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Re: RETURN trap will inherit last RETURN trap cmd though set +T


From: Shen Herbert
Subject: Re: RETURN trap will inherit last RETURN trap cmd though set +T
Date: Thu, 24 Jan 2019 11:04:16 +0000

On 2019-01-23 15:20, Chet Ramey wrote:
> On 1/23/19 10:59 AM, Shen Herbert wrote:
> > Configuration Information [Automatically generated, do not change]:
> > Machine: x86_64
> > OS: linux-gnu
> > Compiler: gcc
> > Compilation CFLAGS: -march=x86-64 -mtune=generic -O2 -pipe 
> > -fstack-protector-strong -fno-plt 
> > -DDEFAULT_PATH_VALUE='/usr/local/sbin:/usr/local/bin:/usr/bin' 
> > -DSTANDARD_UTILS_PATH='/usr/bin' -DSYS_BASHRC='/etc/bash.bashrc' 
> > -DSYS_BASH_LOGOUT='/etc/bash.bash_logout' -DNON_INTERACTIVE_LOGIN_SHELLS 
> > -Wno-parentheses -Wno-format-security
> > uname output: Linux arch.ishbguy.org 4.20.3-arch1-1-ARCH #1 SMP PREEMPT Wed 
> > Jan 16 22:38:58 UTC 2019 x86_64 GNU/Linux
> > Machine Type: x86_64-pc-linux-gnu
> > 
> > Bash Version: 5.0
> > Patch Level: 0
> > Release Status: release
> > 
> > Description:
> > 
> > RETURN trap will inherit last RETURN trap cmd though set +T under bash 5.0 
> > or bash 4.4, however, this will not happen under bash 4.3. For example:
> > ```
> > set +T
> > one { trap 'echo in one' RETURN; }
> > all {
> >     trap 'echo in all' RETURN
> >     one
> > }
> > all
> > ```
> > in bash 5.0 and 4.4 will print:
> > ```
> > in one
> > in one
> > ```
> > in bash 4.3 will print:
> > ```
> > in one
> > in all
> > ```
> 
> There is only a single RETURN trap; traps are not local. If a called
> function sets the RETURN trap, it should overwrite the caller's trap,
> and the caller's value should not get restored. Then, when the caller
> returns, and there is a RETURN trap set, it should execute the current
> RETURN trap, not the one it had before it called the second function
> (`one' in this case).
> 
> The behavior of bash-4.3 was a bug. I changed it partly as the result of
> this bug report:
> 
> http://lists.gnu.org/archive/html/bug-bash/2015-08/msg00130.html
> 
> This change made the behavior of the RETURN trap align with the DEBUG and
> ERROR traps.
> 
> Chet
> -- 
> ``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/

OK, I got it. Thank you very much.

-- 
------------------------------------------
Herbert Shen
Mail: address@hidden
GitHub: https://github.com/ishbguy
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