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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - Problem with tenary operator and errno: although condition is true it evaluates the else part"
href="http://llvm.org/bugs/show_bug.cgi?id=18644">18644</a>
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<th>Summary</th>
<td>Problem with tenary operator and errno: although condition is true it evaluates the else part
</td>
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<th>Product</th>
<td>clang
</td>
</tr>
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<th>Version</th>
<td>3.4
</td>
</tr>
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<th>Hardware</th>
<td>PC
</td>
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<th>OS</th>
<td>Linux
</td>
</tr>
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<th>Status</th>
<td>NEW
</td>
</tr>
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<th>Severity</th>
<td>normal
</td>
</tr>
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<th>Priority</th>
<td>P
</td>
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<th>Component</th>
<td>-New Bugs
</td>
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<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
</td>
</tr>
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<th>Reporter</th>
<td>christian@2ndquadrant.com
</td>
</tr>
<tr>
<th>CC</th>
<td>llvmbugs@cs.uiuc.edu
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<th>Classification</th>
<td>Unclassified
</td>
</tr></table>
<p>
<div>
<pre>Hi,
while working on a patch for PostgreSQL I noticed that a error hint was not
displayed. The hint has been set via a ternary operator and a comparison of
errno:
ereport(FATAL,
(errmsg("could not map anonymous shared memory: %m"),
(errno == ENOMEM) ?
errhint("This error usually means that PostgreSQL's
request "
"for a shared memory segment exceeded available
memory "
"or swap space. To reduce the request size
(currently "
"%zu bytes), reduce PostgreSQL's shared memory
usage, "
"perhaps by reducing shared_buffers or "
"max_connections.",
*size) : 0));
In this case (checked with GDB) is errno == ENOMEM, but the hint wont appear.
The same code works fine with GCC.
clang version used:
clang version 3.4 (tags/RELEASE_34/final)
Target: x86_64-pc-linux-gnu
Thread model: posix
gcc version used:
gcc (Gentoo 4.7.3-r1 p1.4, pie-0.5.5) 4.7.3
Copyright (C) 2012 Free Software Foundation, Inc.
This is free software; see the source for copying conditions. There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
I wasn't able to create a small test case, but I uploaded my current working
tree so you can check it out:
<a href="http://www.defunced.de/postgres-working-tree.tgz">http://www.defunced.de/postgres-working-tree.tgz</a>
The compiler flags I used are in both cases (gcc and clang):
-O0 -g -W -Wall -ansi -pedantic -pipe -std=c99 -Wall -Wmissing-prototypes
-Wpointer-arith -Wdeclaration-after-statement -Wendif-labels
-Wmissing-format-attribute -Wformat-security -fno-strict-aliasing -fwrapv
-fexcess-precision=standard
I configured with this statement for clang:
CFLAGS="-O0 -g -W -Wall -ansi -pedantic -pipe -std=c99" CC=/usr/bin/clang
./configure --prefix=/home/ckruse/dev/postgres/
and with this for GCC:
CFLAGS="-O0 -g -W -Wall -ansi -pedantic -pipe -std=c99" ./configure
--prefix=/home/ckruse/dev/postgres/
Best regards,
--
Christian Kruse <a href="http://www.2ndQuadrant.com/">http://www.2ndQuadrant.com/</a>
PostgreSQL Development, 24x7 Support, Training & Services</pre>
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