Index: src/OFExceptions.h
==================================================================
--- src/OFExceptions.h
+++ src/OFExceptions.h
@@ -132,10 +132,20 @@
 /**
  * An OFException indicating the given value is out of range. 
  */
 @interface OFOutOfRangeException: OFException {}
 /**
+ * \return An error message for the exception as a C String
+ */
+- (char*)cString;
+@end
+
+/**
+ * An OFException indicating that the conversation between two charsets failed.
+ */
+@interface OFCharsetConversionFailedException: OFException {}
+/**
  * \return An error message for the exception as a C String
  */
 - (char*)cString;
 @end
 

Index: src/OFExceptions.m
==================================================================
--- src/OFExceptions.m
+++ src/OFExceptions.m
@@ -140,10 +140,23 @@
 		return string;
 
 	asprintf(&string, "Value out of range in object of class %s!",
 	    object != nil ? [object name] : "(null)");
 
+	return string;
+}
+@end
+
+@implementation OFCharsetConversionFailedException
+- (char*)cString
+{
+	if (string != NULL)
+		return string;
+	
+	asprintf(&string, "Charset conversion failed in object of classs %s!",
+	    [object name]);
+
 	return string;
 }
 @end
 
 @implementation OFOpenFileFailedException

Index: src/OFString.m
==================================================================
--- src/OFString.m
+++ src/OFString.m
@@ -51,13 +51,13 @@
 		if (str == NULL) {
 			length = 0;
 			string = NULL;
 		} else {
 			if ((length = mbstowcs(NULL, str, 0)) == (size_t)-1) {
-				/* FIXME: Throw exception */
 				[super free];
-				return nil;
+				@throw [OFCharsetConversionFailedException
+				    newWithObject: nil];
 			}
 
 			string = [self getMemForNItems: length + 1
 						ofSize: sizeof(wchar_t)];
 
@@ -91,21 +91,18 @@
 - (char*)getCString
 {
 	char *str;
 	size_t len;
 
-	if ((len = wcstombs(NULL, string, 0)) == (size_t)-1) {
-		/* FIXME: Throw exception */
-		return NULL;
-	}
+	if ((len = wcstombs(NULL, string, 0)) == (size_t)-1)
+		@throw [OFCharsetConversionFailedException newWithObject: self];
 
 	str = [self getMemWithSize: len + 1];
 
 	if (wcstombs(str, string, len + 1) != len) {
-		/* FIXME: Throw exception */
 		[self freeMem: str];
-		return NULL;
+		@throw [OFCharsetConversionFailedException newWithObject: self];
 	}
 
 	return str;
 }
 
@@ -146,22 +143,19 @@
 	size_t	newlen, strlength;
 
 	if (string == NULL) 
 		return [self setTo: [OFString newFromCString: str]];
 
-	if ((strlength = mbstowcs(NULL, str, 0)) == (size_t)-1) {
-		/* FIXME: Throw exception */
-		return nil;
-	} 
+	if ((strlength = mbstowcs(NULL, str, 0)) == (size_t)-1)
+		@throw [OFCharsetConversionFailedException newWithObject: self];
 
 	tmpstr = [self getMemForNItems: strlength + 1
 				ofSize: sizeof(wchar_t)];
 
 	if (mbstowcs(tmpstr, str, strlength) != strlength) {
-		/* FIXME: Throw exception */
 		[self freeMem: tmpstr];
-		return nil;
+		@throw [OFCharsetConversionFailedException newWithObject: self];
 	}
 
 	newlen = length + strlength;
 	newstr = [self resizeMem: string
 			toNItems: newlen + 1