[vim] Trying to dump deeply nested list with jsonencode() crashes (#588)

[Nikolai Aleksandrovich Pavlov]

Consider the following code:

vim -u NONE --cmd 'let l=[]' --cmd 'call map(range(1024*1024), "extend(g:, {\"l\": [g:l]})")' --cmd 'echo jsonencode(l)'

This crashes with stack full of json_encode_item() calls.

One may be interested in code from neovim/neovim#3365 because it is not using recursion for dumping values.

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[Bram Moolenaar]

Nikolai Pavlov wrote:

> Consider the following code:
>
> vim -u NONE --cmd 'let l=[]' --cmd 'call map(range(1024*1024), "extend(g:, {\"l\": [g:l]})")' --cmd 'echo jsonencode(l)'
>
> This crashes with stack full of json_encode_item() calls.
>
> One may be interested in code from neovim/neovim#3365 because it is
> not using recursion for dumping values.

The current implementation wasn't really made for large JSON files.
But if someone makes a patch it might get included.
Besides the recursiveness, using the growarray probably also is quite
inefficient. list_join_inner() has a better solution, but it takes
quite a bit of code.

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[Nikolay Aleksandrovich Pavlov]

2016-01-24 19:53 GMT+03:00 Bram Moolenaar <vim-dev...@256bit.org>:

Nikolai Pavlov wrote:

> Consider the following code:
>
> vim -u NONE --cmd 'let l=[]' --cmd 'call map(range(1024*1024), "extend(g:, {\"l\": [g:l]})")' --cmd 'echo jsonencode(l)'
>
> This crashes with stack full of json_encode_item() calls.
>
> One may be interested in code from neovim/neovim#3365 because it is
> not using recursion for dumping values.

The current implementation wasn't really made for large JSON files.
But if someone makes a patch it might get included.
Besides the recursiveness, using the growarray probably also is quite
inefficient. list_join_inner() has a better solution, but it takes
quite a bit of code.

If one takes implementation from Neovim it is not a problem to make it first compute length and then dump. The problem is that json_encode_item should have at least stack overflow protection common for other recursive calls: I mean, a counter.

 

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/// sponsor Vim, vote for features -- http://www.Vim.org/sponsor/ \\\
\\\ an exciting new programming language -- http://www.Zimbu.org ///
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[Christian Brabandt]

Closed #588 as completed via abd2d7d.

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