invoke conti

or

    conti()

The former is more or less ignored by imcc, the latter is recognized as
a regular function call: registers are preserved and a flag
"sub_calls_a_sub" is set, so that e.g. the return continuation is
preserved around the call. These variants give different output.

How schould it really work?

.sub _main
    .local int a
    a = 1
    _func()
    print a
    print " main\n"
    end
.end

.sub _func
    .local pmc conti
    .local int a
    a = 4
    conti = newcont _end
    _do_something( conti )
_end:
    print a
    print " _func\n"
.end

.sub _do_something
    .param pmc conti
    .local int a
    a = 7
    # invoke conti      # (1)
    conti()             # (2)
    print "error!\n"
.end

Thanks,
leo