Hello,
in my efforts to port GNUstep base to Darwin, I managed to cause
recursively raised exceptions, because the exception handling
code tries to create a new NSString which again raises ...
Of course, some of my code is broken, but this is why Exceptions
exist, don't they?
I found a solution which works for me (see below) but I'm not
fully satisfied:
1) Don't know what to do in case of a recursive exception except
for abort().
2) The name of the exception might be an insufficient identifier.
3) A clean solution wouldn't create new objects except the
NSException itsself and this avoid the chance for recursion at
all.
Here's the modified method for NSException for discussion or use:
+ (void) raise: (NSString*)name
format: (NSString*)format
arguments: (va_list)argList
{
// don't fiddle with malloc() in this critical situation
static unsigned char lastName[64];
NSString *reason;
NSException *except;
/* Avoid recursive Exception raising. This works as long as
long as all NSString methods raise their exception using
this method. */
if (strncmp(lastName, [name cString], 63))
{
strncpy(lastName, [name cString], 63);
} else {
fprintf(stderr, "Recursive Exception detected.\n");
fprintf(stderr, "Name: %s\nReason: ", lastName);
vfprintf(stderr, [format cString], argList);
abort();
}
/* Creating a new NSString here can lead to a recursion */
reason = [NSString stringWithFormat: format arguments: argList];
except = [self exceptionWithName: name reason: reason userInfo: nil];
[except raise];
}
Cheers,
Markus
P.S.: This is the backtrace I get now instead of the 5176 line
one before:
#0 0x7001a70c in kill ()
#1 0x7006f990 in abort ()
#2 0x001e6390 in -[NSException initWithName:reason:userInfo:] ()
#3 0x7006f990 in abort ()
#4 0x002054ec in -[NSObject(GNU) subclassResponsibility:] ()
#5 0x0021f578 in -[NSString length] ()
#6 0x0021ef00 in -[NSString initWithFormat:locale:arguments:] ()
#7 0x0021eeb4 in -[NSString initWithFormat:arguments:] ()
#8 0x0021e740 in +[NSString stringWithFormat:arguments:] ()
#9 0x001e62ec in +[NSException raise:format:arguments:] ()
#10 0x001e6244 in +[NSException raise:format:] ()
#11 0x002054ec in -[NSObject(GNU) subclassResponsibility:] ()
#12 0x0021f578 in -[NSString length] ()
#13 0x001c02fc in +[NSCharacterSet
characterSetWithCharactersInString:] ()
#14 0x0021dfa4 in pathSeps ()
#15 0x00222600 in -[NSString lastPathComponent] ()
#16 0x00212554 in _gnu_process_args ()
#17 0x00212874 in main ()
#18 0x000029cc in _start ()
#19 0x000027fc in start ()
This is what is now shown on the console:
Recursive Exception detected.
Name: NSGenericException
Reason: subclass NSConstantString(instance) should override length
basic has exited due to signal 6 (SIGABRT).
- - - - - - - - - - - - - - - - - - -
Dipl. Ing. Markus Hitter
http://www.jump-ing.de/
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