On Sun, 10 Mar 2024 23:09:37 +0800
Adrian Ho <lexfi...@gmail.com> wrote:
> [Apologies, an earlier edition of this bug report was sent from the address
> a...@lex.03s.net, which can only be replied to from my internal network.
> Please ignore that report. Thanks much!]
>
> Configuration Information [Automatically generated, do not change]:
> Machine: x86_64
> OS: linux-gnu
> Compiler: gcc-11
> Compilation CFLAGS: -DSSH_SOURCE_BASHRC
> uname output: Linux lex 6.5.0-25-generic #25-Ubuntu SMP PREEMPT_DYNAMIC Wed
> Feb 7 14:58:39 UTC 2024 x86_64 x86_64 x86_64 GNU/Linux
> Machine Type: x86_64-pc-linux-gnu
>
> Bash Version: 5.2
> Patch Level: 26
> Release Status: release
>
> Description:
> "local -g var" incorrectly references a local variable in an
> enclosing scope, while "local -g var=val" correctly references and modifies
> the global variable.
>
> Repeat-By:
> Test script:
>
> #!/usr/bin/env bash
> echo "Bash version: $BASH_VERSION"
>
> b() {
> local -g a=2
> c
> }
> c() {
> local -g a
> a=3
> }
>
> y() {
> local z=1
> x
> }
> x() {
> local -g z=2
> w
> }
> w() {
> local -g z
> echo "w: z=$z"
> z=3
> }
>
> b; y
> echo "a=$a z=$z"
>
> Expected output:
>
> Bash version: 5.2.26(1)-release
> w: z=2
> a=3 z=3
>
> Actual output:
>
> Bash version: 5.2.26(1)-release
> w: z=1
> a=3 z=2
Dynamic scoping can be tremendously confusing. The following examples should
help to clarify the present state of affairs.
$ x() { local a; y; echo "outer: $a"; }
$ y() { local a; a=123; echo "inner: $a"; }
$ x; echo "outermost: $a"
inner: 123
outer:
outermost:
This is likely as you would expect.
$ y() { local -g a; a=123; echo "inner: $a"; }
$ x; echo "outermost: $a"
inner: 123
outer: 123
outermost:
This may not be. There, the effect of the -g option effectively ends at the
outermost scope in which the variable, a, was declared. Namely, that of the x
function.
$ y() { local -g a=123; echo "inner: $a"; }
$ x; echo "outermost: $a"
inner:
outer:
outermost: 123
There, by combining the -g option with assignment syntax, the outermost scope -
that which most would consider as being implied by the term, global - is duly
reached.
The manual states that the "-g option forces variables to be created or
modified at the global scope, even when declare is executed in a shell
function" and that "it is ignored in all other cases". I would consider this
wording insufficient for a user to be able to effectively reason with the
difference between the second case and the other two cases presented.
--
Kerin Millar
