Bug#1016919: lintian: bash-term-in-posix-shell false positive for `. "$(dirname "$0")/functions.sh"`

Gioele Barabucci

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Aug 9, 2022, 3:30:03 PM8/9/22

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Package: lintian
Version: 2.115.2

The following script (approved by `shellcheck -s sh`) causes a false
positive warning `bash-term-in-posix-shell`:

#!/bin/sh
. "$(dirname "$0")/functions.sh"
do_something

I: my-test: bash-term-in-posix-shell '. "$(dirname "$0")/functions.sh"'
[usr/bin/my-test:2]

Probably the lintian check is misparsing the quotes and the space
between `dirname` and `"$0"`, leading it to believe that an argument is
being passed to the sourced script (that would be, in fact, a bashism).

Regards,

--
Gioele Barabucci

Diederik de Haas

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Jan 31, 2023, 11:30:04 AM1/31/23

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Package: lintian
Version: 2.116.2
Followup-For: Bug #1016919

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While inspecting lintian's output wrt (several) kernel builds I did, I
found the following warning, which seems to be a false positive?

I: linux-perf: bash-term-in-posix-shell '. $(dirname $0)/../lib/coresight.sh' [usr/lib/perf-core/tests/shell/coresight/asm_pure_loop.sh:8]
I: linux-perf: bash-term-in-posix-shell '. $(dirname $0)/../lib/coresight.sh' [usr/lib/perf-core/tests/shell/coresight/memcpy_thread_16k_10.sh:8]
I: linux-perf: bash-term-in-posix-shell '. $(dirname $0)/../lib/coresight.sh' [usr/lib/perf-core/tests/shell/coresight/thread_loop_check_tid_10.sh:8]
I: linux-perf: bash-term-in-posix-shell '. $(dirname $0)/../lib/coresight.sh' [usr/lib/perf-core/tests/shell/coresight/thread_loop_check_tid_2.sh:8]
I: linux-perf: bash-term-in-posix-shell '. $(dirname $0)/../lib/coresight.sh' [usr/lib/perf-core/tests/shell/coresight/unroll_loop_thread_10.sh:8]
I: linux-perf: bash-term-in-posix-shell '. $(dirname $0)/lib/probe.sh' [usr/lib/perf-core/tests/shell/probe_vfs_getname.sh:7]
I: linux-perf: bash-term-in-posix-shell '. $(dirname $0)/lib/probe.sh' [usr/lib/perf-core/tests/shell/record+probe_libc_inet_pton.sh:13]
I: linux-perf: bash-term-in-posix-shell '. $(dirname $0)/lib/probe.sh' [usr/lib/perf-core/tests/shell/record+script_probe_vfs_getname.sh:12]
I: linux-perf: bash-term-in-posix-shell '. $(dirname $0)/lib/probe.sh' [usr/lib/perf-core/tests/shell/trace+probe_vfs_getname.sh:13]
I: linux-perf: bash-term-in-posix-shell '. $(dirname $0)/lib/probe_vfs_getname.sh' [usr/lib/perf-core/tests/shell/probe_vfs_getname.sh:11]
I: linux-perf: bash-term-in-posix-shell '. $(dirname $0)/lib/probe_vfs_getname.sh' [usr/lib/perf-core/tests/shell/record+script_probe_vfs_getname.sh:16]
I: linux-perf: bash-term-in-posix-shell '. $(dirname $0)/lib/probe_vfs_getname.sh' [usr/lib/perf-core/tests/shell/trace+probe_vfs_getname.sh:18]

Looking at the first item:
```sh
$ cat tools/perf/tests/shell/coresight/asm_pure_loop.sh
#!/bin/sh -e
# CoreSight / ASM Pure Loop

# SPDX-License-Identifier: GPL-2.0
# Carsten Haitzler <carsten....@arm.com>, 2021

TEST="asm_pure_loop"
. $(dirname $0)/../lib/coresight.sh
ARGS=""
DATV="out"
DATA="$DATD/perf-$TEST-$DATV.data"

perf record $PERFRECOPT -o "$DATA" "$BIN" $ARGS

perf_dump_aux_verify "$DATA" 10 10 10

err=$?
exit $err
```

Shellcheck does not flag this as having bashisms.
Searching for both `.` and `dirname` and they both seem to be POSIX compliant.
https://unix.stackexchange.com/a/253527
https://unix.stackexchange.com/a/17885

Which leads me to believe this is a false positive indeed.

- -- System Information:
Debian Release: bookworm/sid
APT prefers testing
APT policy: (990, 'testing'), (500, 'unstable'), (101, 'experimental')
Architecture: amd64 (x86_64)

Kernel: Linux 6.1.0-2-amd64 (SMP w/4 CPU threads; PREEMPT)
Locale: LANG=en_US.UTF-8, LC_CTYPE=en_US.UTF-8 (charmap=UTF-8), LANGUAGE=en_US:en
Shell: /bin/sh linked to /usr/bin/dash
Init: systemd (via /run/systemd/system)
LSM: AppArmor: enabled

Versions of packages lintian depends on:
ii binutils 2.40-2
ii bzip2 1.0.8-5+b1
ii diffstat 1.65-1
ii dpkg 1.21.19
ii dpkg-dev 1.21.19
ii file 1:5.44-3
ii gettext 0.21-10
ii gpg 2.2.40-1
ii intltool-debian 0.35.0+20060710.6
ii iso-codes 4.12.0-1
ii libapt-pkg-perl 0.1.40+b2
ii libarchive-zip-perl 1.68-1
ii libberkeleydb-perl 0.64-2+b1
ii libcapture-tiny-perl 0.48-2
ii libclass-xsaccessor-perl 1.19-4+b1
ii libclone-perl 0.46-1
ii libconfig-tiny-perl 2.28-2
ii libconst-fast-perl 0.014-2
ii libcpanel-json-xs-perl 4.32-1+b1
ii libdata-dpath-perl 0.58-2
ii libdata-validate-domain-perl 0.10-1.1
ii libdata-validate-uri-perl 0.07-2
ii libdevel-size-perl 0.83-2+b1
pn libdigest-sha-perl <none>
ii libdpkg-perl 1.21.19
ii libemail-address-xs-perl 1.05-1+b1
ii libfile-basedir-perl 0.09-2
ii libfile-find-rule-perl 0.34-3
ii libfont-ttf-perl 1.06-2
ii libhtml-html5-entities-perl 0.004-3
ii libhtml-tokeparser-simple-perl 3.16-4
ii libio-interactive-perl 1.023-2
ii libipc-run3-perl 0.048-3
ii libjson-maybexs-perl 1.004004-1
ii liblist-compare-perl 0.55-2
ii liblist-someutils-perl 0.59-1
ii liblist-utilsby-perl 0.12-2
ii libmldbm-perl 2.05-4
ii libmoo-perl 2.005005-1
ii libmoox-aliases-perl 0.001006-2
ii libnamespace-clean-perl 0.27-2
ii libpath-tiny-perl 0.144-1
ii libperlio-gzip-perl 0.20-1+b1
ii libperlio-utf8-strict-perl 0.010-1
ii libproc-processtable-perl 0.634-1+b2
ii libregexp-wildcards-perl 1.05-3
ii libsereal-decoder-perl 5.001+ds-1+b1
ii libsereal-encoder-perl 5.001+ds-2
ii libsort-versions-perl 1.62-3
ii libsyntax-keyword-try-perl 0.28-1
ii libterm-readkey-perl 2.38-2+b1
ii libtext-levenshteinxs-perl 0.03-5+b1
ii libtext-markdown-discount-perl 0.16-1
ii libtext-xslate-perl 3.5.9-1+b2
ii libtime-duration-perl 1.21-2
ii libtime-moment-perl 0.44-2+b1
ii libtimedate-perl 2.3300-2
ii libunicode-utf8-perl 0.62-2
ii liburi-perl 5.17-1
ii libwww-mechanize-perl 2.15-1
ii libwww-perl 6.67-1
ii libxml-libxml-perl 2.0207+dfsg+really+2.0134-1+b1
ii libyaml-libyaml-perl 0.84+ds-1+b1
ii lzip [lzip-decompressor] 1.23-4
ii lzop 1.04-2
ii man-db 2.11.2-1
ii patchutils 0.4.2-1
ii perl [libencode-perl] 5.36.0-7
ii t1utils 1.41-4
ii unzip 6.0-27
ii xz-utils 5.4.1-0.0

lintian recommends no packages.

Versions of packages lintian suggests:
pn binutils-multiarch <none>
pn libtext-template-perl <none>

- -- no debconf information

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Russ Allbery

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Jan 31, 2023, 12:20:04 PM1/31/23

to

Diederik de Haas <didi....@cknow.org> writes:

> While inspecting lintian's output wrt (several) kernel builds I did, I
> found the following warning, which seems to be a false positive?

> I: linux-perf: bash-term-in-posix-shell '. $(dirname $0)/../lib/coresight.sh' [usr/lib/perf-core/tests/shell/coresight/asm_pure_loop.sh:8]

Yeah, I think it's a false positive in this check (check_line in
Lintian::Check::Shell::NonPosix::BashCentric):

# since this test is ugly, I have to do it by itself
# detect source (.) trying to pass args to the command it runs
# The first expression weeds out '. "foo bar"'
if (
$line !~ m{\A \s*\.\s+
(?:\"[^\"]+\"|\'[^\']+\')\s*
(?:[\&\|<;]|\d?>|\Z)}xsm
&& $line =~ /^\s*(\.\s+[^\s;\`:]+\s+([^\s;]+))/
) {

my ($dot_command, $extra) = ($1, $2);

push(@matches, $dot_command)
if length $dot_command
&& $extra !~ m{^ & | [|] | < | \d? > }x;
}

It's picking up the space in $(dirname $0) and thinking that's a space in
the . command line and therefore arguments are being passed to the sourced
file, which is a bashism. The missing logic is understanding that a $()
block is effectively a quoted string and thus should be ignored for the
purposes of this test.

--
Russ Allbery (r...@debian.org) <https://www.eyrie.org/~eagle/>

Diederik de Haas

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Jan 31, 2023, 4:30:05 PM1/31/23

to

On Tuesday, 31 January 2023 18:10:57 CET Russ Allbery wrote:
> > I: linux-perf: bash-term-in-posix-shell '. $(dirname
> > $0)/../lib/coresight.sh'
> > [usr/lib/perf-core/tests/shell/coresight/asm_pure_loop.sh:8]
> Yeah, I think it's a false positive in this check (check_line in
> Lintian::Check::Shell::NonPosix::BashCentric):

I looked a little deeper/further and specifically into `lib/coresight.sh` and
that file does contain `echo -n`, which ShellCheck does flag as it's undefined in
POSIX. So maybe it was actually triggered by the 'included' file?

I don't know if that could also be the case for the original reporter.

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Russ Allbery

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Jan 31, 2023, 4:40:04 PM1/31/23

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Diederik de Haas <didi....@cknow.org> writes:

> I looked a little deeper/further and specifically into
> `lib/coresight.sh` and that file does contain `echo -n`, which
> ShellCheck does flag as it's undefined in POSIX. So maybe it was
> actually triggered by the 'included' file?

> I don't know if that could also be the case for the original reporter.

Although echo -n is undefined in POSIX, Debian requires it to work in all
shells that are eligible to be /bin/sh. See:

https://www.debian.org/doc/debian-policy/ch-files.html#scripts

Diederik de Haas

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Jan 31, 2023, 4:50:04 PM1/31/23

to

On Tuesday, 31 January 2023 22:27:24 CET Russ Allbery wrote:
> Diederik de Haas <didi....@cknow.org> writes:
> > I looked a little deeper/further and specifically into
> > `lib/coresight.sh` and that file does contain `echo -n`, which
> > ShellCheck does flag as it's undefined in POSIX. So maybe it was
> > actually triggered by the 'included' file?
> >
> > I don't know if that could also be the case for the original reporter.
>
> Although echo -n is undefined in POSIX, Debian requires it to work in all
> shells that are eligible to be /bin/sh. See:
>
> https://www.debian.org/doc/debian-policy/ch-files.html#scripts

Ah, yeah, then lintian shouldn't trip over that.
I lack any Perl knowledge to (properly) understand the code snippet you posted
earlier or what lintian does in code, so I can't help with that.

Cheers,
Diederik

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