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Re: v4.4 segfault in 'decode_prompt_string' when processing special para


From: Chet Ramey
Subject: Re: v4.4 segfault in 'decode_prompt_string' when processing special parameter
Date: Sat, 21 Jul 2018 19:57:58 -0400
User-agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.13; rv:52.0) Gecko/20100101 Thunderbird/52.9.1

On 7/21/18 2:47 PM, Chris Schoenberg wrote:
> This only works in 4.4; earlier versions throw a 'bad substitution' error. It
> causes an infinite loop of calls between 'expand_prompt_string' and
> 'decode_prompt_string',
> where calls to 'xmalloc' exhaust the heap:
> 
> address@hidden;address@hidden
> 
> I decided to report this because it is not a user-defined recursive
> function and it exhausts the heap rather than the stack.

It's user-defined recursive parameter expansion. A string that undergoes
prompt expansion performs parameter expansion, as documented. If that
parameter expansion passes the same string to prompt expansion, which
performs parameter expansion, you've got user-defined recursion.

-- 
``The lyf so short, the craft so long to lerne.'' - Chaucer
                 ``Ars longa, vita brevis'' - Hippocrates
Chet Ramey, UTech, CWRU    address@hidden    http://tiswww.cwru.edu/~chet/



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