Failure to insert spaces using "(c-set-offset 'arglist-intro '+)"

[ideasman42]

When using a fixed indent level for multi-line function arguments, tabs are not converted into spaces.

eg:

When using this setting with tab-width set to 4:

(c-set-offset 'arglist-intro '++)

I expect:

--->foobar(
--->........a,
--->........b);

but get:

--->foobar(
--->--->--->a,
--->--->--->b);

Somehow the tabs from arglist-into are interpreted differently.

Using a function that simply returns 8, I get the result I'd expect. eg:

(c-set-offset 'arglist-intro (lambda (pair) 8))