Add initializers for input / output copies

Signed-off-by: David Horstmann <david.horstmann@arm.com>
diff --git a/library/psa_crypto_core.h b/library/psa_crypto_core.h
index 1a5a389..d378505 100644
--- a/library/psa_crypto_core.h
+++ b/library/psa_crypto_core.h
@@ -520,6 +520,8 @@
     size_t len;
 } psa_crypto_input_copy_t;
 
+#define PSA_CRYPTO_INPUT_COPY_INIT { NULL, 0 }
+
 /** Allocate a local copy of an input buffer.
  *
  * \param[in] input             Pointer to input buffer.
@@ -548,6 +550,8 @@
     size_t len;
 } psa_crypto_output_copy_t;
 
+#define PSA_CRYPTO_OUTPUT_COPY_INIT { NULL, NULL, 0 }
+
 /** Allocate a local copy of an output buffer.
  *
  * \note                        This does not copy any data from the original
diff --git a/tests/suites/test_suite_psa_crypto_memory.function b/tests/suites/test_suite_psa_crypto_memory.function
index 7b6b7f1..e9e5299 100644
--- a/tests/suites/test_suite_psa_crypto_memory.function
+++ b/tests/suites/test_suite_psa_crypto_memory.function
@@ -184,12 +184,9 @@
 {
     uint8_t *output = NULL;
     uint8_t *buffer_copy_for_comparison = NULL;
-    psa_crypto_output_copy_t output_copy;
+    psa_crypto_output_copy_t output_copy = PSA_CRYPTO_OUTPUT_COPY_INIT;
     psa_status_t status;
 
-    output_copy.buffer = NULL;
-    output_copy.len = 0;
-
     if (!original_is_null) {
         TEST_CALLOC(output, output_len);
     }