add call-with-vm; remove thread-vm bits; remove vm-apply; engines settable.

* libguile/vm.h (scm_c_vm_run): Make internal.
* libguile/vm.c (vm_default_engine): New static global variable.
  (make_vm): Set vp->engine based on
  (scm_vm_apply): Remove in favor of call-with-vm.
  (scm_thread_vm, scm_set_thread_vm_x): Remove these, as they did not
  have a well-defined meaning, and were dangerous to call on other
  threads.
  (scm_the_vm): Reinstate previous definition.
  (symbol_to_vm_engine, vm_engine_to_symbol)
  (vm_has_pending_computation): New helpers.
  (scm_vm_engine, scm_set_vm_engine_x, scm_c_set_vm_engine_x): New
  accessors for VM engines.
  (scm_c_set_default_vm_engine_x, scm_set_default_vm_engine_x): New
  setters for the default VM engine.
  (scm_call_with_vm): New function, applies a procedure to arguments in
  a context in which a given VM is current.

* libguile/eval.c (eval, scm_apply): VM dispatch goes through
  scm_call_with_vm.

* test-suite/tests/control.test ("the-vm"):
* module/system/vm/coverage.scm (with-code-coverage): Use call-with-vm.

* module/system/vm/vm.scm: Update exports.

* test-suite/vm/run-vm-tests.scm (run-vm-program):
* test-suite/tests/compiler.test ("current-reader"): Just rely on the
  result of make-program being an applicable.

* test-suite/tests/eval.test ("stack overflow"): Add a note that this
  test does not test what it should.

test-suite/tests/compiler.test

@@ -19,7 +19,6 @@
   #:use-module (test-suite lib)
   #:use-module (test-suite guile-test)
   #:use-module (system base compile)
-  #:use-module ((system vm vm) #:select (the-vm vm-apply))
   #:use-module ((system vm program) #:select (make-program
                                               program-sources source:addr)))
 
@@ -98,7 +97,7 @@
                      #f)
                    (install-reader!)
                    this-should-be-ignored")))
-      (and (eq? (vm-apply (the-vm) (make-program (read-and-compile input)) '())
+      (and (eq? ((make-program (read-and-compile input)))
                 'ok)
            (eq? r (fluid-ref current-reader)))))
 

test-suite/tests/control.test

@@ -238,15 +238,7 @@
                      (p x y))))
       (catch 'foo
         (lambda ()
-          (dynamic-wind
-            (lambda ()
-              (set-thread-vm! (current-thread) new-vm))
-            (lambda ()
-              (vm-apply new-vm
-                        (lambda () (throw 'foo (the-vm)))
-                        '()))
-            (lambda ()
-              (set-thread-vm! (current-thread) prev-vm))))
+          (call-with-vm new-vm (lambda () (throw 'foo (the-vm)))))
         (lambda (key vm)
           (and (eq? key 'foo)
                (eq? vm new-vm)

test-suite/tests/eval.test

@@ -18,7 +18,7 @@
 (define-module (test-suite test-eval)
   :use-module (test-suite lib)
   :use-module ((srfi srfi-1) :select (unfold count))
-  :use-module ((system vm vm) :select (make-vm vm-apply))
+  :use-module ((system vm vm) :select (make-vm call-with-vm))
   :use-module (ice-9 documentation))
 
 
@@ -439,10 +439,11 @@
 
 (with-test-prefix "stack overflow"
 
+  ;; FIXME: this test does not test what it is intending to test
   (pass-if-exception "exception raised"
     exception:vm-error
     (let ((vm    (make-vm))
           (thunk (let loop () (cons 's (loop)))))
-      (vm-apply vm thunk))))
+      (call-with-vm vm thunk))))
 
 ;;; eval.test ends here

test-suite/vm/run-vm-tests.scm

@@ -42,7 +42,7 @@
 
 (define (run-vm-program objcode)
   "Run VM program contained into @var{objcode}."
-  (vm-apply (the-vm) (make-program objcode) '()))
+  ((make-program objcode)))
 
 (define (compile/run-test-from-file file)
   "Run test from source file @var{file} and return a value indicating whether