1 files changed, 99 insertions, 3 deletions

diff --git a/libutils/include/utils/CallStack.h b/libutils/include/utils/CallStack.h
index 0c1b87522..56004fe49 100644
--- a/libutils/include/utils/CallStack.h
+++ b/libutils/include/utils/CallStack.h
@@ -17,6 +17,8 @@
 #ifndef ANDROID_CALLSTACK_H
 #define ANDROID_CALLSTACK_H
 
+#include <memory>
+
 #include <android/log.h>
 #include <backtrace/backtrace_constants.h>
 #include <utils/String8.h>
@@ -25,6 +27,19 @@
 #include <stdint.h>
 #include <sys/types.h>
 
+#if !defined(__APPLE__) && !defined(_WIN32)
+# define WEAKS_AVAILABLE 1
+#endif
+#ifndef CALLSTACK_WEAK
+# ifdef WEAKS_AVAILABLE
+#   define CALLSTACK_WEAK __attribute__((weak))
+# else // !WEAKS_AVAILABLE
+#   define CALLSTACK_WEAK
+# endif // !WEAKS_AVAILABLE
+#endif // CALLSTACK_WEAK predefined
+
+#define ALWAYS_INLINE __attribute__((always_inline))
+
 namespace android {
 
 class Printer;
@@ -36,7 +51,7 @@ public:
     CallStack();
     // Create a callstack with the current thread's stack trace.
     // Immediately dump it to logcat using the given logtag.
-    CallStack(const char* logtag, int32_t ignoreDepth=1);
+    CallStack(const char* logtag, int32_t ignoreDepth = 1);
     ~CallStack();
 
     // Reset the stack frames (same as creating an empty call stack).
@@ -44,7 +59,7 @@ public:
 
     // Immediately collect the stack traces for the specified thread.
     // The default is to dump the stack of the current call.
-    void update(int32_t ignoreDepth=1, pid_t tid=BACKTRACE_CURRENT_THREAD);
+    void update(int32_t ignoreDepth = 1, pid_t tid = BACKTRACE_CURRENT_THREAD);
 
     // Dump a stack trace to the log using the supplied logtag.
     void log(const char* logtag,
@@ -63,7 +78,88 @@ public:
     // Get the count of stack frames that are in this call stack.
     size_t size() const { return mFrameLines.size(); }
 
-private:
+    // DO NOT USE ANYTHING BELOW HERE. The following public members are expected
+    // to disappear again shortly, once a better replacement facility exists.
+    // The replacement facility will be incompatible!
+
+    // Debugging accesses to some basic functionality. These use weak symbols to
+    // avoid introducing a dependency on libutilscallstack. Such a dependency from
+    // libutils results in a cyclic build dependency. These routines can be called
+    // from within libutils. But if the actual library is unavailable, they do
+    // nothing.
+    //
+    // DO NOT USE THESE. They will disappear.
+    struct StackDeleter {
+#ifdef WEAKS_AVAILABLE
+        void operator()(CallStack* stack) {
+            deleteStack(stack);
+        }
+#else
+        void operator()(CallStack*) {}
+#endif
+    };
+
+    typedef std::unique_ptr<CallStack, StackDeleter> CallStackUPtr;
+
+    // Return current call stack if possible, nullptr otherwise.
+#ifdef WEAKS_AVAILABLE
+    static CallStackUPtr ALWAYS_INLINE getCurrent(int32_t ignoreDepth = 1) {
+        if (reinterpret_cast<uintptr_t>(getCurrentInternal) == 0) {
+            ALOGW("CallStack::getCurrentInternal not linked, returning null");
+            return CallStackUPtr(nullptr);
+        } else {
+            return getCurrentInternal(ignoreDepth);
+        }
+    }
+#else // !WEAKS_AVAILABLE
+    static CallStackUPtr ALWAYS_INLINE getCurrent(int32_t = 1) {
+        return CallStackUPtr(nullptr);
+    }
+#endif // !WEAKS_AVAILABLE
+
+#ifdef WEAKS_AVAILABLE
+    static void ALWAYS_INLINE logStack(const char* logtag, CallStack* stack = getCurrent().get(),
+                                       android_LogPriority priority = ANDROID_LOG_DEBUG) {
+        if (reinterpret_cast<uintptr_t>(logStackInternal) != 0 && stack != nullptr) {
+            logStackInternal(logtag, stack, priority);
+        } else {
+            ALOGW("CallStack::logStackInternal not linked");
+        }
+    }
+
+#else
+    static void ALWAYS_INLINE logStack(const char*, CallStack* = getCurrent().get(),
+                                       android_LogPriority = ANDROID_LOG_DEBUG) {
+    }
+#endif // !WEAKS_AVAILABLE
+
+#ifdef WEAKS_AVAILABLE
+    static String8 ALWAYS_INLINE stackToString(const char* prefix = nullptr,
+                                               const CallStack* stack = getCurrent().get()) {
+        if (reinterpret_cast<uintptr_t>(stackToStringInternal) != 0 && stack != nullptr) {
+            return stackToStringInternal(prefix, stack);
+        } else {
+            return String8("<CallStack package not linked>");
+        }
+    }
+#else // !WEAKS_AVAILABLE
+    static String8 ALWAYS_INLINE stackToString(const char* = nullptr,
+                                               const CallStack* = getCurrent().get()) {
+        return String8("<CallStack package not linked>");
+    }
+#endif // !WEAKS_AVAILABLE
+
+  private:
+#ifdef WEAKS_AVAILABLE
+    static CallStackUPtr CALLSTACK_WEAK getCurrentInternal(int32_t ignoreDepth);
+    static void CALLSTACK_WEAK logStackInternal(const char* logtag, const CallStack* stack,
+                                                android_LogPriority priority);
+    static String8 CALLSTACK_WEAK stackToStringInternal(const char* prefix, const CallStack* stack);
+    // The deleter is only invoked on non-null pointers. Hence it will never be
+    // invoked if CallStack is not linked.
+    static void CALLSTACK_WEAK deleteStack(CallStack* stack);
+#endif // WEAKS_AVAILABLE
+
     Vector<String8> mFrameLines;
 };