Here's what happens if I run the same tests with ##show-all-continuations? set to true. Level 2 adds frames to the backtrace without changing any of level 1's frames. Much more straightforward. Now I don't need so badly to see the continuation tree.
With the line "(generate-proper-tail-calls #f)" added, the results are the same except for line numbers.
-- Derek
Gambit v4.2.4
(set! ##show-all-continuations? #t) (define (a)
(step) (step))
(a)
*** STOPPED IN a, (console)@3.9 1> ,b 0 a (console)@3:9 step 1 a (console)@3:8 (step) 2 (interaction) (console)@4:1 (a) 3 ##eval-within 4 ##dynamic-env-bind 5 ##with-no-result-expected 6 ##repl-debug 7 ##repl-debug-main 8 ##kernel-handlers 1> x *** ERROR IN (console)@6.1 -- Unbound variable: x 2> ,b 0 (interaction) (console)@6:1 x 1 ##eval-within 2 ##dynamic-env-bind 3 a (console)@3:9 step 4 a (console)@3:8 (step) 5 (interaction) (console)@4:1 (a) 6 ##eval-within 7 ##dynamic-env-bind 8 ##with-no-result-expected 9 ##repl-debug 10 ##repl-debug-main 11 ##kernel-handlers 2> ,d 1> ,b 0 a (console)@3:9 step 1 a (console)@3:8 (step) 2 (interaction) (console)@4:1 (a) 3 ##eval-within 4 ##dynamic-env-bind 5 ##with-no-result-expected 6 ##repl-debug 7 ##repl-debug-main 8 ##kernel-handlers 1> ,q