reftable/basics: handle allocation failures in parse_names()

Handle allocation failures in `parse_names()` by returning `NULL` in
case any allocation fails. While at it, refactor the function to return
the array directly instead of assigning it to an out-pointer.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

reftable/basics.c

@@ -135,14 +135,14 @@ size_t names_length(const char **names)
 	return p - names;
 }
 
-void parse_names(char *buf, int size, char ***namesp)
+char **parse_names(char *buf, int size)
 {
 	char **names = NULL;
 	size_t names_cap = 0;
 	size_t names_len = 0;
-
 	char *p = buf;
 	char *end = buf + size;
+
 	while (p < end) {
 		char *next = strchr(p, '\n');
 		if (next && next < end) {
@@ -152,14 +152,26 @@ void parse_names(char *buf, int size, char ***namesp)
 		}
 		if (p < next) {
 			REFTABLE_ALLOC_GROW(names, names_len + 1, names_cap);
-			names[names_len++] = xstrdup(p);
+			if (!names)
+				goto err;
+
+			names[names_len] = reftable_strdup(p);
+			if (!names[names_len++])
+				goto err;
 		}
 		p = next + 1;
 	}
 
 	REFTABLE_REALLOC_ARRAY(names, names_len + 1);
 	names[names_len] = NULL;
-	*namesp = names;
+
+	return names;
+
+err:
+	for (size_t i = 0; i < names_len; i++)
+		reftable_free(names[i]);
+	reftable_free(names);
+	return NULL;
 }
 
 int names_equal(const char **a, const char **b)

reftable/basics.h

@@ -38,9 +38,12 @@ size_t binsearch(size_t sz, int (*f)(size_t k, void *args), void *args);
  */
 void free_names(char **a);
 
-/* parse a newline separated list of names. `size` is the length of the buffer,
- * without terminating '\0'. Empty names are discarded. */
-void parse_names(char *buf, int size, char ***namesp);
+/*
+ * Parse a newline separated list of names. `size` is the length of the buffer,
+ * without terminating '\0'. Empty names are discarded. Returns a `NULL`
+ * pointer when allocations fail.
+ */
+char **parse_names(char *buf, int size);
 
 /* compares two NULL-terminated arrays of strings. */
 int names_equal(const char **a, const char **b);

reftable/stack.c

@@ -108,7 +108,11 @@ static int fd_read_lines(int fd, char ***namesp)
 	}
 	buf[size] = 0;
 
-	parse_names(buf, size, namesp);
+	*namesp = parse_names(buf, size);
+	if (!*namesp) {
+		err = REFTABLE_OUT_OF_MEMORY_ERROR;
+		goto done;
+	}
 
 done:
 	reftable_free(buf);

t/unit-tests/t-reftable-basics.c

@@ -72,13 +72,14 @@ int cmd_main(int argc UNUSED, const char *argv[] UNUSED)
 	if_test ("parse_names works for basic input") {
 		char in1[] = "line\n";
 		char in2[] = "a\nb\nc";
-		char **out = NULL;
-		parse_names(in1, strlen(in1), &out);
+		char **out = parse_names(in1, strlen(in1));
+		check(out != NULL);
 		check_str(out[0], "line");
 		check(!out[1]);
 		free_names(out);
 
-		parse_names(in2, strlen(in2), &out);
+		out = parse_names(in2, strlen(in2));
+		check(out != NULL);
 		check_str(out[0], "a");
 		check_str(out[1], "b");
 		check_str(out[2], "c");
@@ -88,8 +89,8 @@ int cmd_main(int argc UNUSED, const char *argv[] UNUSED)
 
 	if_test ("parse_names drops empty string") {
 		char in[] = "a\n\nb\n";
-		char **out = NULL;
-		parse_names(in, strlen(in), &out);
+		char **out = parse_names(in, strlen(in));
+		check(out != NULL);
 		check_str(out[0], "a");
 		/* simply '\n' should be dropped as empty string */
 		check_str(out[1], "b");