Re: Bug that only happens in ubuntu 22.04 even with older bash version

[Robert E. Griffith]

On 8/10/22 09:26, Chet Ramey wrote:

> On 8/8/22 12:11 PM, Robert E. Griffith wrote:
> > Does anyone know how bash 5.0 and 5.1 on ubuntu 22.04(jammy) could behave
> > differently from bash 5.0 and 5.1 on  20.04(focal)?
> It's probably something in an ubuntu startup file somewhere. Who knows?
> But I get the same results you do using bash-5.1. Here's why.

The difference in the two Ubuntu versions is explained now. I was 
testing like "bash5.x -c <scriptname>" but since my test scripts all 
have shebang lines, it was always running it in the native installed 
bash version so I was not actually testing in other bash versions. Sorry 
for the confusion.

Once I understood the full impact of the 5.1 recursive DEBUG trap 
change, I resolved most of my issues but I have one more that seems like 
a bug introduced in 5.1. When stepping through a non-DEBUG trap with the 
DEBUG trap, BASH_COMMAND does not update until the trap is finished.

   #!/usr/bin/env bash
   echo $BASH_VERSION
   shopt -s extdebug
   function setExitCode() { return $1; }
   function aNoopCommand() { echo "aNoopCommand 1"; }
   trap 'echo USR1: start; aNoopCommand' USR1
   trap 'echo "DBG: $BASH_COMMAND"
        [[ "$BASH_COMMAND" =~ ^aNoopCommand ]] && echo "!!! Hit it"
        setExitCode 0
   ' DEBUG
   kill -USR1 $BASHPID
   echo 1

   [bobg@bgcore-centosS9]$ bin/test51_2.sh
   5.1.8(1)-release
   DBG: kill -USR1 $BASHPID
   DBG: kill -USR1 $BASHPID
   USR1: start
   DBG: kill -USR1 $BASHPID
   DBG: kill -USR1 $BASHPID
   DBG: kill -USR1 $BASHPID
   aNoopCommand 1
   DBG: echo 1
   1

   bobg@ubuntu-focal:$ bin/test51_2.sh
   5.0.17(1)-release
   DBG: kill -USR1 $BASHPID
   DBG: kill -USR1 $BASHPID
   USR1: start
   DBG: aNoopCommand
   !!! Hit it
   DBG: aNoopCommand
   !!! Hit it
   DBG: echo "aNoopCommand 1"
   aNoopCommand 1
   DBG: echo 1
   1

I believe that this script does not make any subshells so its different 
from the other behavior.

In the bash 5.0 run (the second run listed) the BASH_COMMAND is not 
updated for the first simple command in the USR1 trap string but it does 
get updated for the second (and subsequent) simple command and it 
correctly triggers the "!!! Hit it" statement.

In the bash 5.1 run, BASH_COMMAND never updates while the USR1 trap 
string is running and it misses the "!!! Hit it" line.

In 5.1 I can still step through a USR1 trap in my debugger but its very 
confusing because BASH_COMMAND never updates so the debugger code cant 
know which part of the current line is running. In 5.0, the first step 
is messed up but then it corrects itself in the next step.

Is that a deliberate change in 5.1 or is that a bug. (Keeping my fingers 
crossed its a bug:)

--BobG