>(context->uc_mcontext.gp_regs[32]);
+#elif defined(__powerpc__)
+    return reinterpret_cast<void*>(context->uc_mcontext.regs->nip);
+#elif defined(__x86_64__)
+    if (16 < ABSL_ARRAYSIZE(context->uc_mcontext.gregs))
+      return reinterpret_cast<void*>(context->uc_mcontext.gregs[16]);
+#else
+#error "Undefined Architecture."
+#endif
+  }
+#elif defined(__akaros__)
+  auto* ctx = reinterpret_cast<struct user_context*>(vuc);
+  return reinterpret_cast<void*>(get_user_ctx_pc(ctx));
+#endif
+  static_cast<void>(vuc);
+  return nullptr;
+}
+
+// The %p field width for printf() functions is two characters per byte,
+// and two extra for the leading "0x".
+static constexpr int kPrintfPointerFieldWidth = 2 + 2 * sizeof(void*);
+
+// Print a program counter, its stack frame size, and its symbol name.
+// Note that there is a separate symbolize_pc argument. Return addresses may be
+// at the end of the function, and this allows the caller to back up from pc if
+// appropriate.
+static void DumpPCAndFrameSizeAndSymbol(void (*writerfn)(const char*, void*),
+                                        void* writerfn_arg, void* pc,
+                                        void* symbolize_pc, int framesize,
+                                        const char* const prefix) {
+  char tmp[1024];
+  const char* symbol = "(unknown)";
+  if (absl::Symbolize(symbolize_pc, tmp, sizeof(tmp))) {
+    symbol = tmp;
+  }
+  char buf[1024];
+  if (framesize <= 0) {
+    snprintf(buf, sizeof(buf), "%s@ %*p  (unknown)  %s\n", prefix,
+             kPrintfPointerFieldWidth, pc, symbol);
+  } else {
+    snprintf(buf, sizeof(buf), "%s@ %*p  %9d  %s\n", prefix,
+             kPrintfPointerFieldWidth, pc, framesize, symbol);
+  }
+  writerfn(buf, writerfn_arg);
+}
+
+// Print a program counter and the corresponding stack frame size.
+static void DumpPCAndFrameSize(void (*writerfn)(const char*, void*),
+                               void* writerfn_arg, void* pc, int framesize,
+                               const char* const prefix) {
+  char buf[100];
+  if (framesize <= 0) {
+    snprintf(buf, sizeof(buf), "%s@ %*p  (unknown)\n", prefix,
+             kPrintfPointerFieldWidth, pc);
+  } else {
+    snprintf(buf, sizeof(buf), "%s@ %*p  %9d\n", prefix,
+             kPrintfPointerFieldWidth, pc, framesize);
+  }
+  writerfn(buf, writerfn_arg);
+}
+
+void DumpPCAndFrameSizesAndStackTrace(
+    void* pc, void* const stack[], int frame_sizes[], int depth,
+    int min_dropped_frames, bool symbolize_stacktrace,
+    void (*writerfn)(const char*, void*), void* writerfn_arg) {
+  if (pc != nullptr) {
+    // We don't know the stack frame size for PC, use 0.
+    if (symbolize_stacktrace) {
+      DumpPCAndFrameSizeAndSymbol(writerfn, writerfn_arg, pc, pc, 0, "PC: ");
+    } else {
+      DumpPCAndFrameSize(writerfn, writerfn_arg, pc, 0, "PC: ");
+    }
+  }
+  for (int i = 0; i < depth; i++) {
+    if (symbolize_stacktrace) {
+      // Pass the previous address of pc as the symbol address because pc is a
+      // return address, and an overrun may occur when the function ends with a
+      // call to a function annotated noreturn (e.g. CHECK). Note that we don't
+      // do this for pc above, as the adjustment is only correct for return
+      // addresses.
+      DumpPCAndFrameSizeAndSymbol(writerfn, writerfn_arg, stack[i],
+                                  reinterpret_cast<char*>(stack[i]) - 1,
+                                  frame_sizes[i], "    ");
+    } else {
+      DumpPCAndFrameSize(writerfn, writerfn_arg, stack[i], frame_sizes[i],
+                         "    ");
+    }
+  }
+  if (min_dropped_frames > 0) {
+    char buf[100];
+    snprintf(buf, sizeof(buf), "    @ ... and at least %d more frames\n",
+             min_dropped_frames);
+    writerfn(buf, writerfn_arg);
+  }
+}
+
+}  // namespace debugging_internal
+}  // namespace absl
diff --git a/absl/debugging/internal/examine_stack.h b/absl/debugging/internal/examine_stack.h
new file mode 100644
index 000000000000..a16c03b2748f
--- /dev/null
+++ b/absl/debugging/internal/examine_stack.h
@@ -0,0 +1,38 @@
+//
+// 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.
+//
+
+#ifndef ABSL_DEBUGGING_INTERNAL_EXAMINE_STACK_H_
+#define ABSL_DEBUGGING_INTERNAL_EXAMINE_STACK_H_
+
+namespace absl {
+namespace debugging_internal {
+
+// Returns the program counter from signal context, or nullptr if
+// unknown. `vuc` is a ucontext_t*. We use void* to avoid the use of
+// ucontext_t on non-POSIX systems.
+void* GetProgramCounter(void* vuc);
+
+// Uses `writerfn` to dump the program counter, stack trace, and stack
+// frame sizes.
+void DumpPCAndFrameSizesAndStackTrace(
+    void* pc, void* const stack[], int frame_sizes[], int depth,
+    int min_dropped_frames, bool symbolize_stacktrace,
+    void (*writerfn)(const char*, void*), void* writerfn_arg);
+
+}  // namespace debugging_internal
+}  // namespace absl
+
+#endif  // ABSL_DEBUGGING_INTERNAL_EXAMINE_STACK_H_