Re: bash dislikes empty functions or flow control bodies

[Alex fxmbsw7 Ratchev]

as you may see

e() { ; }

and sadly

e() { }

is simply invalid code, as the others say its by posix sh and mr bash wont
digg it i guess

On Tue, Jan 18, 2022, 12:46 <l.bashbug@scarydevilmonastery.net> wrote:

> Configuration Information [Automatically generated, do not change]:
> Machine: x86_64
> OS: linux-gnu
> Compiler: gcc
> Compilation CFLAGS: -g -O2 -fstack-protector-strong -Wformat
> -Werror=format-security -Wall
> uname output: Linux latitude 5.15.0-2-amd64 #1 SMP Debian 5.15.5-2
> (2021-12-18) x86_64 GNU/Linux
> Machine Type: x86_64-pc-linux-gnu
>
> Bash Version: 5.1
> Patch Level: 16
> Release Status: release
>
> Description:
> Even if descriptions of situations where this problem occurs may sound
> contrived, those situation exist and require me to catch this problem
> with additional code:
>    a: defining an empty function will throw a syntax error
>    b: defining an empty bodies flow control construct will thow a syntax
> error
>
> While it may be debatable whether such construct could serve any purpose
> (they actually can), perceived lack of purpose doesn't qualify them as
> syntactically wrong. They aren't. Would they be syntactically wrong,
> the syntax error would continue to exist after adding a harmless
> "no operation" equivalent.
>
> You may justifiable ask "so why not simply use the workaround by adding
> a no operation equivalent" - answer is that it may not be me in person
> creating a function or a flow control construct - the script may do too,
> in accordance with input it received (this is the mentioned part where the
> description may sound contrived, but isn't). Therefore I must protect the
> script at this point from generating empty functions or flow control
> constructs.
>
> You may have guessed here that this is going towards some sort of meta
> programming, and a fuller view of the reason for reporting the bug can be
> obtained at https://github.com/Bushmills/yoda, specifically
> at https://github.com/Bushmills/yoda/issues/7
> Measures to circumvent the problem can be found in file
> https://github.com/Bushmills/yoda/blob/main/yoda at around line 1900
> (at this time) on those lines with text "empty function" in the description
>
>
> Repeat-By:
>         bar() { ; }
>         foo() { if true; then ; fi; }
>         foo() { while :; do ; done; }
>
> Fix:
> In cases where this problem arises, I tend to synthesise the closest
> approximation of a "no operation" I know about, which is ":":
>         bar() { :; }
>         foo() { if true; then :; fi; }
>         foo() { while :; do :; done; }
>
>
>
>
>