_swix bug

I’ve spent the afternoon tracking down a bug which turned out to be in _swix – I don’t know if its known about so I thought I’d mention it.

When using OS_ReadVarVal to enumerate a variable name using wildcards the final enumeraton results in an error – which the documentation says should be ignored. However probably because of the error _swix doesn’t update the output variables properly. eg return 0 in R3 _kernel_swi works correctly.

The same bug/feature is in cc 5.70 and cc 5.65.

It’s not a bug, more an oddity of OS_ReadVarVal.
To use that from C, you should use the function in AsmUtils, indeed the exact observation you’ve made is covered in the header file for the function.

I wasn’t measuring the length of the string.