Improved fix for test_memeq_hex leak.

The earlier fix would only handle the success case.  In the failing
case, test_mem_op does a goto done, which would leave the leak leaking.

src/test/test.h

@@ -51,14 +51,16 @@
 #define test_memeq(expr1, expr2, len) test_mem_op((expr1), ==, (expr2), len)
 #define test_memneq(expr1, expr2, len) test_mem_op((expr1), !=, (expr2), len)
 
+/* As test_mem_op, but decodes 'hex' before comparing.  There must be a
+ * local char* variable called mem_op_hex_tmp for this to work. */
 #define test_mem_op_hex(expr1, op, hex)                                 \
   STMT_BEGIN                                                            \
   size_t length = strlen(hex);                                          \
-  char *value2 = tor_malloc(length/2);                                  \
+  tor_free(mem_op_hex_tmp);                                             \
+  mem_op_hex_tmp = tor_malloc(length/2);                                \
   tor_assert((length&1)==0);                                            \
-  base16_decode(value2, length/2, hex, length);                         \
-  test_mem_op(expr1, op, value2, length/2);                             \
-  tor_free(value2);                                                     \
+  base16_decode(mem_op_hex_tmp, length/2, hex, length);                 \
+  test_mem_op(expr1, op, mem_op_hex_tmp, length/2);                     \
   STMT_END
 
 #define test_memeq_hex(expr1, hex) test_mem_op_hex(expr1, ==, hex)

src/test/test_crypto.c

@@ -96,6 +96,7 @@ test_crypto_aes(void)
   char *data1 = NULL, *data2 = NULL, *data3 = NULL;
   crypto_cipher_env_t *env1 = NULL, *env2 = NULL;
   int i, j;
+  char *mem_op_hex_tmp=NULL;
 
   data1 = tor_malloc(1024);
   data2 = tor_malloc(1024);
@@ -210,6 +211,7 @@ test_crypto_aes(void)
   test_assert(tor_mem_is_zero(data2, 64));
 
  done:
+  tor_free(mem_op_hex_tmp);
   if (env1)
     crypto_free_cipher_env(env1);
   if (env2)
@@ -229,6 +231,7 @@ test_crypto_sha(void)
   char digest[32];
   char data[50];
   char d_out1[DIGEST_LEN], d_out2[DIGEST256_LEN];
+  char *mem_op_hex_tmp=NULL;
 
   /* Test SHA-1 with a test vector from the specification. */
   i = crypto_digest(data, "abc", 3);
@@ -312,6 +315,7 @@ test_crypto_sha(void)
     crypto_free_digest_env(d1);
   if (d2)
     crypto_free_digest_env(d2);
+  tor_free(mem_op_hex_tmp);
 }
 
 /** Run unit tests for our public key crypto functions */