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bug#24618: 26.0.50; `condition-case' doesn't allow catching all signals
From: |
Noam Postavsky |
Subject: |
bug#24618: 26.0.50; `condition-case' doesn't allow catching all signals |
Date: |
Mon, 13 Aug 2018 22:38:17 -0400 |
User-agent: |
Gnus/5.13 (Gnus v5.13) Emacs/26.1 (gnu/linux) |
tags 24618 + patch
quit
Philipp Stephani <p.stephani2@gmail.com> writes:
> Consider the following code:
>
> (condition-case err
> (signal 'does-not-exist '(1 2))
> (error (print err)))
>
> The signal is not caught by condition-case because it has no error
> conditions. This makes it impossible to reliably catch all signals
> (without abusing the debugger).
Yeah, I noticed this when I started looking at fixing ert to stop
abusing the debugger like this (Bug#30745 and Bug#11218).
> I propose that an error condition of 't' in `condition-case' should be
> interpreted as 'all conditions'.
Seems easy enough:
>From a18b70875fbcf22009e64bc9d809d1575fba3429 Mon Sep 17 00:00:00 2001
From: Noam Postavsky <npostavs@gmail.com>
Date: Thu, 9 Aug 2018 21:26:30 -0400
Subject: [PATCH] Allow t as a catch-all condition-case handler (Bug#24618)
* src/eval.c (find_handler_clause): Accept a handler of t as always
matching.
(Fcondition_case):
* doc/lispref/control.texi (Handling Errors): Document this.
* etc/NEWS: Announce it.
---
doc/lispref/control.texi | 7 ++++---
etc/NEWS | 3 +++
src/eval.c | 10 ++++++----
3 files changed, 13 insertions(+), 7 deletions(-)
diff --git a/doc/lispref/control.texi b/doc/lispref/control.texi
index 975ab3d075..8a6cf73af5 100644
--- a/doc/lispref/control.texi
+++ b/doc/lispref/control.texi
@@ -1878,9 +1878,10 @@ Handling Errors
Each of the @var{handlers} is a list of the form @code{(@var{conditions}
@var{body}@dots{})}. Here @var{conditions} is an error condition name
to be handled, or a list of condition names (which can include @code{debug}
-to allow the debugger to run before the handler); @var{body} is one or more
-Lisp expressions to be executed when this handler handles an error.
-Here are examples of handlers:
+to allow the debugger to run before the handler). A condition name of
+@code{t} matches any condition. @var{body} is one or more Lisp
+expressions to be executed when this handler handles an error. Here
+are examples of handlers:
@example
@group
diff --git a/etc/NEWS b/etc/NEWS
index 8abbd74e05..f7de6c7295 100644
--- a/etc/NEWS
+++ b/etc/NEWS
@@ -836,6 +836,9 @@ specially; they are now allocated like any other
pseudovector.
* Lisp Changes in Emacs 27.1
+++
+** 'condition-case' now accepts 't' to match any error symbol.
+
++++
** New function 'proper-list-p'.
Given a proper list as argument, this predicate returns its length;
otherwise, it returns nil. 'format-proper-list-p' is now an obsolete
diff --git a/src/eval.c b/src/eval.c
index 8745ba9ef9..8700f0e202 100644
--- a/src/eval.c
+++ b/src/eval.c
@@ -1215,9 +1215,9 @@ DEFUN ("condition-case", Fcondition_case,
Scondition_case, 2, UNEVALLED, 0,
Each element of HANDLERS looks like (CONDITION-NAME BODY...)
where the BODY is made of Lisp expressions.
-A handler is applicable to an error
-if CONDITION-NAME is one of the error's condition names.
-If an error happens, the first applicable handler is run.
+A handler is applicable to an error if CONDITION-NAME is one of the
+error's condition names. A CONDITION-NAME of t applies to any error
+symbol. If an error happens, the first applicable handler is run.
The car of a handler may be a list of condition names instead of a
single condition name; then it handles all of them. If the special
@@ -1854,7 +1854,9 @@ find_handler_clause (Lisp_Object handlers, Lisp_Object
conditions)
for (h = handlers; CONSP (h); h = XCDR (h))
{
Lisp_Object handler = XCAR (h);
- if (!NILP (Fmemq (handler, conditions)))
+ if (!NILP (Fmemq (handler, conditions))
+ /* t is also used as a catch-all by Lisp code. */
+ || EQ (handler, Qt))
return handlers;
}
--
2.11.0
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