Re: [sr #108491] Is `set -o histexpand` meant to trump `set -o posix`? [eg, echo "#!/"] (Because it does.)

[Geoff Nixon]

So having done some more playing around with this, I've found that when 
bash is configured and compiled with '--enable-strict-posix-default', 
this doesn't occur.  I see this is documented in the change log for 
4.3alpha, as:

  k.  When compiled for strict Posix conformance, history expansion is 
disabled by default.

But why is this a compile-time-only behavior?

There's nothing else in the documentation about any differences between 
bash compiled with -DSTRICT_POSIX v.s. enabling this mode with `bash 
--posix`. It just says that POSIX mode will become a default option. 
And reverse also seems to be true; if you compile with -DSTRICT_POSIX, 
invoke the shell, then 'set +o posix', history expansion remains 
disabled? This definitely seems like it could cause some trouble.

URL: http://savannah.gnu.org/support/?108491

Summary: Is `set -o histexpand` meant to trump `set -o posix`? [eg, 
echo "#!/"] (Because it does.)
                Project: The GNU Bourne-Again SHell
                Submitted by: None
                Submitted on: Sat 01 Feb 2014 01:32:34 PM UTC
                Category: None
                Priority: 5 - Normal
                Severity: 5 - Blocker
                Status: None
                Privacy: Public
                Assigned to: None
                Originator Email: geoff.nixon@aol.com
                Open/Closed: Open
                Discussion Lock: Any
                Operating System: *BSD

   _______________________________________________________

Details:

From: geoff.nixon@aol.com
To:  chet@po.cwru.edu, chet.ramey@case.edu, 
chet@cwru.edu,bash-testers@case.edu, bash-testers@cwru.edu

Subject: Is `set -o histexpand` meant to trump `set -o posix`? [eg, 
echo "#!/"] (It does.)

Configuration Information [Automatically generated, do not change]:
Machine: x86_64
OS: darwin13.1.0
Compiler: /usr/bin/clang
Compilation CFLAGS:  -DPROGRAM='bash' -DCONF_HOSTTYPE='x86_64'
-DCONF_OSTYPE='darwin13.1.0' 
-DCONF_MACHTYPE='x86_64-apple-darwin13.1.0' -DCONF_VENDOR='apple'
-DLOCALEDIR='/Users/Shared/usr/local/opt/bash/share/locale' 
-DPACKAGE='bash'
-DSHELL -DHAVE_CONFIG_H -DMACOSX -DDEBUG -DMALLOC_DEBUG -I.  -I. 
-I./include -I./lib -g -O2
uname output: Darwin air.local 13.1.0 Darwin Kernel Version 13.1.0: Thu 
Jan 16
19:40:37 PST 2014; root:xnu-2422.90.20~2/RELEASE_X86_64 x86_64
Machine Type: x86_64-apple-darwin13.1.0

Bash Version: 4.3
Patch Level: 0
Release Status: rc2

Description:

Please see these:

 
http://stackoverflow.com/questions/21494213/why-cant-i-echo-the-characters-in-a-string-in-bash
http://stackoverflow.com/questions/21496049/what-is-the-intended-effective-ordering-of-set-o-options-in-bash-does-histe

Its still not at all clear to me if I'm correct or not; and I kind of 
got a
serious beatdown for calling it a bug on Stack Overflow. So I'm not 
sure if
this is a 'blocker' per se or even something you'll consider a bug. But 
it
certainly blocks me from wanting to using bash to execute a 
POSIX-portable
script!

(Note that I now fully realize my statement there to the effect of 
'bash never
sees any updates so use a different shell' is erroneous. I made this 
claim
because a keep a git checkout on my hard drive which gets pulled daily 
- but
your master branch is configured to track 4.2 rather than devel, so 
that's
what I thought was indeed the case. I was completely aghast to find 
that 4.3
is in rc2 having just made that statement, and I intend to redact it a 
soon as
there's some resolution to this "bug", be it a bug or not.)

I apologize if this appears in your inbox two dozen times. I don't know 
if
sendmail even works at all on my system; and there are three slightly
different emails in the bashbug script, in git, and the top hit in a web
search for your name. I'm trying to make sure this gets seen before the
'release' button gets pushed for 4.3.

Repeat-By:
        set -o histexpand && set -o posix && echo "#!/"
       set -o histexpand && set -o posix && echo "#!/bin/bash"
        echo $?

Fix:
        Disable `set -o histexpand` while parsing and expanding double-quoted
        strings, at least for lines which begin with a hash symbol, 
when `set -o posix` is set.

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 <http://savannah.gnu.org/support/?108491>