[PATCH/RFC] commit: fix memory-leak

[Erik Faye-Lund <kusmabite@gmail.com>]

The name, email and date strings are some times allocated on the
heap, but not free'd. Fix this by making sure they are allways
heap-allocated, so we can safely free the memory.

At the same time, this fixes a problem with strict-POSIX getenv
implementations. POSIX says "The return value from getenv() may
point to static data which may be overwritten by subsequent calls
to getenv()", so duplicating the strings is a potential bug.

Signed-off-by: Erik Faye-Lund <kusmabite@gmail.com>
---

This was found when investigating how to fix UTF-8 support in
getenv on Windows. I introduced the xgetenv-function (that returns
a pointer that can be passed to free) because I suspect we'll find
other similar code-paths.

 builtin/commit.c  |    9 ++++++---
 git-compat-util.h |    1 +
 wrapper.c         |    6 ++++++
 3 files changed, 13 insertions(+), 3 deletions(-)

diff --git a/builtin/commit.c b/builtin/commit.c
index 03cff5a..e5a649e 100644
--- a/builtin/commit.c
+++ b/builtin/commit.c
@@ -465,9 +465,9 @@ static void determine_author_info(struct strbuf *author_ident)
 {
 	char *name, *email, *date;
 
-	name = getenv("GIT_AUTHOR_NAME");
-	email = getenv("GIT_AUTHOR_EMAIL");
-	date = getenv("GIT_AUTHOR_DATE");
+	name = xgetenv("GIT_AUTHOR_NAME");
+	email = xgetenv("GIT_AUTHOR_EMAIL");
+	date = xgetenv("GIT_AUTHOR_DATE");
 
 	if (use_message && !renew_authorship) {
 		const char *a, *lb, *rb, *eol;
@@ -507,6 +507,9 @@ static void determine_author_info(struct strbuf *author_ident)
 		date = force_date;
 	strbuf_addstr(author_ident, fmt_ident(name, email, date,
 					      IDENT_ERROR_ON_NO_NAME));
+	free(name);
+	free(email);
+	free(date);
 }
 
 static int ends_rfc2822_footer(struct strbuf *sb)
diff --git a/git-compat-util.h b/git-compat-util.h
index d6d269f..12f111f 100644
--- a/git-compat-util.h
+++ b/git-compat-util.h
@@ -409,6 +409,7 @@ typedef void (*try_to_free_t)(size_t);
 extern try_to_free_t set_try_to_free_routine(try_to_free_t);
 
 extern char *xstrdup(const char *str);
+extern char *xgetenv(const char *name);
 extern void *xmalloc(size_t size);
 extern void *xmallocz(size_t size);
 extern void *xmemdupz(const void *data, size_t len);
diff --git a/wrapper.c b/wrapper.c
index 8d7dd31..e6173c4 100644
--- a/wrapper.c
+++ b/wrapper.c
@@ -30,6 +30,12 @@ char *xstrdup(const char *str)
 	return ret;
 }
 
+char *xgetenv(const char *name)
+{
+	char *tmp = getenv(name);
+	return tmp ? xstrdup(tmp) : NULL;
+}
+
 void *xmalloc(size_t size)
 {
 	void *ret = malloc(size);
-- 
1.7.4.msysgit.0