builtin/help: fix leaks in `check_git_cmd()`

The `check_git_cmd()` function is declared to return a string constant.
And while it sometimes does return a constant, it may also return an
allocated string in two cases:

  - When handling aliases. This case is already marked with `UNLEAK()`
    to work around the leak.

  - When handling unknown commands in case "help.autocorrect" is
    enabled. This one is not marked with `UNLEAK()`.

The function only has a single caller, so let's fix its return type to
be non-constant, consistently return an allocated string and free it at
its callsite to plug the leak.

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

diff --git a/builtin/help.c b/builtin/help.c
index 4a5a0790704b402e6f989118a0f90b52eb49dae1..6a72d991a84d9f14ecb8a711a012ed544450ca1c 100644 (file)
--- a/builtin/help.c
+++ b/builtin/help.c
@@ -551,12 +551,12 @@ static void show_html_page(const char *page)
        open_html(page_path.buf);
 }
 
-static const char *check_git_cmd(const char* cmd)
+static char *check_git_cmd(const char *cmd)
 {
        char *alias;
 
        if (is_git_command(cmd))
-               return cmd;
+               return xstrdup(cmd);
 
        alias = alias_lookup(cmd);
        if (alias) {
@@ -589,14 +589,13 @@ static const char *check_git_cmd(const char* cmd)
                        die(_("bad alias.%s string: %s"), cmd,
                            split_cmdline_strerror(count));
                free(argv);
-               UNLEAK(alias);
                return alias;
        }
 
        if (exclude_guides)
                return help_unknown_cmd(cmd);
 
-       return cmd;
+       return xstrdup(cmd);
 }
 
 static void no_help_format(const char *opt_mode, enum help_format fmt)
@@ -642,6 +641,7 @@ int cmd_help(int argc,
 {
        int nongit;
        enum help_format parsed_help_format;
+       char *command = NULL;
        const char *page;
 
        argc = parse_options(argc, argv, prefix, builtin_help_options,
@@ -713,9 +713,9 @@ int cmd_help(int argc,
        if (help_format == HELP_FORMAT_NONE)
                help_format = parse_help_format(DEFAULT_HELP_FORMAT);
 
-       argv[0] = check_git_cmd(argv[0]);
+       command = check_git_cmd(argv[0]);
 
-       page = cmd_to_page(argv[0]);
+       page = cmd_to_page(command);
        switch (help_format) {
        case HELP_FORMAT_NONE:
        case HELP_FORMAT_MAN:
@@ -729,5 +729,6 @@ int cmd_help(int argc,
                break;
        }
 
+       free(command);
        return 0;
 }