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<base href="https://bugs.llvm.org/">
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<body><table border="1" cellspacing="0" cellpadding="8">
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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - Clang produces incorrect code at -O0"
href="https://bugs.llvm.org/show_bug.cgi?id=34381">34381</a>
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</tr>
<tr>
<th>Summary</th>
<td>Clang produces incorrect code at -O0
</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>enhancement
</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>Vsevolod.Livinskij@frtk.ru
</td>
</tr>
<tr>
<th>CC</th>
<td>llvm-bugs@lists.llvm.org
</td>
</tr></table>
<p>
<div>
<pre>Clang produces wrong-code with -O0.
<span class="quote">>$ cat driver.cpp </span >
#include <stdio.h>
extern const signed char var_11;
extern const unsigned int var_21;
extern const signed char var_29;
extern signed char var_370;
extern unsigned int var_390;
const signed char var_11 = 97;
const unsigned int var_21 = 3536697529U;
const signed char var_29 = 20;
signed char var_370 = 16;
unsigned int var_390 = 1082014357U;
extern void foo ();
int main () {
foo ();
printf("%llu\n", var_390);
return 0;
}
<span class="quote">>$ cat func.cpp </span >
extern const signed char var_11;
extern const unsigned int var_21;
extern const signed char var_29;
extern signed char var_370;
extern unsigned int var_390;
void foo() {
var_390 = !char((var_21 < -var_29) + ~0);
var_370 = short(var_11);
}
<span class="quote">>$ clang++ -O1 driver.cpp func.cpp ; ./a.out </span >
1
<span class="quote">>$ clang++ -O0 driver.cpp func.cpp ; ./a.out </span >
0
clang version 6.0.0 (trunk 311997)</pre>
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