mtkennerly/shawl

Negative exit codes are not handled properly

ilpropheta opened this issue · 5 comments

ilpropheta commented

Hi,
thanks for this awesome tool!

This is just for reporting a possible bug: it seems to me that shawl is handling negative exit codes properly.
For example, this command line below:

shawl.exe add --pass -2 --name MyService -- Process.exe

results in:

error: Found argument '-2' which wasn't expected, or isn't valid in this context
...

I get the same for any arguments involving exit codes (e.g. --restart-if).

Am I missing something?

Thanks!

Marco

mtkennerly commented

Hi! This one is a bit odd. Internally, Windows treats all exit codes as unsigned 32-bit (source), but Command Prompt reinterprets them as signed. You can see it in this example:

>python -c "import sys; sys.exit(2_147_483_647)"
>echo %errorlevel%
2147483647

>python -c "import sys; sys.exit(2_147_483_648)"
>echo %errorlevel%
-1

So I think Shawl's behavior is technically correct, but not necessarily convenient. I'll look into supporting negative codes as a shortcut in add.

ilpropheta commented

Hi @mtkennerly, thanks for your reply! You are totally right, I haven't taken into account this subtlety and mistakenly thought that Shawl was using the prompt "convention".

I think Shawl is right too.

Just to add more value to this discussion, the options I see here:

  1. Shawl supports negative codes and silently turns them into unsigned (e.g. -2 turns to 4294967294);
  2. Shawl supports negative codes and warns the user that it is turning them into unsigned;
  3. Like 3 but only if an explicit flag is used (like --enable-negative-codes or such). This is like getting a sort of acknowledgment from the user ("I know what Shawl is doing");
  4. Shawl keeps on breaking on negative codes but it reports a better error message;
  5. (just for completeness) no action at all.

Probably I am missing some options but I hope these above can be useful for your decision!

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mtkennerly commented

Actually, I'm looking into this now, and the root cause is different than I was thinking earlier. Shawl does support negative numbers, but not at the start of the value, because then it looks like a CLI short flag. For example, --pass 0,-1 is fine, but not --pass -1. The signed/unsigned subtlety I was thinking of is already handled elsewhere.

mtkennerly commented

This is now available in v1.1.1. Let me know if you run into any other issues around this.

ilpropheta commented

Sure, I'll let you know! Many thanks for your support.

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