New configuration option MBEDTLS_CHECK_RETURN_WARNING
MBEDTLS_CHECK_RETURN_TYPICAL defaults off, but is enabled if
MBEDTLS_CHECK_RETURN_WARNING is enabled at compile time.
(MBEDTLS_CHECK_RETURN_CRITICAL is always enabled.)
The default is off so that a plausible program that builds with one version
of Mbed TLS in the default configuration will still build under the next
version.
Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
diff --git a/include/mbedtls/config.h b/include/mbedtls/config.h
index 40b20bd..f5fe085 100644
--- a/include/mbedtls/config.h
+++ b/include/mbedtls/config.h
@@ -617,6 +617,29 @@
//#define MBEDTLS_CAMELLIA_SMALL_MEMORY
/**
+ * \def MBEDTLS_CHECK_RETURN_WARNING
+ *
+ * If this macro is defined, emit a compile-time warning if application code
+ * calls a function without checking its return value, but the return value
+ * should generally be checked in portable applications.
+ *
+ * This is only supported on platforms where #MBEDTLS_CHECK_RETURN is
+ * implemented. Otherwise this option has no effect.
+ *
+ * Uncomment to get warnings on using fallible functions without checking
+ * their return value.
+ *
+ * \note This feature is a work in progress.
+ * Warnings will be added to more functions in the future.
+ *
+ * \note A few functions are considered critical, and ignoring the return
+ * value of these functions will trigger a warning even if this
+ * macro is not defined. To completely disable return value check
+ * warnings, define #MBEDTLS_CHECK_RETURN with an empty expansion.
+ */
+//#define MBEDTLS_CHECK_RETURN_WARNING
+
+/**
* \def MBEDTLS_CIPHER_MODE_CBC
*
* Enable Cipher Block Chaining mode (CBC) for symmetric ciphers.
diff --git a/include/mbedtls/platform_util.h b/include/mbedtls/platform_util.h
index 22ccc89..7e04c4f 100644
--- a/include/mbedtls/platform_util.h
+++ b/include/mbedtls/platform_util.h
@@ -173,7 +173,8 @@
* This macro appearing at the beginning of the declaration of a function
* indicates that its return value should be generally be checked in portable
* applications. Omitting the check will result in a compile-time warning if
- * #MBEDTLS_CHECK_RETURN is implemented for the compiler in use.
+ * #MBEDTLS_CHECK_RETURN is implemented for the compiler in use and
+ * #MBEDTLS_CHECK_RETURN_WARNING is enabled in the compile-time configuration.
*
* \note The use of this macro is a work in progress.
* This macro will be added to more functions in the future.
@@ -181,7 +182,11 @@
* an error code (as \c int in the \c mbedtls_xxx API or
* as ::psa_status_t in the \c psa_xxx API).
*/
+#if defined(MBEDTLS_CHECK_RETURN_WARNING)
#define MBEDTLS_CHECK_RETURN_TYPICAL MBEDTLS_CHECK_RETURN
+#else
+#define MBEDTLS_CHECK_RETURN_TYPICAL
+#endif
/** Benign-failure function
*