[PATCH v3 20/27] revision: always store allocated strings in output encoding

[Patrick Steinhardt <ps@pks.im>]

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The `git_log_output_encoding` variable can be set via the `--encoding=`
option. When doing so, we conditionally either assign it to the passed
value, or if the value is "none" we assign it the empty string.
Depending on which of the both code paths we pick though, the variable
may end up being assigned either an allocated string or a string
constant.

This is somewhat risky and may easily lead to bugs when a different code
path may want to reassign a new value to it, freeing the previous value.
We already to this when parsing the "i18n.logoutputencoding" config in
`git_default_i18n_config()`. But because the config is typically parsed
before we parse command line options this has been fine so far.

Regardless of that, safeguard the code such that the variable always
contains an allocated string. While at it, also free the old value in
case there was any to plug a potential memory leak.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
---
 revision.c             | 3 ++-
 t/t3900-i18n-commit.sh | 1 +
 t/t3901-i18n-patch.sh  | 1 +
 3 files changed, 4 insertions(+), 1 deletion(-)

diff --git a/revision.c b/revision.c
index 7ddf0f151a..2ee6886078 100644
--- a/revision.c
+++ b/revision.c
@@ -2650,10 +2650,11 @@ static int handle_revision_opt(struct rev_info *revs, int argc, const char **arg
 	} else if (!strcmp(arg, "--invert-grep")) {
 		revs->grep_filter.no_body_match = 1;
 	} else if ((argcount = parse_long_opt("encoding", argv, &optarg))) {
+		free(git_log_output_encoding);
 		if (strcmp(optarg, "none"))
 			git_log_output_encoding = xstrdup(optarg);
 		else
-			git_log_output_encoding = "";
+			git_log_output_encoding = xstrdup("");
 		return argcount;
 	} else if (!strcmp(arg, "--reverse")) {
 		revs->reverse ^= 1;
diff --git a/t/t3900-i18n-commit.sh b/t/t3900-i18n-commit.sh
index f27d09cfd9..db7b403bc1 100755
--- a/t/t3900-i18n-commit.sh
+++ b/t/t3900-i18n-commit.sh
@@ -5,6 +5,7 @@
 
 test_description='commit and log output encodings'
 
+TEST_PASSES_SANITIZE_LEAK=true
 . ./test-lib.sh
 
 compare_with () {
diff --git a/t/t3901-i18n-patch.sh b/t/t3901-i18n-patch.sh
index 4b37f78829..5f0b9afc3f 100755
--- a/t/t3901-i18n-patch.sh
+++ b/t/t3901-i18n-patch.sh
@@ -8,6 +8,7 @@ test_description='i18n settings and format-patch | am pipe'
 GIT_TEST_DEFAULT_INITIAL_BRANCH_NAME=main
 export GIT_TEST_DEFAULT_INITIAL_BRANCH_NAME
 
+TEST_PASSES_SANITIZE_LEAK=true
 . ./test-lib.sh
 
 check_encoding () {
-- 
2.45.1.410.g58bac47f8e.dirty


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