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commit d79a226359d28f4a1dc5df136e5544d699903a96
Author: Rob Browning <rlb@defaultvalue.org>
Date: Sat Jul 3 14:01:12 2021 -0500
Fix crash on #nil in syntaxes
In 3.0.7 (after 0cc799185576712d69f11fc794454f2f5447bef7 "Ensure
that (syntax ()) results in ("), the use of #nil in syntax-rules
expansions like this:
(define-syntax foo
(syntax-rules ()
((_ x) (eq? #nil x))))
(foo #t)
could cause a crash that looks like this:
ice-9/psyntax.scm:2795:12: In procedure syntax-violation:
Syntax error:
unknown location: unexpected syntax in form ()
To fix it, add another special case (the commit mentioned above
special-cased the empty list) to preserve #nil
* module/ice-9/psyntax.scm (gen-syntax): Preserve #nil.
* test-suite/tests/syntax.test: Test #nil in syntax expansions.
Closes: 49305
diff --git a/module/ice-9/psyntax.scm b/module/ice-9/psyntax.scm
index 663d9275a..bd4bd6723 100644
--- a/module/ice-9/psyntax.scm
+++ b/module/ice-9/psyntax.scm
@@ -2157,6 +2157,7 @@
(lambda ()
(gen-syntax src #'(e1 e2 ...) r maps ellipsis? mod))
(lambda (e maps) (values (gen-vector e) maps))))
+ (x (eq? (syntax->datum #'x) #nil) (values '(quote #nil) maps))
(() (values '(quote ()) maps))
(_ (values `(quote ,e) maps))))))
diff --git a/test-suite/tests/syntax.test b/test-suite/tests/syntax.test
index a2999ac43..510e7104d 100644
--- a/test-suite/tests/syntax.test
+++ b/test-suite/tests/syntax.test
@@ -1684,6 +1684,16 @@
(hash interpreted most-positive-fixnum)
(hash compiled most-positive-fixnum))))
+(with-test-prefix "#nil in syntaxes"
+ (pass-if-equal "does not crash"
+ 42
+ (let ()
+ (define-syntax foo
+ (syntax-rules ()
+ ;; In 3.0.7 this would crash with
+ ;; unknown location: unexpected syntax in form ()
+ ((_ x) (when (eq? x #nil) 42))))
+ (foo #nil))))
;;; Local Variables:
;;; eval: (put 'pass-if-syntax-error 'scheme-indent-function 1)
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