[4288] in BarnOwl Developers
[barnowl/barnowl] owl.c: declare getopt_long return variable as int
daemon@ATHENA.MIT.EDU (Daniel JB Clark)
Sun Nov 1 12:31:01 2026
Date: Sun, 01 Nov 2026 09:30:55 -0800
From: Daniel JB Clark <notifications@github.com>
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### Summary
In `owl_parse_options` (`owl.c`), `c` was declared as `char c;` to hold the return value of `getopt_long(...)`.
On architectures where `char` is unsigned by default (such as ARM/aarch64, PowerPC, and s390x), `(c = getopt_long(...)) != -1` is never false because `getopt_long`'s `-1` return value is converted to `(unsigned char)-1` (`255`), which does not equal `-1`. This causes BarnOwl on arm64 systems to immediately enter the `default:` branch of the option switch, print usage, and exit 1 upon launch.
Declaring `int c;` correctly matches `getopt_long`'s return type and preserves the `-1` sentinel across all architectures without requiring `-fsigned-char`.
### Verification
- Tested with standard POSIX `getopt_long` parsing behavior on aarch64 Linux.
- Prior duplicate search conducted on `barnowl/barnowl` PRs and issues for `getopt`, `arm64`, `signed char`, and `unsigned char` (no existing open or closed matches found).
- Adversary review: no findings (type widening to standard `int` matches `getopt_long` prototype).
You can view, comment on, or merge this pull request online at:
https://github.com/barnowl/barnowl/pull/191
-- Commit Summary --
* owl.c: declare getopt_long return variable as int for unsigned char architectures
-- File Changes --
M owl.c (2)
-- Patch Links --
https://github.com/barnowl/barnowl/pull/191.patch
https://github.com/barnowl/barnowl/pull/191.diff
--
Reply to this email directly or view it on GitHub:
https://github.com/barnowl/barnowl/pull/191
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<h3 dir=3D"auto">Summary</h3>
<p dir=3D"auto">In <code class=3D"notranslate">owl_parse_options</code> (=
<code class=3D"notranslate">owl.c</code>), <code class=3D"notranslate">c<=
/code> was declared as <code class=3D"notranslate">char c;</code> to hold=
the return value of <code class=3D"notranslate">getopt_long(...)</code>.=
</p>
<p dir=3D"auto">On architectures where <code class=3D"notranslate">char</=
code> is unsigned by default (such as ARM/aarch64, PowerPC, and s390x), <=
code class=3D"notranslate">(c =3D getopt_long(...)) !=3D -1</code> is nev=
er false because <code class=3D"notranslate">getopt_long</code>'s <code c=
lass=3D"notranslate">-1</code> return value is converted to <code class=3D=
"notranslate">(unsigned char)-1</code> (<code class=3D"notranslate">255</=
code>), which does not equal <code class=3D"notranslate">-1</code>. This =
causes BarnOwl on arm64 systems to immediately enter the <code class=3D"n=
otranslate">default:</code> branch of the option switch, print usage, and=
exit 1 upon launch.</p>
<p dir=3D"auto">Declaring <code class=3D"notranslate">int c;</code> corre=
ctly matches <code class=3D"notranslate">getopt_long</code>'s return type=
and preserves the <code class=3D"notranslate">-1</code> sentinel across =
all architectures without requiring <code class=3D"notranslate">-fsigned-=
char</code>.</p>
<h3 dir=3D"auto">Verification</h3>
<ul dir=3D"auto">
<li>Tested with standard POSIX <code class=3D"notranslate">getopt_long</c=
ode> parsing behavior on aarch64 Linux.</li>
<li>Prior duplicate search conducted on <code class=3D"notranslate">barno=
wl/barnowl</code> PRs and issues for <code class=3D"notranslate">getopt</=
code>, <code class=3D"notranslate">arm64</code>, <code class=3D"notransla=
te">signed char</code>, and <code class=3D"notranslate">unsigned char</co=
de> (no existing open or closed matches found).</li>
<li>Adversary review: no findings (type widening to standard <code class=3D=
"notranslate">int</code> matches <code class=3D"notranslate">getopt_long<=
/code> prototype).</li>
</ul>
<hr>
<h4>You can view, comment on, or merge this pull request online at:</h4>
<p> <a href=3D'https://github.com/barnowl/barnowl/pull/191'>ht=
tps://github.com/barnowl/barnowl/pull/191</a></p>
<h4>Commit Summary</h4>
<ul>
<li><a href=3D"https://github.com/barnowl/barnowl/pull/191/commits/ae58=
d34d0451c261bfde962ca66875b049ed008f" class=3D"commit-link">ae58d34</a> =
owl.c: declare getopt_long return variable as int for unsigned char archi=
tectures</li>
</ul>
<h4 style=3D"display: inline-block">File Changes </h4> <p style=3D"displa=
y: inline-block">(<a href=3D"https://github.com/barnowl/barnowl/pull/191/=
files">1 file</a>)</p>
<ul>
<li>
<strong>M</strong>
<a href=3D"https://github.com/barnowl/barnowl/pull/191/files#diff-7aa=
159174e27b0be5736ce16ff757bade110f533505958a6e3b55a4edb732697">owl.c</a>
(2)
</li>
</ul>
<h4>Patch Links:</h4>
<ul>
<li><a href=3D'https://github.com/barnowl/barnowl/pull/191.patch'>https=
://github.com/barnowl/barnowl/pull/191.patch</a></li>
<li><a href=3D'https://github.com/barnowl/barnowl/pull/191.diff'>https:=
//github.com/barnowl/barnowl/pull/191.diff</a></li>
</ul>
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