GNU bug report logs - #20947
libtool 2.4.2 is not robust to a missing global_symbol_pipe

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Subject: libtool 2.4.2 is not robust to a missing global_symbol_pipe
From: Philip Chimento <philip.chimento@HIDDEN>
To: bug-libtool@HIDDEN
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This is a difficult-to-reproduce bug since it only occurs due to outside
influences. However, I believe libtool's behaviour could be improved to
make it more obvious what is going on when the bug occurs.

Many instances of the symptom can be found by doing an internet search for
"libtool global_symbol_pipe". Basically the configure check for the sed
expression to parse the output of nm can fail, without causing configure to
abort.

    checking command to parse /usr/bin/nm -B output from gcc object...
failed

This results in the variable global_symbol_pipe being empty in the
generated libtool script, which causes compilation to fail later on:

    libtool: link: /usr/bin/nm -B <OBJECT-FILES> | | /bin/sed 's/.* //' |
sort | uniq > <EXPORTED-SYMBOL-FILE>

    ./libtool: eval: line <LINE>: syntax error near unexpected token `|'

(The empty space between the pipes is where the empty global_symbol_pipe
variable is plugged in.)

That this happens is not libtool's fault, it's generally caused by a
misconfigured nm. However, I believe it would lead to fewer headaches for
libtool users if configure aborted with an explanation, or the libtool
script itself was more robust to the empty variable and didn't try to pipe
nm output through nothing.

Regards,
-- 
Philip

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<div dir=3D"ltr">This is a difficult-to-reproduce bug since it only occurs =
due to outside influences. However, I believe libtool&#39;s behaviour could=
 be improved to make it more obvious what is going on when the bug occurs.<=
div><br></div><div>Many instances of the symptom can be found by doing an i=
nternet search for &quot;libtool global_symbol_pipe&quot;. Basically the co=
nfigure check for the sed expression to parse the output of nm can fail, wi=
thout causing configure to abort.</div><div><br></div><div>=C2=A0 =C2=A0=C2=
=A0checking command to parse /usr/bin/nm -B output from gcc object... faile=
d</div><div><br></div><div>This results in the variable global_symbol_pipe =
being empty in the generated libtool script, which causes compilation to fa=
il later on:</div><br>=C2=A0 =C2=A0 libtool: link: /usr/bin/nm -B &lt;OBJEC=
T-FILES&gt; | | /bin/sed &#39;s/.* //&#39; | sort | uniq &gt; &lt;EXPORTED-=
SYMBOL-FILE&gt;<br><br>=C2=A0 =C2=A0 ./libtool: eval: line &lt;LINE&gt;: sy=
ntax error near unexpected token `|&#39;<div><br></div><div>(The empty spac=
e between the pipes is where the empty global_symbol_pipe variable is plugg=
ed in.)</div><div><br></div><div>That this happens is not libtool&#39;s fau=
lt, it&#39;s generally caused by a misconfigured nm. However, I believe it =
would lead to fewer headaches for libtool users if configure aborted with a=
n explanation, or the libtool script itself was more robust to the empty va=
riable and didn&#39;t try to pipe nm output through nothing.<br><div><br><d=
iv>Regards,</div>-- <br><div class=3D"gmail_signature">Philip</div>
</div></div></div>

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