better error handling in library loader

4 files changed, 26 insertions, 17 deletions

diff --git a/docs/libraries/README b/docs/libraries/README
index 23919c3..f2ecb2a 100644
--- a/docs/libraries/README
+++ b/docs/libraries/README
@@ -19,6 +19,8 @@ Some more unsorted links:
 - On MacX: http://developer.apple.com/mac/library/releasenotes/DeveloperTools/RN-dyld/index.html
 - http://www.flounder.com/loadlibrary_explorer.htm: how LoadLibrary works
   internally (search path for DLLs, security, etc.)
+- http://tldp.org/HOWTO/Program-Library-HOWTO/dl-libraries.html: explainig about
+  the dlerror odity around dlsym
 
 Goal:
 - we want abstractions for varying versions of dlopen/LoadLibrary(Ex) etc.
diff --git a/include/wolf/library/loader.h b/include/wolf/library/loader.h
index 20414c8..2f37da2 100644
--- a/include/wolf/library/loader.h
+++ b/include/wolf/library/loader.h
@@ -99,14 +99,13 @@ wolf_error_t wolf_library_unload( wolf_library_p library );
 /**
  * Converts the last error and state of the library object in a human readable message.
  *
- * @param error     the error which happened after calling a library loader function
  * @param library   the library object for which we want a error message
  * @param buf       the buffer which will hold the error message
  * @param buflen    the size of the buffer
  *
  * @return          a pointer to buf for convenience
  */
-char *wolf_library_errmsg( const wolf_error_t error, const wolf_library_p library, char *buf, size_t buflen );
+char *wolf_library_error_msg( const wolf_library_p library, char *buf, size_t buflen );
 
 /**
  * Gets a symbol (a function) from the library object. It has to be
diff --git a/src/library/loader.c b/src/library/loader.c
index 93b9298..1606557 100644
--- a/src/library/loader.c
+++ b/src/library/loader.c
@@ -93,7 +93,11 @@ wolf_error_t wolf_library_unload( wolf_library_p l ) {
 	BOOL res = FALSE;
 #endif
 
-	if( l == NULL || l->handle == NULL ) {
+	if( l == NULL ) {
+		return WOLF_OK;
+	}
+
+	if( l->handle == NULL ) {
 		return WOLF_ERR_INVALID_STATE;
 	}
 
@@ -121,13 +125,8 @@ wolf_error_t wolf_library_unload( wolf_library_p l ) {
 	return WOLF_OK;
 }
 
-char *wolf_library_errmsg( const wolf_error_t error, const wolf_library_p library, char *buf, size_t buflen ) {
-	(void)wolf_error_msg( error, buf, buflen );
-	strncat( buf, " - ", buflen - strlen( buf ) );
-	if( error == WOLF_ERR_INTERNAL ) {
-		strncat( buf, library->errbuf, buflen - strlen( buf ) );
-	}
-
+char *wolf_library_error_msg(  const wolf_library_p library, char *buf, size_t buflen ) {
+	strncpy( buf, library->errbuf, buflen );
 	return buf;
 }
 
diff --git a/tests/library/test_loader.c b/tests/library/test_loader.c
index bda32b3..75f968b 100644
--- a/tests/library/test_loader.c
+++ b/tests/library/test_loader.c
@@ -26,6 +26,7 @@
 #else
 #define LIBRARY_NAME "./testlib.so.0.0.0"
 #endif
+#define LIBRARY_FUNC "multiply_by_two2"
 
 int main( void ) {
 	wolf_library_p library;
@@ -39,16 +40,22 @@ int main( void ) {
 	/* open the libray */
 	library = wolf_library_load( LIBRARY_NAME, &error );
 	if( error != WOLF_OK ) {
-		fprintf( stderr, "Error %d loading the library: %s\n",
-			error, wolf_library_errmsg( error, library, errbuf, 512 ) );
+		fprintf( stderr, "Error %d (%s) loading library '%s':\n",
+			error, wolf_error_msg( error, errbuf, 512 ), LIBRARY_NAME );
+		fprintf( stderr, "Internal loader error: %s\n",
+			wolf_library_error_msg( library, errbuf, 512 ) );
+		(void)wolf_library_unload( library );
 		return EXIT_FAILURE;
 	}
 
 	/* fetch a known function symbol (multiply_by_two) */
-	symbol = wolf_library_get_func( library, "multiply_by_two", &error );
+	symbol = wolf_library_get_func( library, LIBRARY_FUNC, &error );
 	if( error != WOLF_OK ) {
-		fprintf( stderr, "Error %d fetching a function from the library: %s\n",
-			error, wolf_library_errmsg( error, library, errbuf, 512 ) );
+		fprintf( stderr, "Error %d (%s) fetching function '%s' from the library\n",
+			error, wolf_error_msg( error, errbuf, 512 ), LIBRARY_FUNC );
+		fprintf( stderr, "Internal loader error: %s\n",
+			wolf_library_error_msg( library, errbuf, 512 ) );
+		(void)wolf_library_unload( library );
 		return EXIT_FAILURE;
 	}
 	WOLF_LIBRARY_FUNC_CAST( symbol, multiply_by_two_func, func );
@@ -60,8 +67,10 @@ int main( void ) {
 	/* close library */
 	error = wolf_library_unload( library );
 	if( error != WOLF_OK ) {
-		fprintf( stderr, "Error %d unloading the library: %s\n",
-			error, wolf_library_errmsg( error, library, errbuf, 512 ) );
+		fprintf( stderr, "Error %d (%s) unloading the library\n",
+			error, wolf_error_msg( error, errbuf, 512 ) );
+		fprintf( stderr, "Internal loader error: %s\n",
+			wolf_library_error_msg( library, errbuf, 512 ) );
 		return EXIT_FAILURE;
 	}