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<base href="http://llvm.org/bugs/" />
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<body><table border="1" cellspacing="0" cellpadding="8">
<tr>
<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - possible wrongful crash from undefined sanitizer"
href="http://llvm.org/bugs/show_bug.cgi?id=17635">17635</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>possible wrongful crash from undefined sanitizer
</td>
</tr>
<tr>
<th>Product</th>
<td>new-bugs
</td>
</tr>
<tr>
<th>Version</th>
<td>trunk
</td>
</tr>
<tr>
<th>Hardware</th>
<td>PC
</td>
</tr>
<tr>
<th>OS</th>
<td>Linux
</td>
</tr>
<tr>
<th>Status</th>
<td>NEW
</td>
</tr>
<tr>
<th>Severity</th>
<td>normal
</td>
</tr>
<tr>
<th>Priority</th>
<td>P
</td>
</tr>
<tr>
<th>Component</th>
<td>new bugs
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>regehr@cs.utah.edu
</td>
</tr>
<tr>
<th>CC</th>
<td>llvmbugs@cs.uiuc.edu
</td>
</tr>
<tr>
<th>Classification</th>
<td>Unclassified
</td>
</tr></table>
<p>
<div>
<pre>I can't see anything wrong with the code below yet it throws an illegal
instruction. Note that the packed and unpacked structs have the same field
offsets in 32-bit mode.
$ clang -m32 -O -fsanitize=undefined main.c ; ./a.out
24 23
Illegal instruction
$ cat main.c
#include <stdio.h>
#include <assert.h>
struct s2 {
long long f0;
long f1;
unsigned int f2;
unsigned long f3;
short f4;
unsigned char f5;
};
#pragma pack (1)
struct s2_packed {
long long f0;
long f1;
unsigned int f2;
unsigned long f3;
short f4;
unsigned char f5;
};
#pragma pack ()
void copy (char* out, char* in)
{
int i;
for (i = 0; i < 23; i++) out[i] = in[i];
}
int main (void)
{
struct s2 topack1 = {48098, 3948348, 234985, 32034849, 3432, 'u'};
struct s2_packed packed1;
printf ("%d %d\n", sizeof (struct s2), sizeof (struct s2_packed));
copy((char*)&packed1, (char*)&topack1);
assert(topack1.f0 == packed1.f0);
assert(topack1.f1 == packed1.f1);
assert(topack1.f2 == packed1.f2);
assert(topack1.f3 == packed1.f3);
assert(topack1.f4 == packed1.f4);
assert(topack1.f5 == packed1.f5);
printf("Tests Complete.\n");
return 0;
}
$ clang -v
clang version 3.4 (trunk 193086)
Target: x86_64-unknown-linux-gnu
Thread model: posix
Found candidate GCC installation: /usr/lib/gcc/i686-linux-gnu/4.7
Found candidate GCC installation: /usr/lib/gcc/i686-linux-gnu/4.7.3
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.4
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.4.7
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.6
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.6.4
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.7
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.7.3
Selected GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.7</pre>
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