[Reflection] Change ReadBytesFunction to return a pointer rather than copying data, and adjust its users accordingly.

rdar://problem/37538580

include/swift/Remote/CMemoryReader.h

@@ -62,17 +62,27 @@ public:
     if (!length)
       return false;
 
-    auto buffer = std::unique_ptr<uint8_t>(new uint8_t[length + 1]);
-    if (!readBytes(address, buffer.get(), length + 1))
+    const void *ptr;
+    std::function<void()> freeFunc;
+    std::tie(ptr, freeFunc) = readBytes(address, length);
+    if (ptr != nullptr) {
+      dest = std::string(reinterpret_cast<const char *>(ptr), length);
+      freeFunc();
+      return true;
+    } else {
       return false;
-
-    dest = std::string(reinterpret_cast<const char *>(buffer.get()));
-    return true;
+    }
   }
 
-  bool readBytes(RemoteAddress address, uint8_t *dest, uint64_t size) override {
-    return Impl.readBytes(Impl.reader_context,
-                          address.getAddressData(), dest, size) != 0;
+  std::tuple<const void *, std::function<void()>>
+    readBytes(RemoteAddress address, uint64_t size) override {
+      FreeBytesFunction freeFunc;
+      void *freeContext;
+      auto ptr = Impl.readBytes(Impl.reader_context, address.getAddressData(), size,
+                                &freeFunc, &freeContext);
+      auto freeLambda = [=]{ freeFunc(ptr, freeContext); };
+      
+      return std::make_tuple(ptr, freeLambda);
   }
 };
 

include/swift/Remote/InProcessMemoryReader.h

@@ -42,9 +42,9 @@ class InProcessMemoryReader final : public MemoryReader {
     return true;
   }
 
-  bool readBytes(RemoteAddress address, uint8_t *dest, uint64_t size) override {
-    std::memcpy(dest, address.getLocalPointer<void>(), (size_t) size);
-    return true;
+  std::tuple<const void *, std::function<void()>>
+    readBytes(RemoteAddress address, uint64_t size) override {
+    return std::make_tuple(address.getLocalPointer<void>(), []{});
   }
 };
  

include/swift/Remote/MemoryReader.h

@@ -20,7 +20,9 @@
 
 #include "swift/Remote/RemoteAddress.h"
 
+#include <functional>
 #include <string>
+#include <tuple>
 
 namespace swift {
 namespace remote {
@@ -40,12 +42,12 @@ public:
   /// Look up the given public symbol name in the remote process.
   virtual RemoteAddress getSymbolAddress(const std::string &name) = 0;
 
-  /// Attempts to read 'size' bytes from the given address in the
-  /// remote process.
+  /// Attempts to read 'size' bytes from the given address in the remote process.
   ///
-  /// Returns false if the operation failed.
-  virtual bool readBytes(RemoteAddress address, uint8_t *dest,
-                         uint64_t size) = 0;
+  /// Returns a pointer to the requested data and a function that must be called to
+  /// free that data when done. The pointer will be NULL if the operation failed.
+  virtual std::tuple<const void *, std::function<void()>>
+    readBytes(RemoteAddress address, uint64_t size) = 0;
 
   /// Attempts to read a C string from the given address in the remote
   /// process.
@@ -63,6 +65,23 @@ public:
                      sizeof(IntegerType));
   }
 
+  /// Attempts to read 'size' bytes from the given address in the
+  /// remote process.
+  ///
+  /// Returns false if the operation failed.
+  bool readBytes(RemoteAddress address, uint8_t *dest, uint64_t size) {
+    const void *ptr;
+    std::function<void()> freeFunc;
+    std::tie(ptr, freeFunc) = readBytes(address, size);
+    if (ptr != nullptr) {
+      memcpy(dest, ptr, size);
+      freeFunc();
+      return true;
+    } else {
+      return false;
+    }
+  }
+          
   virtual ~MemoryReader() = default;
 };
 

include/swift/SwiftRemoteMirror/MemoryReaderInterface.h

@@ -32,13 +32,14 @@ extern "C" {
 // in the system library, so we use 'swift_addr_t'.
 typedef uint64_t swift_addr_t;
 
-typedef void (*FreeBytesFunction)(void *bytes, void *context);
+typedef void (*FreeBytesFunction)(const void *bytes, void *context);
 
 typedef uint8_t (*PointerSizeFunction)(void *reader_context);
 typedef uint8_t (*SizeSizeFunction)(void *reader_context);
-typedef void *(*ReadBytesFunction)(void *reader_context, swift_addr_t address,
-                                 uint64_t size, FreeBytesFunction *outFreeFunction,
-                                 void **outFreeContext);
+typedef const void *(*ReadBytesFunction)(void *reader_context, swift_addr_t address,
+                                         uint64_t size,
+                                         FreeBytesFunction *outFreeFunction,
+                                         void **outFreeContext);
 typedef uint64_t (*GetStringLengthFunction)(void *reader_context,
                                             swift_addr_t address);
 typedef swift_addr_t (*GetSymbolAddressFunction)(void *reader_context,

tools/swift-reflection-dump/swift-reflection-dump.cpp

@@ -191,15 +191,14 @@ public:
     return false;
   }
   
-  bool readBytes(RemoteAddress address, uint8_t *dest,
-                 uint64_t size) override {
+  std::tuple<const void *, std::function<void()>>
+    readBytes(RemoteAddress address, uint64_t size) override {
     if (!isAddressValid(address, size))
-      return false;
+      return std::make_tuple(nullptr, []{});
 
     // TODO: Account for offset in ELF binaries
-    auto src = (const void *)address.getAddressData();
-    memcpy(dest, (const void*)src, size);
-    return true;
+    auto ptr = (const void *)address.getAddressData();
+    return std::make_tuple(ptr, []{});
   }
   
   bool readString(RemoteAddress address, std::string &dest) override {

tools/swift-reflection-test/swift-reflection-test.c

@@ -95,9 +95,15 @@ void PipeMemoryReader_collectBytesFromPipe(const PipeMemoryReader *Reader,
   }
 }
 
+static void PipeMemoryReader_freeBytes(const void *bytes, void *context) {
+  free((void *)bytes);
+}
+
 static
-int PipeMemoryReader_readBytes(void *Context, swift_addr_t Address, void *Dest,
-                               uint64_t Size) {
+const void *PipeMemoryReader_readBytes(void *Context, swift_addr_t Address,
+                                       uint64_t Size,
+                                       FreeBytesFunction *outFreeFunction,
+                                       void **outFreeContext) {
   const PipeMemoryReader *Reader = (const PipeMemoryReader *)Context;
   uintptr_t TargetAddress = Address;
   size_t TargetSize = (size_t)Size;
@@ -105,8 +111,14 @@ int PipeMemoryReader_readBytes(void *Context, swift_addr_t Address, void *Dest,
   write(WriteFD, REQUEST_READ_BYTES, 2);
   write(WriteFD, &TargetAddress, sizeof(TargetAddress));
   write(WriteFD, &TargetSize, sizeof(size_t));
-  PipeMemoryReader_collectBytesFromPipe(Reader, Dest, Size);
-  return 1;
+  
+  void *Buf = malloc(Size);
+  PipeMemoryReader_collectBytesFromPipe(Reader, Buf, Size);
+  
+  *outFreeFunction = PipeMemoryReader_freeBytes;
+  *outFreeContext = NULL;
+  
+  return Buf;
 }
 
 static