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<base href="http://llvm.org/bugs/" />
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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - Address sanitizer interacts badly with -Wl,--as-needed on linux"
href="http://llvm.org/bugs/show_bug.cgi?id=15823">15823</a>
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<th>Summary</th>
<td>Address sanitizer interacts badly with -Wl,--as-needed on linux
</td>
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<th>Product</th>
<td>clang
</td>
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<th>Version</th>
<td>unspecified
</td>
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<th>Hardware</th>
<td>PC
</td>
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<th>OS</th>
<td>All
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<th>Status</th>
<td>NEW
</td>
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<th>Severity</th>
<td>normal
</td>
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<th>Priority</th>
<td>P
</td>
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<th>Component</th>
<td>Driver
</td>
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<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
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<th>Reporter</th>
<td>nicolasweber@gmx.de
</td>
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<th>CC</th>
<td>llvmbugs@cs.uiuc.edu
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<th>Classification</th>
<td>Unclassified
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<p>
<div>
<pre>On Ubuntu Lucid:
thakis@yearofthelinuxdesktop:/usr/local/google/chrome/src$ cat test.cc
#include <dlfcn.h>
#include <stdio.h>
#include <time.h>
int main() {
struct timespec ts; clock_gettime(CLOCK_REALTIME, &ts);
printf("%p\n", dlsym(RTLD_NEXT, "malloc"));
printf("%p\n", dlsym(RTLD_NEXT, "clock_gettime"));
}
thakis@yearofthelinuxdesktop:/usr/local/google/chrome/src$
third_party/llvm-build/Release+Asserts/bin/clang -fsanitize=address
-Wl,--as-needed -o foo test.cc -ldl -lrt
thakis@yearofthelinuxdesktop:/usr/local/google/chrome/src$ ./foo
ASAN:SIGSEGV
=================================================================
==2748==ERROR: AddressSanitizer: SEGV on unknown address 0x000000000000 (pc
0x000000000000 sp 0x7fff99327e98 bp 0x7fff99327ed0 T0)
AddressSanitizer can not provide additional info.
==2748==ABORTING
This happens because ld ends up not linking in librt:
thakis@yearofthelinuxdesktop:/usr/local/google/chrome/src$ ldd foo
linux-vdso.so.1 => (0x00007fffc41ba000)
libdl.so.2 => /lib/libdl.so.2 (0x00007ffa37f07000)
libpthread.so.0 => /lib/libpthread.so.0 (0x00007ffa37cea000)
libgcc_s.so.1 => /lib/libgcc_s.so.1 (0x00007ffa37ad2000)
libc.so.6 => /lib/libc.so.6 (0x00007ffa3774c0
However, asan (and the other sans, I think) rely on dlsym(RTLD_NEXT,
"clock_gettime") to return a valid function so that the intercepting function
can call through to the real function. But since there's no dependency on
librt.1.so, dlsym() just returns NULL.
The only thing I can think of that can be done about this is to have the driver
strip out --as-needed when doing a sanitizer build.</pre>
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