LyX 2.4 -- memory full when trying to copy a math block having boxed expression with 4 levels of nested deep subscript

[Alexander Dunlap]

On Sat, May 18, 2024, at 9:52 AM, Alexander Dunlap wrote:
> On Sat, May 18, 2024, at 2:30 AM, Niranjana K M wrote:
>> Dear LyX developers,
>>     Thank you and congratulations for heading towards much awaited LyX-2.4.
>> I have been using LyX-2.4-RC1 from last 6 months and yesterday accidentally i caught this strange behavior. And I even installed recently released LyX-2.4 and the behavior persisted in this version also. But i am not facing this problem in LyX-2.3.7.
>>     The problem is, when I try to copy, by selecting and pressing Ctrl+C (or Copy from edit menu), a math block which is boxed and also having deep nested subscripts to at least 4 levels then my computer memory rapidly got consumed to the full (starting from 1GB to ~10GB) and in the end LyX closed with following message.
>> 
>> $ /usr/local/bin/lyx
>> Error: Software exception Detected
>> ----------------------------------------
>> LyX has caught an exception, it will now attempt to save all unsaved documents and exit.
>> Exception: std::bad_alloc
>> Aborted
>> 
>> Following is the math block which caused it, (LyX code)
>> \begin_inset Formula 
>> \[
>> \boxed{v=\left[v_{p}\right]_{a_{0}}}
>> \]
>> \end_inset
>> 
>> The file is also attached in the end and here is the screenshot of the math block.
>> Screenshot from 2024-05-18 11-43-00.png
>> 
>> It is a legitimate construction and it gives no problem in LyX-2.3.7 (confirmed).
>> If either the box is removed or the subscript 0 is removed from *a*, then it has no issues in copying.
>> 
>> All these versions I mentioned were compiled from source on Gentoo Linux. This LyX-2.4 was compiled with the following configuration,
>> $ ./configure --without-included-boost
>> Configuration
>>   Host type:               x86_64-pc-linux-gnu
>>   Special build flags:      build=release callback-printing use-hunspell use-aspell use-enchant
>>   Bundled libraries:        nod
>>   C++ Compiler:            g++ (13.2.1)
>>   C++ Compiler flags:       -fPIC -O2 -std=c++17 
>>   C++ Compiler user flags:   -std=c++17  -march=native -O2 -pipe
>>   Linker flags:             -rdynamic
>>   Linker user flags:       
>>   Qt Frontend:
>>       Qt version:   5.15.11
>>   Packaging:               posix
>>   LyX binary dir:          /usr/local/bin
>>   LyX files dir:           /usr/local/share/lyx
>> 
>> I loved the new features in LyX-2.4 and don't want to go back to LyX-2.3.7 due to this issue. Please help in this regard.
> 
> I can reproduce this. I investigated a little and it seems that the problem is that the "while (true)" loop in the splitAndWrapInMText function in InsetMathBox.cpp is never terminating. I believe that the reason for this is that the logic in this function is not correctly identifying the matching XHTML end tag for a given start tag, since it doesn't take into account nested tags properly.

Here is a patch that fixes the problem for me. It needs extensive checking/testing though because I do not know too much about XHTML or what all sorts of input might be seen in this function.

> 
> 
>> 
>> *Regards*
>> *Niranjana*
>> -- 
>> lyx-devel mailing list
>> lyx-devel at lists.lyx.org
>> http://lists.lyx.org/mailman/listinfo/lyx-devel
>> 
>> 
>> *Attachments:*
>>  • test.24.lyx
> 
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