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Frame <binding> objects capture frame, can ref value directly
* module/system/repl/debug.scm (print-locals): Adapt to frame-binding-ref change. * module/system/vm/frame.scm (<binding>): Add `frame' field. (available-bindings): Capture the frame. (binding-ref, binding-set!): New functions, accessing a local variable value directly from a frame. (frame-binding-ref, frame-binding-set!): Remove. As these are very low-level debugging interfaces introduced in 2.0, never documented, and quite tied to the VM, we feel comfortable making this change. (frame-call-representation): Adapt to available-bindings change. (frame-environment, frame-object-binding): Adapt to binding-ref interface change. * doc/ref/vm.texi (Stack Layout): Mention that slots can be re-used. Update disassembly in example. * doc/ref/api-debug.texi (Frames): Remove documentation for frame-local-ref, frame-local-set!, and frame-num-locals. Replace with documentation for frame-bindings, binding accessors, and binding-ref / binding-set!.
This commit is contained in:
Andy Wingo
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4 changed files with 76 additions and 52 deletions
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@ -201,16 +201,32 @@ respectively. @xref{VM Concepts}, for more information.
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@deffnx {Scheme Procedure} frame-mv-return-address frame
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Accessors for the three saved VM registers in a frame: the previous
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frame pointer, the single-value return address, and the multiple-value
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return address. @xref{Stack Layout}, for more information.
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return address. @xref{Stack Layout}, for more information.
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@end deffn
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@deffn {Scheme Procedure} frame-num-locals frame
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@deffnx {Scheme Procedure} frame-local-ref frame i
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@deffnx {Scheme Procedure} frame-local-set! frame i val
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Accessors for the temporary values corresponding to @var{frame}'s
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procedure application. The first local is the first argument given to
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the procedure. After the arguments, there are the local variables, and
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after that temporary values. @xref{Stack Layout}, for more information.
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@deffn {Scheme Procedure} frame-bindings frame
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Return a list of binding records indicating the local variables that are
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live in a frame.
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@end deffn
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@deffn {Scheme Procedure} frame-lookup-binding frame var
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Fetch the bindings in @var{frame}, and return the first one whose name
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is @var{var}, or @code{#f} otherwise.
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@end deffn
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@deffn {Scheme Procedure} binding-index binding
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@deffnx {Scheme Procedure} binding-name binding
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@deffnx {Scheme Procedure} binding-slot binding
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@deffnx {Scheme Procedure} binding-representation binding
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Accessors for the various fields in a binding. The implicit ``callee''
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argument is index 0, the first argument is index 1, and so on to the end
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of the arguments. After that are temporary variables. Note that if a
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variable is dead, it might not be available.
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@end deffn
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@deffn {Scheme Procedure} binding-ref binding
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@deffnx {Scheme Procedure} binding-set! binding val
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Accessors for the values of local variables in a frame.
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@end deffn
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@deffn {Scheme Procedure} display-application frame [port [indent]]
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@ -160,10 +160,18 @@ The structure of the top stack frame is as follows:
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\------------------/ <- sp
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@end example
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In the above drawing, the stack grows downward. Usually the procedure
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being applied is in local 0, followed by the arguments from local 1.
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After that are enough slots to store the various lexically-bound and
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temporary values that are needed in the function's application.
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In the above drawing, the stack grows downward. At the beginning of a
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function call, the procedure being applied is in local 0, followed by
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the arguments from local 1. After the procedure checks that it is being
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passed a compatible set of arguments, the procedure allocates some
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additional space in the frame to hold variables local to the function.
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Note that once a value in a local variable slot is no longer needed,
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Guile is free to re-use that slot. This applies to the slots that were
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initially used for the callee and arguments, too. For this reason,
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backtraces in Guile aren't always able to show all of the arguments: it
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could be that the slot corresponding to that argument was re-used by
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some other variable.
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The @dfn{return address} is the @code{ip} that was in effect before this
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program was applied. When we return from this activation frame, we will
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@ -274,25 +282,26 @@ We can see how these concepts tie together by disassembling the
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@smallexample
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scheme@@(guile-user)> (define (foo a) (lambda (b) (list foo a b)))
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scheme@@(guile-user)> ,x foo
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Disassembly of #<procedure foo (a)> at #xddb824:
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Disassembly of #<procedure foo (a)> at #xea4ce4:
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0 (assert-nargs-ee/locals 2 0) ;; 2 slots (1 arg) at (unknown file):1:0
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1 (make-closure 1 6 1) ;; anonymous procedure at #xddb840 (1 free var)
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0 (assert-nargs-ee/locals 2 0) ;; 2 slots (1 arg) at (unknown file):1:0
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1 (make-closure 1 7 1) ;; anonymous procedure at #xea4d04 (1 free var)
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4 (free-set! 1 0 0) ;; free var 0
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6 (return 1)
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6 (mov 0 1)
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7 (return-values 2) ;; 1 value
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----------------------------------------
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Disassembly of anonymous procedure at #xddb840:
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Disassembly of anonymous procedure at #xea4d04:
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0 (assert-nargs-ee/locals 2 2) ;; 4 slots (1 arg) at (unknown file):1:16
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1 (toplevel-box 1 73 57 67 #t) ;; `foo'
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0 (assert-nargs-ee/locals 2 2) ;; 4 slots (1 arg) at (unknown file):1:16
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1 (toplevel-box 1 74 58 68 #t) ;; `foo'
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6 (box-ref 1 1)
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7 (make-short-immediate 0 772) ;; () at (unknown file):1:28
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8 (cons 2 2 0)
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9 (free-ref 3 3 0) ;; free var 0
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11 (cons 3 3 2)
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12 (cons 3 1 3)
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13 (return 3)
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12 (cons 2 1 3)
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13 (return-values 2) ;; 1 value
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@end smallexample
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First there's some prelude, where @code{foo} checks that it was called
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@ -115,7 +115,7 @@
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(format port "~aLocal variables:~%" per-line-prefix)
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(for-each
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(lambda (binding)
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(let ((v (frame-binding-ref frame binding)))
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(let ((v (binding-ref binding)))
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(display per-line-prefix port)
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(run-hook before-print-hook v)
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(format port "~a = ~v:@y\n" (binding-name binding) width v)))
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@ -33,10 +33,11 @@
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binding-slot
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binding-representation
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frame-instruction-pointer-or-primitive-procedure-name
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frame-bindings
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frame-lookup-binding
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frame-binding-ref frame-binding-set!
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binding-ref binding-set!
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frame-instruction-pointer-or-primitive-procedure-name
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frame-call-representation
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frame-environment
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frame-object-binding frame-object-name))
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@ -46,8 +47,9 @@
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"scm_init_frames_builtins"))
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(define-record-type <binding>
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(make-binding idx name slot representation)
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(make-binding frame idx name slot representation)
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binding?
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(frame binding-frame)
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(idx binding-index)
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(name binding-name)
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(slot binding-slot)
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@ -206,7 +208,7 @@
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(lp (1+ n) (+ pos (vector-ref parsed n)))))
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killv))
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(define (available-bindings arity ip top-frame?)
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(define (available-bindings frame arity ip top-frame?)
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(let* ((defs (list->vector (arity-definitions arity)))
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(code (arity-code arity))
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(parsed (parse-code code))
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@ -282,7 +284,7 @@
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(if n
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(match (vector-ref defs n)
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(#(name def-offset slot representation)
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(cons (make-binding n name slot representation)
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(cons (make-binding frame n name slot representation)
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(lp (1+ n)))))
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'()))))
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(lp (1+ n) (- offset (vector-ref parsed n)))))))
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@ -292,7 +294,7 @@
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(cond
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((find-program-arity ip)
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=> (lambda (arity)
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(available-bindings arity ip top-frame?)))
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(available-bindings frame arity ip top-frame?)))
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(else '()))))
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(define (frame-lookup-binding frame var)
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@ -304,22 +306,18 @@
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(else
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(lp (cdr bindings))))))
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(define (frame-binding-set! frame var val)
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(let ((binding (if (binding? var)
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var
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(or (frame-lookup-binding frame var)
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(error "variable not bound in frame" var frame)))))
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(frame-local-set! frame (binding-slot binding) val
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(binding-representation binding))))
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(define (frame-binding-ref frame var)
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(let ((binding (if (binding? var)
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var
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(or (frame-lookup-binding frame var)
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(error "variable not bound in frame" var frame)))))
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(frame-local-ref frame (binding-slot binding)
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(binding-representation binding))))
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(define (binding-ref binding)
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(frame-local-ref (or (binding-frame binding)
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(error "binding has no frame" binding))
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(binding-slot binding)
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(binding-representation binding)))
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(define (binding-set! binding val)
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(frame-local-set! (or (binding-frame binding)
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(error "binding has no frame" binding))
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(binding-slot binding)
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val
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(binding-representation binding)))
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(define* (frame-procedure-name frame #:key
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(info (find-program-debug-info
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@ -443,12 +441,13 @@
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=> (lambda (arity)
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(if (and top-frame? (eqv? ip (arity-low-pc arity)))
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(application-arguments)
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(reconstruct-arguments (available-bindings arity ip top-frame?)
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(arity-nreq arity)
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(arity-nopt arity)
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(arity-keyword-args arity)
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(arity-has-rest? arity)
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1))))
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(reconstruct-arguments
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(available-bindings frame arity ip top-frame?)
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(arity-nreq arity)
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(arity-nopt arity)
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(arity-keyword-args arity)
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(arity-has-rest? arity)
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1))))
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((and (primitive-code? ip)
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(program-arguments-alist (frame-local-ref frame 0 'scm) ip))
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=> (lambda (args)
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@ -470,12 +469,12 @@
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(define (frame-environment frame)
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(map (lambda (binding)
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(cons (binding-name binding) (frame-binding-ref frame binding)))
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(cons (binding-name binding) (binding-ref binding)))
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(frame-bindings frame)))
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(define (frame-object-binding frame obj)
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(do ((bs (frame-bindings frame) (cdr bs)))
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((or (null? bs) (eq? obj (frame-binding-ref frame (car bs))))
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((or (null? bs) (eq? obj (binding-ref (car bs))))
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(and (pair? bs) (car bs)))))
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(define (frame-object-name frame obj)
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