A few more thread-safety fixes.

src/upb_array.h

@@ -55,7 +55,7 @@ INLINE void upb_array_uninit(struct upb_array *arr)
   if(arr->size) free(arr->elements._void);
 }
 
-INLINE struct upb_array *upb_array_new() {
+INLINE struct upb_array *upb_array_new(void) {
   struct upb_array *arr = malloc(sizeof(*arr));
   upb_array_init(arr);
   return arr;

src/upb_context.c

@@ -82,13 +82,24 @@ void upb_context_unref(struct upb_context *c)
   upb_rwlock_destroy(&c->lock);
 }
 
-struct upb_symtab_entry *upb_context_lookup(struct upb_context *c,
-                                            struct upb_string *symbol)
+bool upb_context_lookup(struct upb_context *c, struct upb_string *symbol,
+                        struct upb_symtab_entry *out_entry)
 {
   upb_rwlock_rdlock(&c->lock);
   struct upb_symtab_entry *e = upb_strtable_lookup(&c->symtab, symbol);
+  if(e) *out_entry = *e;
+  upb_rwlock_unlock(&c->lock);
+  return e != NULL;
+}
+
+void upb_context_enumerate(struct upb_context *c, upb_context_enumerator_t cb,
+                           void *udata)
+{
+  upb_rwlock_rdlock(&c->lock);
+  struct upb_symtab_entry *e = upb_strtable_begin(&c->symtab);
+  for(; e; e = upb_strtable_next(&c->symtab, &e->e))
+    cb(udata, e);
   upb_rwlock_unlock(&c->lock);
-  return e;
 }
 
 /* Given a symbol and the base symbol inside which it is defined, find the
@@ -139,13 +150,14 @@ union upb_symbol_ref resolve2(struct upb_strtable *t1, struct upb_strtable *t2,
 }
 
 
-struct upb_symtab_entry *upb_context_resolve(struct upb_context *c,
-                                             struct upb_string *base,
-                                             struct upb_string *symbol) {
+bool upb_context_resolve(struct upb_context *c, struct upb_string *base,
+                         struct upb_string *symbol,
+                         struct upb_symtab_entry *out_entry) {
   upb_rwlock_rdlock(&c->lock);
   struct upb_symtab_entry *e = resolve(&c->symtab, base, symbol);
+  if(e) *out_entry = *e;
   upb_rwlock_unlock(&c->lock);
-  return e;
+  return e != NULL;
 }
 
 /* Joins strings together, for example:

src/upb_context.h

@@ -53,7 +53,7 @@ struct upb_context {
 
 /* Initializes a upb_context.  Contexts are not freed explicitly, but unref'd
  * when the caller is done with them. */
-struct upb_context *upb_context_new();
+struct upb_context *upb_context_new(void);
 INLINE void upb_context_ref(struct upb_context *c) {
   upb_atomic_ref(&c->refcount);
 }
@@ -70,23 +70,24 @@ void upb_context_unref(struct upb_context *c);
  *    root namespace).
  *
  * Returns NULL if the symbol has not been defined. */
-struct upb_symtab_entry *upb_context_resolve(struct upb_context *c,
-                                             struct upb_string *base,
-                                             struct upb_string *symbol);
+bool upb_context_resolve(struct upb_context *c, struct upb_string *base,
+                         struct upb_string *symbol,
+                         struct upb_symtab_entry *out_entry);
 
 /* Find an entry in the symbol table with this exact name.  Returns NULL if no
  * such symbol name exists. */
-struct upb_symtab_entry *upb_context_lookup(struct upb_context *c,
-                                            struct upb_string *symbol);
+bool upb_context_lookup(struct upb_context *c, struct upb_string *symbol,
+                        struct upb_symtab_entry *out_entry);
 
-INLINE struct upb_symtab_entry *upb_context_symbegin(struct upb_context *c) {
-  return (struct upb_symtab_entry*)upb_strtable_begin(&c->symtab);
-}
-
-INLINE struct upb_symtab_entry *upb_context_symnext(
-    struct upb_context *c, struct upb_symtab_entry *cur) {
-  return (struct upb_symtab_entry*)upb_strtable_next(&c->symtab, &cur->e);
-}
+/* For enumerating over the entries in the symbol table.  The enumerator
+ * callback will be called once for every symtab entry.
+ *
+ * The callback *must not* block or take any significant amount of time, since
+ * the upb_context's lock is held while it is being called! */
+typedef void (*upb_context_enumerator_t)(
+    void *udata, struct upb_symtab_entry *entry);
+void upb_context_enumerate(struct upb_context *c, upb_context_enumerator_t,
+                           void *udata);
 
 /* Adding symbols. ************************************************************/
 

src/upb_string.h

@@ -60,7 +60,7 @@ INLINE void upb_struninit(struct upb_string *str)
   if(str->byte_size) free(str->ptr);
 }
 
-INLINE struct upb_string *upb_strnew()
+INLINE struct upb_string *upb_strnew(void)
 {
   struct upb_string *str = (struct upb_string*)malloc(sizeof(*str));
   upb_strinit(str);