Merge pull request #10651 from yuwata/fix-10598

conf-parser: ignore trailing back-slash in comment

man/systemd.syntax.xml

@@ -73,7 +73,8 @@
     backslash is replaced by a space character. This may be used to wrap long lines. The limit on
     line length is very large (currently 1 MB), but it is recommended to avoid such long lines and
     use multiple directives, variable substitution, or other mechanism as appropriate for the given
-    file type.</para>
+    file type. When a comment line or lines follow a line ending with a backslash, the comment block
+    is ignored, so the continued line is concatenated with whatever follows the comment block.</para>
 
     <example><programlisting>[Section A]
 KeyOne=value 1
@@ -85,6 +86,12 @@ KeyTwo=value 2
 Setting="something" "some thing" "…"
 KeyTwo=value 2 \
        value 2 continued
+
+[Section C]
+KeyThree=value 2\
+# this line is ignored
+; this line is ignored too
+       value 2 continued
 </programlisting></example>
 
     <para>Boolean arguments used in configuration files can be written in

src/shared/conf-parser.c

@@ -174,7 +174,7 @@ static int parse_line(
         if (!*l)
                 return 0;
 
-        if (strchr(COMMENTS "\n", *l))
+        if (*l == '\n')
                 return 0;
 
         include = first_word(l, ".include");
@@ -327,6 +327,9 @@ int config_parse(const char *unit,
                         return r;
                 }
 
+                if (strchr(COMMENTS, *buf))
+                        continue;
+
                 l = buf;
                 if (!(flags & CONFIG_PARSE_REFUSE_BOM)) {
                         char *q;

src/test/test-conf-parser.c

@@ -274,6 +274,18 @@ static const char* const config_file[] = {
         "2\\\n"
         "3\n",
 
+        "[Section]\n"
+        "#hogehoge\\\n"      /* continuation is ignored in comment */
+        "setting1=1\\\n"     /* normal continuation */
+        "2\\\n"
+        "3\n",
+
+        "[Section]\n"
+        "setting1=1\\\n"     /* normal continuation */
+        "#hogehoge\\\n"      /* commented out line in continuation is ignored */
+        "2\\\n"
+        "3\n",
+
         "[Section]\n"
         "setting1=1\\\n"     /* continuation with extra trailing backslash at the end */
         "2\\\n"
@@ -350,27 +362,27 @@ static void test_config_parse(unsigned i, const char *s) {
                 assert_se(streq(setting1, "1"));
                 break;
 
-        case 4 ... 5:
+        case 4 ... 7:
                 assert_se(r == 0);
                 assert_se(streq(setting1, "1 2 3"));
                 break;
 
-        case 6:
+        case 8:
                 assert_se(r == 0);
                 assert_se(streq(setting1, "1\\\\ \\\\2"));
                 break;
 
-        case 7:
+        case 9:
                 assert_se(r == 0);
                 assert_se(streq(setting1, x1000("ABCD")));
                 break;
 
-        case 8 ... 9:
+        case 10 ... 11:
                 assert_se(r == 0);
                 assert_se(streq(setting1, x1000("ABCD") " foobar"));
                 break;
 
-        case 10 ... 11:
+        case 12 ... 13:
                 assert_se(r == -ENOBUFS);
                 assert_se(setting1 == NULL);
                 break;