#603 STOP before an unknown procedure still throws "don't know how to" error

[David Costanzo]

If you define a procedure that runs STOP before reaching a line of code that runs an unknown procedure, the error for the unknown procedure is still thrown. That error is thrown before any instruction line within the procedure executed.

Steps to Reproduce:

TO SHOWBUG
  PRINT [Before STOP]
  STOP
  PRINT [After STOP]
  UNKNOWN1 1
  (UNKNOWN2)
  (UNKNOWN3 1)
END

SHOWBUG

What happens:
FMSLogo throws an error like

I don't know how to UNKNOWN3 in showbug
[(UNKNOWN3 1)]

Expected Result:
The commander prints

Before STOP

Note that UNKNOWN1 1 and (UNKNOWN2) don't throw errors.

This bug is also reproducible in UCBLogo 6.2.5.

This error is only shown when the unknown procedure is run in parentheses and has arguments.

This feels like a bug in that it's surprising. From the Logo programmer's point of view, why should adding parens change the behavior and only then if there are arguments? And for an interpreted language, why does an error on a line that isn't run supersede running any lines?

I encountered this while trying to update the regression tests to be runnable on GNU/Linux. I wasn't able to exit early from the test procedure by adding this:

    IF NOT ISWINDOWS [ STOP ] ; This test only runs on Windows

Because a subsequent call to (DLLFREE "gdi32.dll) halted the tests with an error.

[David Costanzo]

I have committed [r6379] to fix this. It will be available in FMSLogo 8.6.0.

The fix works if the unknown procedure is on a different line from the STOP. A bug still exists if they are on the same line. That is tracked by Bug #625.