Rewrite libbacktrace using C++.

The old code was essentially trying to be C++ in C and was awkward. This
change makes it all objects with a thin layer that C code can use.

There is a C++ backtrace object that is not very useful, this code will
replace it.

This change also includes moving the backtrace test to a gtest, and adding
coverage of all major functionality.

Bug: 8410085
Change-Id: Iae0f1b09b3dd60395f71ed66010c1ea5cdd37841

2 files changed, 120 insertions, 25 deletions

diff --git a/include/backtrace/Backtrace.h b/include/backtrace/Backtrace.h
new file mode 100644
index 0000000..0b75e83
--- /dev/null
+++ b/include/backtrace/Backtrace.h
@@ -0,0 +1,85 @@
+/*
+ * Copyright (C) 2013 The Android Open Source Project
+ *
+ * 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 _BACKTRACE_BACKTRACE_H
+#define _BACKTRACE_BACKTRACE_H
+
+#include <backtrace/backtrace.h>
+
+#include <string>
+
+class BacktraceImpl;
+
+class Backtrace {
+public:
+  Backtrace(BacktraceImpl* impl);
+  virtual ~Backtrace();
+
+  // Get the current stack trace and store in the backtrace_ structure.
+  virtual bool Unwind(size_t num_ignore_frames);
+
+  // Get the function name and offset into the function given the pc.
+  // If the string is empty, then no valid function name was found.
+  virtual std::string GetFunctionName(uintptr_t pc, uintptr_t* offset);
+
+  // Get the name of the map associated with the given pc. If NULL is returned,
+  // then map_start is not set. Otherwise, map_start is the beginning of this
+  // map.
+  virtual const char* GetMapName(uintptr_t pc, uintptr_t* map_start);
+
+  // Finds the memory map associated with the given ptr.
+  virtual const backtrace_map_info_t* FindMapInfo(uintptr_t ptr);
+
+  // Read the data at a specific address.
+  virtual bool ReadWord(uintptr_t ptr, uint32_t* out_value) = 0;
+
+  // Create a string representing the formatted line of backtrace information
+  // for a single frame.
+  virtual std::string FormatFrameData(size_t frame_num);
+
+  pid_t Pid() { return backtrace_.pid; }
+  pid_t Tid() { return backtrace_.tid; }
+  size_t NumFrames() { return backtrace_.num_frames; }
+
+  const backtrace_t* GetBacktrace() { return &backtrace_; }
+
+  const backtrace_frame_data_t* GetFrame(size_t frame_num) {
+    return &backtrace_.frames[frame_num];
+  }
+
+  // Create the correct Backtrace object based on what is to be unwound.
+  // If pid < 0 or equals the current pid, then the Backtrace object
+  // corresponds to the current process.
+  // If pid < 0 or equals the current pid and tid >= 0, then the Backtrace
+  // object corresponds to a thread in the current process.
+  // If pid >= 0 and tid < 0, then the Backtrace object corresponds to a
+  // different process.
+  // Tracing a thread in a different process is not supported.
+  static Backtrace* Create(pid_t pid, pid_t tid);
+
+protected:
+  virtual bool VerifyReadWordArgs(uintptr_t ptr, uint32_t* out_value);
+
+  BacktraceImpl* impl_;
+
+  backtrace_map_info_t* map_info_;
+
+  backtrace_t backtrace_;
+
+  friend class BacktraceImpl;
+};
+
+#endif // _BACKTRACE_BACKTRACE_H
diff --git a/include/backtrace/backtrace.h b/include/backtrace/backtrace.h
index b6bff38..b35a6d5 100644
--- a/include/backtrace/backtrace.h
+++ b/include/backtrace/backtrace.h
@@ -21,9 +21,7 @@
 #include <stdbool.h>
 #include <inttypes.h>
 
-#ifdef __cplusplus
-extern "C" {
-#endif
+__BEGIN_DECLS
 
 #define MAX_BACKTRACE_FRAMES 64
 
@@ -43,48 +41,58 @@ typedef struct {
   size_t stack_size;      /* The size of the stack, zero indicate an unknown stack size. */
   const char* map_name;   /* The name of the map to which this pc belongs, NULL indicates the pc doesn't belong to a known map. */
   uintptr_t map_offset;   /* pc relative to the start of the map, only valid if map_name is not NULL. */
-  char* proc_name;        /* The function name associated with this pc, NULL if not found. */
-  uintptr_t proc_offset;  /* pc relative to the start of the procedure, only valid if proc_name is not NULL. */
+  char* func_name;        /* The function name associated with this pc, NULL if not found. */
+  uintptr_t func_offset;  /* pc relative to the start of the function, only valid if func_name is not NULL. */
 } backtrace_frame_data_t;
 
 typedef struct {
   backtrace_frame_data_t frames[MAX_BACKTRACE_FRAMES];
   size_t num_frames;
 
+  pid_t pid;
   pid_t tid;
   backtrace_map_info_t* map_info_list;
-  void* private_data;
 } backtrace_t;
 
-/* Gather the backtrace data for tid and fill in the backtrace structure.
- * If tid < 0, then gather the backtrace for the current thread.
+typedef struct {
+  void* data;
+  const backtrace_t* backtrace;
+} backtrace_context_t;
+
+/* Create a context for the backtrace data and gather the backtrace.
+ * If pid < 0, then gather the backtrace for the current process.
  */
-bool backtrace_get_data(backtrace_t* backtrace, pid_t tid);
+bool backtrace_create_context(
+    backtrace_context_t* context, pid_t pid, pid_t tid, size_t num_ignore_frames);
 
-/* Free any memory associated with the backtrace structure. */
-void backtrace_free_data(backtrace_t* backtrace);
+/* Gather the backtrace data for a pthread instead of a process. */
+bool backtrace_create_thread_context(
+    backtrace_context_t* context, pid_t tid, size_t num_ignore_frames);
+
+/* Free any memory allocated during the context create. */
+void backtrace_destroy_context(backtrace_context_t* context);
 
 /* Read data at a specific address for a process. */
 bool backtrace_read_word(
-    const backtrace_t* backtrace, uintptr_t ptr, uint32_t* value);
+    const backtrace_context_t* context, uintptr_t ptr, uint32_t* value);
 
-/* Get information about the map associated with a pc. If NULL is
+/* Get information about the map name associated with a pc. If NULL is
  * returned, then map_start is not set.
  */
-const char* backtrace_get_map_info(
-    const backtrace_t* backtrace, uintptr_t pc, uintptr_t* map_start);
+const char* backtrace_get_map_name(
+    const backtrace_context_t* context, uintptr_t pc, uintptr_t* map_start);
 
-/* Get the procedure name and offest given the pc. If NULL is returned,
- * then proc_offset is not set. The returned string is allocated using
+/* Get the function name and offset given the pc. If NULL is returned,
+ * then func_offset is not set. The returned string is allocated using
  * malloc and must be freed by the caller.
  */
-char* backtrace_get_proc_name(
-    const backtrace_t* backtrace, uintptr_t pc, uintptr_t* proc_offset);
+char* backtrace_get_func_name(
+    const backtrace_context_t* context, uintptr_t pc, uintptr_t* func_offset);
 
-/* Loads memory map from /proc/<tid>/maps. If tid < 0, then load the memory
+/* Loads memory map from /proc/<pid>/maps. If pid < 0, then load the memory
  * map for the current process.
  */
-backtrace_map_info_t* backtrace_create_map_info_list(pid_t tid);
+backtrace_map_info_t* backtrace_create_map_info_list(pid_t pid);
 
 /* Frees memory associated with the map list. */
 void backtrace_destroy_map_info_list(backtrace_map_info_t* map_info_list);
@@ -95,10 +103,12 @@ const backtrace_map_info_t* backtrace_find_map_info(
 
 /* Create a formatted line of backtrace information for a single frame. */
 void backtrace_format_frame_data(
-    const backtrace_frame_data_t* frame, size_t frame_num, char *buf, size_t buf_size);
+    const backtrace_context_t* context, size_t frame_num, char* buf,
+    size_t buf_size);
+
+/* Get the backtrace data structure associated with the context. */
+const backtrace_t* backtrace_get_data(backtrace_context_t* context);
 
-#ifdef __cplusplus
-}
-#endif
+__END_DECLS
 
 #endif /* _BACKTRACE_H */