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From: | 杨圣 |
Subject: | bug#31995: 26.1; Condition-case failed to catch error |
Date: | Wed, 11 Jul 2018 22:46:21 -0700 |
User-agent: | Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.8.0 |
condition-case was able to catch C
stack overflow before commit f0a1e9ec. I understand that
recovering from C stack overflow is magical and can be tricky, but
emacs is capable of this thanks to all of your efforts. The only
part missing is re-throwing this as a lisp exception, which should
not be as hard as recovering from C stack overflow.
Here is why this feature can be important. When we open a file, find-file-hook will call many functions, including but not limited to undo-tree. These functions read additional files (undo-tree, project file, dir-local, etc.) and perform tasks. To guard against file corruption and other problems, all reads are wrapped in some try-catch clause. However, the trust in these try-catch clauses are let down, and a single file corruption (or a file that can cause C stack overflow) ruins the whole process of loading file with a mysterious message of"Recovered from C stack overflow". I don't think this is acceptable. From a lisp programmer's perspective, if exceptions should occur, they should be caught. This is exactly the behavior that condition-case and other try-catch clause promise. I am not an expert in C, debugging the C part of emacs can be painful for me. Therefore I bisected and found the offending commits (see my original bug report). Hope this can help you pin point the problem and fix the bug. On 07/11/2018 02:48 PM, Noam Postavsky wrote: retitle 31995 Condition-case can't catch C stack overflow tags 31995 + wontfix quit Sheng Yang (杨圣) <yangsheng6810@gmail.com> writes:It seems that the function call ~(read (current-buffer))~ causes C stack overflow. Though I personally believe the undo-tree file is not corrupted, I assume this error should be caught by condition-case even if the file to read is indeed corrupted.The file is not corrupted, it's just that the recursion goes too deep during reading. However, I don't think condition-case can reasonably catch C stack overflow. As it is, recovering from C stack overflow at all is a bit controversial, which is why we have the attempt-stack-overflow-recovery variable which you can set to nil in order to reliably segfault instead. -- Sheng Yang(杨圣) PhD student Computer Science Department University of Maryland, College Park E-mail:yangsheng6810@gmail.com |
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