[libc-test][PATCH] add putenv double-free regression test

[Alexander Monakov <amonakov@ispras.ru>]

---
I see the musl patch has been committed, so here's the corresponding libc-test
regression test.

It's pretty bare-bones since it just relies on libc's built-in double-free
detection.

Also it's pretty lazy to use _GNU_SOURCE ftm to get putenv; I'm not sure
what's the expected style in libc-test for such things though.
src/functional/env.c also uses _GNU_SOURCE.

 src/regression/putenv-doublefree.c | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)
 create mode 100644 src/regression/putenv-doublefree.c

diff --git a/src/regression/putenv-doublefree.c b/src/regression/putenv-doublefree.c
new file mode 100644
index 0000000..f3a1f6c
--- /dev/null
+++ b/src/regression/putenv-doublefree.c
@@ -0,0 +1,16 @@
+// commit 9543656cc32fda48fc463f332ee20e91eed2b768 2016-03-06
+// __putenv could be confused into freeing storage that does not belong to the implementation
+#define _GNU_SOURCE
+#include <stdlib.h>
+#include <string.h>
+
+int main(void)
+{
+	setenv("A", "1", 1);
+	setenv("A", "2", 1);
+	char *c = strdup("A=3");
+	putenv(c);
+	setenv("A", "4", 1);
+	free(c);
+	return 0;
+}
-- 
2.1.3