Free existing buffers before re-init in BSON value classes

phongo_binary_init, phongo_regex_init, and phongo_javascript_init
overwrote heap-owned struct members without freeing what was already
there. Re-init the slots cleanly so a second call (e.g. from a
subclass that invokes parent::__unserialize twice) does not leak the
prior allocation. As part of this, hoist the regex flags null-byte
check above the pattern allocation so a flag rejection can no longer
leave a stray pattern buffer behind.

Author: alcaeus

src/BSON/Binary.c

@@ -51,6 +51,10 @@ static bool phongo_binary_init(phongo_binary_t* intern, const char* data, size_t
 		return false;
 	}
 
+	if (intern->data) {
+		efree(intern->data);
+	}
+
 	intern->data     = estrndup(data, data_len);
 	intern->data_len = data_len;
 	intern->type     = (uint8_t) type;

src/BSON/Javascript.c

@@ -40,6 +40,14 @@ static bool phongo_javascript_init(phongo_javascript_t* intern, const char* code
 		return false;
 	}
 
+	if (intern->code) {
+		efree(intern->code);
+	}
+	if (intern->scope) {
+		bson_destroy(intern->scope);
+		intern->scope = NULL;
+	}
+
 	intern->code     = estrndup(code, code_len);
 	intern->code_len = code_len;
 

src/BSON/Regex.c

@@ -42,14 +42,23 @@ static bool phongo_regex_init(phongo_regex_t* intern, const char* pattern, size_
 		phongo_throw_exception(PHONGO_ERROR_INVALID_ARGUMENT, "Pattern cannot contain null bytes");
 		return false;
 	}
+
+	if (flags && strlen(flags) != (size_t) flags_len) {
+		phongo_throw_exception(PHONGO_ERROR_INVALID_ARGUMENT, "Flags cannot contain null bytes");
+		return false;
+	}
+
+	if (intern->pattern) {
+		efree(intern->pattern);
+	}
+	if (intern->flags) {
+		efree(intern->flags);
+	}
+
 	intern->pattern     = estrndup(pattern, pattern_len);
 	intern->pattern_len = pattern_len;
 
 	if (flags) {
-		if (strlen(flags) != (size_t) flags_len) {
-			phongo_throw_exception(PHONGO_ERROR_INVALID_ARGUMENT, "Flags cannot contain null bytes");
-			return false;
-		}
 		intern->flags     = estrndup(flags, flags_len);
 		intern->flags_len = flags_len;
 		/* Ensure flags are alphabetized upon initialization */