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[Emacs-diffs] emacs-26 3f4b8e9: * src/data.c (Fmake_local_variable): Fix
From: |
Stefan Monnier |
Subject: |
[Emacs-diffs] emacs-26 3f4b8e9: * src/data.c (Fmake_local_variable): Fix bug#34318 |
Date: |
Tue, 12 Feb 2019 16:33:30 -0500 (EST) |
branch: emacs-26
commit 3f4b8e9a299f88a8ea11c0ea6a281a34852e541a
Author: Stefan Monnier <address@hidden>
Commit: Stefan Monnier <address@hidden>
* src/data.c (Fmake_local_variable): Fix bug#34318
Revert part of ed962f2b8a.
* test/src/data-tests.el (data-tests-make-local-forwarded-var):
Add corresponding test.
---
src/data.c | 10 ++++++++++
test/src/data-tests.el | 18 ++++++++++++++++++
2 files changed, 28 insertions(+)
diff --git a/src/data.c b/src/data.c
index 5711148..ed6dedb 100644
--- a/src/data.c
+++ b/src/data.c
@@ -1954,6 +1954,16 @@ Instead, use `add-hook' and specify t for the LOCAL
argument. */)
(current_buffer,
Fcons (Fcons (variable, XCDR (blv->defcell)),
BVAR (current_buffer, local_var_alist)));
+
+ /* If the symbol forwards into a C variable, then load the binding
+ for this buffer now, to preserve the invariant that forwarded
+ variables must always hold the value corresponding to the
+ current buffer (they are swapped eagerly).
+ Otherwise, if C code modifies the variable before we load the
+ binding in, then that new value would clobber the default binding
+ the next time we unload it. See bug#34318. */
+ if (blv->fwd)
+ swap_in_symval_forwarding (sym, blv);
}
return variable;
diff --git a/test/src/data-tests.el b/test/src/data-tests.el
index 0069ee8..f3b4262 100644
--- a/test/src/data-tests.el
+++ b/test/src/data-tests.el
@@ -508,4 +508,22 @@ comparing the subr with a much slower lisp implementation."
(bound-and-true-p data-tests-foo2)
(bound-and-true-p data-tests-foo3)))))))
+(ert-deftest data-tests-make-local-forwarded-var () ;bug#34318
+ ;; Boy, this bug is tricky to trigger. You need to:
+ ;; - call make-local-variable on a forwarded var (i.e. one that
+ ;; has a corresponding C var linked via DEFVAR_(LISP|INT|BOOL))
+ ;; - cause the C code to modify this variable from the C side of the
+ ;; forwarding, but this needs to happen before the var is accessed
+ ;; from the Lisp side and before we switch to another buffer.
+ ;; The trigger in bug#34318 doesn't exist any more because the C code has
+ ;; changes. Instead I found the trigger below.
+ (with-temp-buffer
+ (setq last-coding-system-used 'bug34318)
+ (make-local-variable 'last-coding-system-used)
+ ;; This should set last-coding-system-used to `no-conversion'.
+ (decode-coding-string "hello" nil)
+ (should (equal (list last-coding-system-used
+ (default-value 'last-coding-system-used))
+ '(no-conversion bug34318)))))
+
;;; data-tests.el ends here
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Stefan Monnier <=