Allow enabling of dummy error_strerror() to support some use-cases

Enable a dummy error function to make use of error_strerror() in
third party libraries easier.

Disable if you run into name conflicts and want to really remove the
error_strerror()

ChangeLog

@@ -1,5 +1,9 @@
 PolarSSL ChangeLog
 
+= Development
+Changes
+   * Allow enabling of dummy error_strerror() to support some use-cases
+
 = Version 1.2.4 released 2013-01-25
 Changes
    * Added ssl_handshake_step() to allow single stepping the handshake process

include/polarssl/config.h

@@ -160,6 +160,17 @@
 #define POLARSSL_ENABLE_WEAK_CIPHERSUITES
  */
 
+/**
+ * \def POLARSSL_ERROR_STRERROR_DUMMY
+ *
+ * Enable a dummy error function to make use of error_strerror() in
+ * third party libraries easier.
+ *
+ * Disable if you run into name conflicts and want to really remove the
+ * error_strerror()
+ */
+#define POLARSSL_ERROR_STRERROR_DUMMY
+
 /**
  * \def POLARSSL_GENPRIME
  *

library/error.c

@@ -553,4 +553,22 @@ void error_strerror( int ret, char *buf, size_t buflen )
     snprintf( buf, buflen, "UNKNOWN ERROR CODE (%04X)", use_ret );
 }
 
+#else /* POLARSSL_ERROR_C */
+
+#if defined(POLARSSL_ERROR_STRERROR_DUMMY)
+
+#include <string.h>
+
+/*
+ * Provide an non-function in case POLARSSL_ERROR_C is not defined
+ */
+void error_strerror( int ret, char *buf, size_t buflen )
+{
+    ((void) ret);
+
+    if( buflen > 0 )
+        buf[0] = '\0';
+}
+
+#endif /* POLARSSL_ERROR_STRERROR_DUMMY */
 #endif /* POLARSSL_ERROR_C */

programs/util/strerror.c

@@ -38,13 +38,13 @@
 #define USAGE \
     "\n usage: strerror <errorcode>\n"
 
-#if !defined(POLARSSL_ERROR_C) 
+#if !defined(POLARSSL_ERROR_C) && !defined(POLARSSL_ERROR_STRERROR_DUMMY)
 int main( int argc, char *argv[] )
 {
     ((void) argc);
     ((void) argv);
 
-    printf("POLARSSL_ERROR_C not defined.\n");
+    printf("POLARSSL_ERROR_C and/or POLARSSL_ERROR_STRERRO_DUMMY not defined.\n");
     return( 0 );
 }
 #else