More completely fixed the 0-key thing.

Unfortunately this degrades hash table lookup performance by
about 8%, which affects the streaming benchmark for googlemessage1
by about 5%.  We could get this back at the cost of some memory,
but it would be nice to avoid that.

Makefile

@@ -40,7 +40,7 @@ LDLIBS=-lpthread src/libupb.a
 # of the scheme we use that compiles the same source file multiple times with
 # different -D options, which can include different header files.
 deps: gen-deps.sh Makefile $(CORE) $(STREAM)
-	@CPPFLAGS="$(CPPFLAGS)" ./gen-deps.sh $(CORE) $(STREAM)
+	@CPPFLAGS="$(CPPFLAGS)" ./gen-deps.sh $(CORE) $(STREAM) $(TOOLS)
 	@echo Regenerating dependencies for src/...
 
 $(ALLSRC): perf-cppflags
@@ -68,6 +68,9 @@ STREAM= \
   src/upb_msg.c \
   src/upb_glue.c \
 
+TOOLS= \
+  src/upbc.c
+
 # Parts of core that are yet to be converted.
 OTHERSRC=src/upb_encoder.c src/upb_text.c
 
@@ -222,13 +225,13 @@ tests/t.test_vs_proto2.googlemessage2: \
 tests/test_table: tests/test_table.cc
 	@# Includes <hash_set> which is a deprecated header.
 	@echo CXX $<
-	$(CXX) $(CXXFLAGS) $(CPPFLAGS) -Wno-deprecated -o $@ $< $(LIBUPB)
+	@$(CXX) $(CXXFLAGS) $(CPPFLAGS) -Wno-deprecated -o $@ $< $(LIBUPB)
 
 tests/tests: src/libupb.a
 
 # Tools
 tools: src/upbc
-tools/upbc: $(LIBUPB)
+src/upbc: $(LIBUPB)
 
 # Benchmarks. ##################################################################
 

src/upb_def.c

@@ -476,12 +476,6 @@ static upb_flow_t upb_enumdef_EnumValueDescriptorProto_value(void *_b,
       break;
     case GOOGLE_PROTOBUF_ENUMVALUEDESCRIPTORPROTO_NUMBER_FIELDNUM:
       b->number = upb_value_getint32(val);
-      if (b->number == 0) {
-        upb_seterr(&b->status, UPB_ERROR,
-                   "Enums with a value of 0 are currently broken; see "
-                   "http://code.google.com/p/upb/issues/detail?id=1.");
-        return UPB_BREAK;
-      }
       b->saw_number = true;
       break;
     default:

src/upb_table.c

@@ -129,7 +129,6 @@ static void intinsert(upb_inttable *t, upb_inttable_entry *e)
 
 void upb_inttable_insert(upb_inttable *t, upb_inttable_entry *e)
 {
-  assert(e->key != 0);
   if((double)(t->t.count + 1) / upb_inttable_size(t) > MAX_LOAD) {
     /* Need to resize.  New table of double the size, add old elements to it. */
     upb_inttable new_table;

src/upb_table.h

@@ -100,12 +100,11 @@ INLINE uint32_t upb_inttable_bucket(upb_inttable *t, upb_inttable_key_t k) {
  * ability to optimize. */
 INLINE void *upb_inttable_fastlookup(upb_inttable *t, uint32_t key,
                                      uint32_t entry_size) {
-  assert(key != 0);
   uint32_t bucket = upb_inttable_bucket(t, key);
   upb_inttable_entry *e;
   do {
     e = (upb_inttable_entry*)UPB_INDEX(t->t.entries, bucket-1, entry_size);
-    if(e->key == key) return e;
+    if(e->key == key && e->has_entry) return e;
   } while((bucket = e->next) != UPB_END_OF_CHAIN);
   return NULL;  /* Not found. */
 }

src/upbc.c

@@ -231,6 +231,7 @@ int main(int argc, char *argv[])
   free(defs);
   upb_string_unref(descriptor);
   upb_symtab_unref(s);
+  upb_symtab_unref(s2);
   fclose(h_const_file);
 
   return 0;