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02/04: monads, gexp: Prevent redefinition of syntax parameters.
From: |
guix-commits |
Subject: |
02/04: monads, gexp: Prevent redefinition of syntax parameters. |
Date: |
Wed, 6 Feb 2019 17:06:25 -0500 (EST) |
civodul pushed a commit to branch master
in repository guix.
commit 8245bb74fc7bdcdc2f9d458057cefc9cd982e489
Author: Ludovic Courtès <address@hidden>
Date: Wed Feb 6 21:58:43 2019 +0100
monads, gexp: Prevent redefinition of syntax parameters.
Fixes <https://bugs.gnu.org/27476>.
This fixes multi-threaded compilation of this code where syntax
parameters could end up being redefined and where a race condition could
lead a thread to see the "wrong" value of the syntax parameter.
* guix/monads.scm (define-syntax-parameter-once): New macro.
(>>=, return): Use it.
* guix/gexp.scm (define-syntax-parameter-once): New macro.
(current-imported-modules, current-imported-extensions): Use it.
---
guix/gexp.scm | 15 +++++++++++++--
guix/monads.scm | 15 +++++++++++++--
2 files changed, 26 insertions(+), 4 deletions(-)
diff --git a/guix/gexp.scm b/guix/gexp.scm
index f7c0642..5b5b064 100644
--- a/guix/gexp.scm
+++ b/guix/gexp.scm
@@ -920,7 +920,18 @@ and in the current monad setting (system type, etc.)"
(simple-format #f "~a:~a" line column)))
"<unknown location>")))
-(define-syntax-parameter current-imported-modules
+(define-syntax-rule (define-syntax-parameter-once name proc)
+ ;; Like 'define-syntax-parameter' but ensure the top-level binding for NAME
+ ;; does not get redefined. This works around a race condition in a
+ ;; multi-threaded context with Guile <= 2.2.4: <https://bugs.gnu.org/27476>.
+ (eval-when (load eval expand compile)
+ (define name
+ (if (module-locally-bound? (current-module) 'name)
+ (module-ref (current-module) 'name)
+ (make-syntax-transformer 'name 'syntax-parameter
+ (list proc))))))
+
+(define-syntax-parameter-once current-imported-modules
;; Current list of imported modules.
(identifier-syntax '()))
@@ -931,7 +942,7 @@ environment."
(identifier-syntax modules)))
body ...))
-(define-syntax-parameter current-imported-extensions
+(define-syntax-parameter-once current-imported-extensions
;; Current list of extensions.
(identifier-syntax '()))
diff --git a/guix/monads.scm b/guix/monads.scm
index 6ae616a..6924471 100644
--- a/guix/monads.scm
+++ b/guix/monads.scm
@@ -274,12 +274,23 @@ more optimizations."
(_
#'generic-name))))))))))
-(define-syntax-parameter >>=
+(define-syntax-rule (define-syntax-parameter-once name proc)
+ ;; Like 'define-syntax-parameter' but ensure the top-level binding for NAME
+ ;; does not get redefined. This works around a race condition in a
+ ;; multi-threaded context with Guile <= 2.2.4: <https://bugs.gnu.org/27476>.
+ (eval-when (load eval expand compile)
+ (define name
+ (if (module-locally-bound? (current-module) 'name)
+ (module-ref (current-module) 'name)
+ (make-syntax-transformer 'name 'syntax-parameter
+ (list proc))))))
+
+(define-syntax-parameter-once >>=
;; The name 'bind' is already taken, so we choose this (obscure) symbol.
(lambda (s)
(syntax-violation '>>= ">>= (bind) used outside of 'with-monad'" s)))
-(define-syntax-parameter return
+(define-syntax-parameter-once return
(lambda (s)
(syntax-violation 'return "return used outside of 'with-monad'" s)))