Throw() with traceback flag within a sub-function crashes JMP

AlterEgo — Fri, 31 Oct 2025 20:12:02 GMT

I 've encountered the following issue (minimal example below). Is this a bug or am I missing something?

(Windows 11, JMP 18.0)

The following script crashes JMP instead of simply throwing the error:

Names Default To Here(1);

f = Function( {}, { sub_f },

	sub_f = Function( {},
		If( 1, Throw( "thrown", 1 ) );			
		Return( "ok" )
	);
	
	Return( sub_f() )
);

f()

In contrast to the above, without the traceback flag, it normally throws the "thrown" error.

Names Default To Here(1);

f = Function( {}, { sub_f },

	sub_f = Function( {},
		If( 1, Throw( "thrown" ) );			
		Return( "ok" )
	);
	
	Return( sub_f() )
);

f()

Also, the crash is prevented by trapping the Return() into Try().

Names Default To Here(1);

f = Function( {}, { sub_f },

	sub_f = Function( {},
		If( 1, Throw( "thrown", 1 ) );			
		Return( "ok" )
	);
	
	Try( Return( sub_f() ), Throw( "crash prevented" ) )
);

f()

Re: Throw() with traceback flag within a sub-function crashes JMP

Craige_Hales — Sat, 01 Nov 2025 11:21:37 GMT

you've found a bug in JMP, I'm submitting a report pointing to this thread. You can work around it by commenting out the local variable for sub_f:

f = Function( {}, // { sub_f },

(Pretty sure this is a reasonably correct explanation...) By the time JMP catches the throw() the local variables are destroyed and the information for the traceback has been lost. The code that produces the traceback is unprepared for that and crashes with an invalid memory reference. When you added the try() inside the function, JMP catches the throw inside the function and the local has not been destroyed. Or, just keep the function in a global will also work.

edit: TS-00250890

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Throw() with traceback flag within a sub-function crashes JMP

Re: Throw() with traceback flag within a sub-function crashes JMP