[PATCH v2 6/6] determine_author_info: copy getenv output

[Jeff King <peff@peff.net>]

When figuring out the author name for a commit, we may end
up either pointing to const storage from getenv("GIT_AUTHOR_*"),
or to newly allocated storage based on an existing commit or
the --author option.

Using const pointers to getenv's return has two problems:

  1. It is not guaranteed that the return value from getenv
     remains valid across multiple calls.

  2. We do not know whether to free the values at the end,
     so we just leak them.

We can solve both by duplicating the string returned by
getenv().

Signed-off-by: Jeff King <peff@peff.net>
---
 builtin/commit.c | 40 +++++++++++++++++++++++++++-------------
 1 file changed, 27 insertions(+), 13 deletions(-)

diff --git a/builtin/commit.c b/builtin/commit.c
index 57b046b..7f9f071 100644
--- a/builtin/commit.c
+++ b/builtin/commit.c
@@ -535,15 +535,26 @@ static int parse_force_date(const char *in, struct strbuf *out)
 	return 0;
 }
 
+static void set_ident_var(char **buf, char *val)
+{
+	free(*buf);
+	*buf = val;
+}
+
+static char *envdup(const char *var)
+{
+	const char *val = getenv(var);
+	return val ? xstrdup(val) : NULL;
+}
+
 static void determine_author_info(struct strbuf *author_ident)
 {
 	char *name, *email, *date;
 	struct ident_split author;
-	struct strbuf date_buf = STRBUF_INIT;
 
-	name = getenv("GIT_AUTHOR_NAME");
-	email = getenv("GIT_AUTHOR_EMAIL");
-	date = getenv("GIT_AUTHOR_DATE");
+	name = envdup("GIT_AUTHOR_NAME");
+	email = envdup("GIT_AUTHOR_EMAIL");
+	date = envdup("GIT_AUTHOR_DATE");
 
 	if (author_message) {
 		struct ident_split ident;
@@ -556,15 +567,16 @@ static void determine_author_info(struct strbuf *author_ident)
 		if (split_ident_line(&ident, a, len) < 0)
 			die(_("commit '%s' has malformed author line"), author_message);
 
-		name = xmemdupz(ident.name_begin, ident.name_end - ident.name_begin);
-		email = xmemdupz(ident.mail_begin, ident.mail_end - ident.mail_begin);
+		set_ident_var(&name, xmemdupz(ident.name_begin, ident.name_end - ident.name_begin));
+		set_ident_var(&email, xmemdupz(ident.mail_begin, ident.mail_end - ident.mail_begin));
+
 		if (ident.date_begin) {
-			strbuf_reset(&date_buf);
+			struct strbuf date_buf = STRBUF_INIT;
 			strbuf_addch(&date_buf, '@');
 			strbuf_add(&date_buf, ident.date_begin, ident.date_end - ident.date_begin);
 			strbuf_addch(&date_buf, ' ');
 			strbuf_add(&date_buf, ident.tz_begin, ident.tz_end - ident.tz_begin);
-			date = date_buf.buf;
+			set_ident_var(&date, strbuf_detach(&date_buf, NULL));
 		}
 	}
 
@@ -573,15 +585,15 @@ static void determine_author_info(struct strbuf *author_ident)
 
 		if (split_ident_line(&ident, force_author, strlen(force_author)) < 0)
 			die(_("malformed --author parameter"));
-		name = xmemdupz(ident.name_begin, ident.name_end - ident.name_begin);
-		email = xmemdupz(ident.mail_begin, ident.mail_end - ident.mail_begin);
+		set_ident_var(&name, xmemdupz(ident.name_begin, ident.name_end - ident.name_begin));
+		set_ident_var(&email, xmemdupz(ident.mail_begin, ident.mail_end - ident.mail_begin));
 	}
 
 	if (force_date) {
-		strbuf_reset(&date_buf);
+		struct strbuf date_buf = STRBUF_INIT;
 		if (parse_force_date(force_date, &date_buf))
 			die(_("invalid date format: %s"), force_date);
-		date = date_buf.buf;
+		set_ident_var(&date, strbuf_detach(&date_buf, NULL));
 	}
 
 	strbuf_addstr(author_ident, fmt_ident(name, email, date, IDENT_STRICT));
@@ -592,7 +604,9 @@ static void determine_author_info(struct strbuf *author_ident)
 		export_one("GIT_AUTHOR_DATE", author.date_begin, author.tz_end, '@');
 	}
 
-	strbuf_release(&date_buf);
+	free(name);
+	free(email);
+	free(date);
 }
 
 static void split_ident_or_die(struct ident_split *id, const struct strbuf *buf)
-- 
2.1.0.346.ga0367b9