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

runtime/bin/dartutils.cc

Index: runtime/bin/dartutils.cc
diff --git a/runtime/bin/dartutils.cc b/runtime/bin/dartutils.cc
index a90694d8733b4dd010cba34fa359402940967b9b..a2fdf9d41eaa02300ea89395139c32191a8342dd 100644
--- a/runtime/bin/dartutils.cc
+++ b/runtime/bin/dartutils.cc
@@ -364,12 +364,12 @@ Dart_Handle DartUtils::ReadStringFromHttp(const char* script_uri) {
 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) {