Here is another seg faulting example.
example3a.rkt:
#lang racket
(require (for-syntax syntax/parse))
(provide test)
(define-syntax test
(syntax-parser
[_
#:with lam+
(local-expand
#'(λ (z) (let-syntax ([z (make-rename-transformer #'z)]) z))
'expression null)
#'(define-syntax x #'lam+)]))
(test)
example3b.rkt:
#lang racket
(require "example3a.rkt")
To reproduce:
1) Open example3b.rkt in drracket and run. It may or may not crash
with a seg fault.
2) Delete compiled directory and run again.
Observations:
- A crash typically occurs after repeating the steps 2-3 times but
sometimes I have to run-and-compile 5 or more times.
- The provide appears to be necessary to cause the crash, even though
it's unused in the second file.
- I'm not sure which parts of the macro are actually needed to create
the crash but the local-expand and define-syntax seem to be involved.
On Tue, Jul 21, 2015 at 3:39 PM, Stephen Chang <[email protected]> wrote:
>> Repair pushed. The problem was related to the bytecode format, so I
>> had to bump the version number.
>
> Ah ok. This makes sense because I occasionally could not reproduce the
> crash unless I forced a recompile. Sorry, I should have mentioned this
> initially. Thanks.
>
>>
>> Thanks!
>>
>> At Tue, 21 Jul 2015 13:27:14 -0400, Stephen Chang wrote:
>>> The previous example now works. Thanks.
>>>
>>> But here is a variation that still seg faults:
>>>
>>> file1.rkt:
>>>
>>> #lang racket
>>> (require (for-syntax syntax/parse))
>>> (provide (rename-out [my-define define]))
>>> (define-syntax my-define
>>> (syntax-parser
>>> [(_ x:id e)
>>> ;; undef is unbound identifier
>>> #:with y (local-expand #'undef 'expression null)
>>> #'(void)]))
>>>
>>> ; (my-define X 1) produces: "undef: unbound identifier in module in: undef"
>>>
>>> file2.rkt
>>>
>>> #lang racket
>>> (require "file1.rkt")
>>> (define X 1)
>>>
>>> Running file2.rkt in drracket with the new expander crashes drracket with:
>>>
>>> SIGSEGV MAPERR si_code 1 fault on addr 0x20
>>> Aborted
>>>
>>> On Mon, Jul 20, 2015 at 3:49 PM, Matthew Flatt <[email protected]> wrote:
>>> > I've just pushed a repair for this bug. Thanks for the report!
>>> >
>>> >
>>> >
>>> >> On Jul 20, 2015, at 12:47 PM, Stephen Chang <[email protected]> wrote:
>>> >>
>>> >> The following code produces a seg fault with the new expander (today's
>>> >> build) in the scenario described below:
>>> >>
>>> >> file1.rkt:
>>> >>
>>> >> #lang racket
>>> >> (require (for-syntax syntax/parse))
>>> >>
>>> >> (define-syntax (define-constructor stx)
>>> >> (syntax-parse stx
>>> >> [(_ X:id)
>>> >> #'(define-syntax X
>>> >> (syntax-parser
>>> >> [(_ x (... ...)) #'(void x (... ...))]))]))
>>> >>
>>> >> (define-constructor C)
>>> >>
>>> >> (define-syntax define-alias
>>> >> (syntax-parser
>>> >> [(_ alias:id e)
>>> >> #:with e+ (local-expand #'e 'expression null)
>>> >> #'(define-syntax alias
>>> >> (syntax-parser [x:id #'e+]))]))
>>> >>
>>> >> (define-alias D (C 1))
>>> >>
>>> >> file2.rkt:
>>> >> (require "file1.rkt")
>>> >>
>>> >> A few notes:
>>> >> - running file2.rkt in DrRacket with the new expander crashes drracket
>>> >> with the error:
>>> >>
>>> >> SIGSEGV MAPERR si_code 1 fault on addr (nil)
>>> >> Aborted
>>> >>
>>> >> - running file2.rkt with racket (new expander) produces no error
>>> >> - running file2.rkt produced no error with the old expander
>>> >> - running file1.rkt with either racket or drracket, new expander or
>>> >> old expander, produces no error
>>> >>
>>> >> I'm not completely caught up with the new expander threads so
>>> >> apologies in advance if someone has already raised this issue.
>>> >>
>>> >> --
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>>> >>
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