Fixes to get Dart VM compiling on Ubuntu 13.04, Debian Wheezy.

runtime/bin/dartutils.cc

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "bin/dartutils.h"
 
 #include "include/dart_api.h"
 #include "include/dart_native_api.h"
 
 #include "platform/assert.h"
@@ skipping 346 matching lines @@
   Dart_Handle str = Dart_NewStringFromUTF8(buffer,
                                            bufferLen);
   free(buffer);
   return str;
 }
 
 
 static const uint8_t* ReadFileFully(const char* filename,
                                     intptr_t* file_len,
                                     const char** error_msg) {
+  *file_len = -1;
   void* stream = DartUtils::OpenFile(filename, false);
   if (stream == NULL) {
     SET_ERROR_MSG(error_msg, "Unable to open file: %s", filename);
     return NULL;
   }
-  *file_len = -1;
   const uint8_t* text_buffer = NULL;

[siva, 2013/08/06 22:53:43]

Not sure I understand why *file_len = 1 needs to be moved up.
It is not used in the chunk of code above....

[Chris Bracken, 2013/08/07 06:12:57]

ReadStringFromFile() and LoadScript() both call this function with an
uninitialized stack-allocated local as the out-param file_len, then subsequently
pass that local as a param to another function. In cases where OpenFile()
returns NULL, file_len is left uninitialized. As a result, the compiler issues
an error against the two callers above:

error: ‘len’ may be used uninitialized in this function
[-Werror=maybe-uninitialized]

Both of the callers above actually check the return value of this function for
NULL and bail out before ever using len, but the compiler doesn't see that the
combination of the two result in no cases where len is used uninitialized in our
code, hence the error.

An alternative solution would be to initialize the local len vars in both
callers and leave this code as it was.

   DartUtils::ReadFile(&text_buffer, file_len, stream);
   if (text_buffer == NULL || *file_len == -1) {
     *error_msg = "Unable to read file contents";
     text_buffer = NULL;
   }
   DartUtils::CloseFile(stream);
   return text_buffer;
 }
 
 
@@ skipping 619 matching lines @@
       new CObjectString(CObject::NewString(os_error->message()));
   CObjectArray* result = new CObjectArray(CObject::NewArray(3));
   result->SetAt(0, new CObjectInt32(CObject::NewInt32(kOSError)));
   result->SetAt(1, new CObjectInt32(CObject::NewInt32(os_error->code())));
   result->SetAt(2, error_message);
   return result;
 }
 
 }  // namespace bin
 }  // namespace dart