From e11e81413d46577503d20a93ce7e791bf4324d2b Mon Sep 17 00:00:00 2001
From: Chris Jones <christopher.jones@arm.com>
Date: Thu, 22 Apr 2021 15:28:56 +0100
Subject: [PATCH] Improve documentation for error code checking

Improve comments explaining error code checking, fix incorrect comments
and make a small formatting fix.

Signed-off-by: Chris Jones <christopher.jones@arm.com>
---
 include/mbedtls/error.h |  2 +-
 library/ssl_cookie.c    |  2 +-
 tests/src/helpers.c     | 20 ++++++++++++++++----
 3 files changed, 18 insertions(+), 6 deletions(-)

diff --git a/include/mbedtls/error.h b/include/mbedtls/error.h
index 3d8a5eac0..52b818808 100644
--- a/include/mbedtls/error.h
+++ b/include/mbedtls/error.h
@@ -122,7 +122,7 @@ extern "C" {
 /**
  * \brief Combines a high-level and low-level error code together.
  *
- *        Wrapper function for mbedtls_err_add_ext(). See that function for
+ *        Wrapper macro for mbedtls_error_add_ext(). See that function for
  *        more details.
  */
 #define MBEDTLS_ERROR_ADD( high, low ) \
diff --git a/library/ssl_cookie.c b/library/ssl_cookie.c
index b64c354e6..69d1b3287 100644
--- a/library/ssl_cookie.c
+++ b/library/ssl_cookie.c
@@ -220,7 +220,7 @@ int mbedtls_ssl_cookie_check( void *p_ctx,
 
 #if defined(MBEDTLS_THREADING_C)
     if( mbedtls_mutex_unlock( &ctx->mutex ) != 0 )
-        return( MBEDTLS_ERROR_ADD( MBEDTLS_ERR_SSL_INTERNAL_ERROR ,
+        return( MBEDTLS_ERROR_ADD( MBEDTLS_ERR_SSL_INTERNAL_ERROR,
                 MBEDTLS_ERR_THREADING_MUTEX_ERROR ) );
 #endif
 
diff --git a/tests/src/helpers.c b/tests/src/helpers.c
index b54661195..4923e3c68 100644
--- a/tests/src/helpers.c
+++ b/tests/src/helpers.c
@@ -298,22 +298,34 @@ void mbedtls_test_err_add_check( int high, int low,
      * h = high level error code (includes high and module error codes).
      * l = low level error code.
      */
-    if ( high > -0x1000 && high != 0 )  // high < 0001000000000000
+    if ( high > -0x1000 && high != 0 )
+    /* high < 0001000000000000
+     * No high level error bits are set.
+     */
     {
         mbedtls_test_fail( "'high' is not a high-level error code",
                             line, file );
     }
-    else if ( high < -0x7F80 )          // high > 0111111110000000
+    else if ( high < -0x7F80 )
+    /* high > 0111111110000000
+     * Error code is larger than the greatest high + module level error.
+     */
     {
         mbedtls_test_fail( "'high' error code is greater than 15 bits",
                             line, file );
     }
-    else if ( ( high & 0x7F ) != 0 )    // high & 0000000001111111
+    else if ( ( high & 0x7F ) != 0 )
+    /* high & 0000000001111111
+     * Error code contains low level error code bits.
+     */
     {
         mbedtls_test_fail( "'high' contains a low-level error code",
                             line, file );
     }
-    else if ( low < -0x007F )           // low >  0000000001111111
+    else if ( low < -0x007F )
+    /* low >  0000000001111111
+     * Error code contains high or module level error code bits.
+     */
     {
         mbedtls_test_fail( "'low' error code is greater than 7 bits",
                             line, file );