Bug 4243

Summary: hush parsing of ${1+"$@"}
Product: Busybox Reporter: Christian Häggström <christian.haggstrom>
Component: Standard ComplianceAssignee: unassigned
Status: RESOLVED FIXED    
Severity: minor CC: busybox-cvs
Priority: P5    
Version: 1.19.x   
Target Milestone: ---   
Hardware: PC   
OS: Linux   
Host: Target:
Build:
Attachments: adds test for ${1+"$@"}

Description Christian Häggström 2011-09-23 10:24:09 UTC 
Created attachment 3613 [details]
adds test for ${1+"$@"}

We have some shell scripts that needs to be compatible among many shells, and we use ${1+"$@"} instead of "$@" in some wrapper script for the reasons described here:
http://www.gnu.org/s/hello/manual/autoconf/Shell-Substitutions.html

Now, busybox ash and hush both interpret it differenly than bash. I tried with the git HEAD.

$ echo 'for x in ${1+"$@"}; do echo $x; done' > testscript
$ ./hush testscript "a b"
"a
b"
$ bash testscript "a b"
a b

$ ./hush -v
BusyBox v1.20.0.git (2011-09-23 11:11:24 CEST) multi-call binary.

I haven't been able to find what the POSIX standard says about ${1+"$@"}, so please close the bug report if you believe it is non-standard behaviour.
Comment 1 Denys Vlasenko 2012-09-26 09:55:46 UTC 
This is sheer insanity. Bash is buggy wrt """$@", therefore we'll use ambiguous constructs ${1+"$@"}?

Where is the definitive part of the standard which says what exactly should happen with ${1+"$@"} construct?
Comment 2 Mike Frysinger 2012-10-21 17:59:18 UTC 
(In reply to comment #1)

i think it breaks down into two parts.  there's:
  ${1+word}
which, if $1 is set, substitutes the words

then there's "$@" which expands the array of words.

so it should be:
$ set -- '1 2' 3 4
$ printf '%s\n' "$@"
1 2
3
4

you could e-mail austin-group-l@opengroup.org for an interpretation ... i'm sure someone will be able to get the details for you
Comment 3 Denys Vlasenko 2018-08-04 20:31:17 UTC 
Fixed in git.