[clang] Use -Wshorten-64-to-32 to enable warnings about 64bit to 32bit truncations.

src/snapshot/mksnapshot.cc

Index: src/snapshot/mksnapshot.cc
diff --git a/src/snapshot/mksnapshot.cc b/src/snapshot/mksnapshot.cc
index 79c1643fb810ed6d7f3eda64942b6d475ad93d33..f44eca523a8d3e0660ca332ce1aa3dc73599b626 100644
--- a/src/snapshot/mksnapshot.cc
+++ b/src/snapshot/mksnapshot.cc
@@ -118,13 +118,13 @@ char* GetExtraCode(char* filename) {
     exit(1);
   }
   fseek(file, 0, SEEK_END);
-  int size = ftell(file);
+  size_t size = ftell(file);
   rewind(file);
   char* chars = new char[size + 1];
   chars[size] = '\0';
-  for (int i = 0; i < size;) {
-    int read = static_cast<int>(fread(&chars[i], 1, size - i, file));
-    if (read < 0) {
+  for (size_t i = 0; i < size;) {
+    size_t read = fread(&chars[i], 1, size - i, file);
+    if (ferror(file)) {
       fprintf(stderr, "Failed to read '%s': errno %d\n", filename, errno);
       exit(1);
     }