basic/strv: fix strv_join for first empty argument

Empty strings were ignored in strv_join, but only if they were at the beginning
of the string. Empty strings after at least one non-empty item were treated
normally.

Previously:
{"x"} → "x"
{"x", ""} → "x"
{"x", "", ""} → "x::"
{""} → ""
{"", ""} → ""
{"", "", ""} → ""
{"", "x"} → "x"
{"", "x", ""} → "x:"
Now:
{"x"} → "x"
{"x", ""} → "x"
{"x", "", ""} → "x::"
{""} → ""
{"", ""} → ":"
{"", "", ""} → "::"
{"", "x"} → ":x"
{"", "x", ""} → ":x:"

2 files changed, 25 insertions, 3 deletions

diff --git a/src/basic/strv.c b/src/basic/strv.c
index b5d4d8191b..8282298dca 100644
--- a/src/basic/strv.c
+++ b/src/basic/strv.c
@@ -371,7 +371,7 @@ char *strv_join(char **l, const char *separator) {
 
         n = 0;
         STRV_FOREACH(s, l) {
-                if (n != 0)
+                if (s != l)
                         n += k;
                 n += strlen(*s);
         }
@@ -382,7 +382,7 @@ char *strv_join(char **l, const char *separator) {
 
         e = r;
         STRV_FOREACH(s, l) {
-                if (e != r)
+                if (s != l)
                         e = stpcpy(e, separator);
 
                 e = stpcpy(e, *s);
diff --git a/src/test/test-strv.c b/src/test/test-strv.c
index 2b2f76cc7f..ef451c6abf 100644
--- a/src/test/test-strv.c
+++ b/src/test/test-strv.c
@@ -70,6 +70,18 @@ static const char* const input_table_none[] = {
         NULL,
 };
 
+static const char* const input_table_two_empties[] = {
+        "",
+        "",
+        NULL,
+};
+
+static const char* const input_table_one_empty[] = {
+        "",
+        NULL,
+};
+
+
 static const char* const input_table_quotes[] = {
         "\"",
         "'",
@@ -130,7 +142,7 @@ static void test_strv_find_startswith(void) {
 }
 
 static void test_strv_join(void) {
-        _cleanup_free_ char *p = NULL, *q = NULL, *r = NULL, *s = NULL, *t = NULL;
+        _cleanup_free_ char *p = NULL, *q = NULL, *r = NULL, *s = NULL, *t = NULL, *v = NULL, *w = NULL;
 
         p = strv_join((char **)input_table_multiple, ", ");
         assert_se(p);
@@ -151,6 +163,14 @@ static void test_strv_join(void) {
         t = strv_join((char **)input_table_none, ", ");
         assert_se(t);
         assert_se(streq(t, ""));
+
+        v = strv_join((char **)input_table_two_empties, ", ");
+        assert_se(v);
+        assert_se(streq(v, ", "));
+
+        w = strv_join((char **)input_table_one_empty, ", ");
+        assert_se(w);
+        assert_se(streq(w, ""));
 }
 
 static void test_strv_quote_unquote(const char* const *split, const char *quoted) {
@@ -653,6 +673,8 @@ int main(int argc, char *argv[]) {
         test_strv_quote_unquote(input_table_multiple, "\"one\" \"two\" \"three\"");
         test_strv_quote_unquote(input_table_one, "\"one\"");
         test_strv_quote_unquote(input_table_none, "");
+        test_strv_quote_unquote(input_table_one_empty, "\"\"");
+        test_strv_quote_unquote(input_table_two_empties, "\"\" \"\"");
         test_strv_quote_unquote(input_table_quotes, QUOTES_STRING);
         test_strv_quote_unquote(input_table_spaces, SPACES_STRING);