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<base href="https://llvm.org/bugs/" />
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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 --- - __dfsw_memchr is miscompiled by llvm" href="https://urldefense.proofpoint.com/v2/url?u=https-3A__llvm.org_bugs_show-5Fbug.cgi-3Fid-3D23964&d=AwMBaQ&c=8hUWFZcy2Z-Za5rBPlktOQ&r=pF93YEPyB-J_PERP4DUZOJDzFVX5ZQ57vQk33wu0vio&m=JAWyx5l0PaIeIhDV8DX_Mut8cMT01-ucDdGp8jvcvyo&s=jRj7U6PAtqTaR7HBAIgpuz1kX9PGp7sRhzgKZ_ECpZc&e=">23964</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>__dfsw_memchr is miscompiled by llvm
</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>hjl.tools@gmail.com
</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>On Fedora/21 x86-64, llvm r240771 miscompiled __dfsw_memchr:
Command Output (stderr):
--
/export/gnu/import/git/llvm/projects/compiler-rt/test/dfsan/custom.cc:817:39:
warning: data argument not used by format string [-Wformat-extra-args]
assert(sprintf(buf, "Hello world!", 42, "hello") == 12);
~~~~~~~~~~~~~~ ^
/usr/include/assert.h:86:5: note: expanded from macro 'assert'
((expr) \
^
1 warning generated.
custom.cc.tmp:
/export/gnu/import/git/llvm/projects/compiler-rt/test/dfsan/custom.cc:698: void
test_memchr(): Assertion `crv == &str1[2]' failed.
/export/build/gnu/llvm-clang-bootstrap-cmake/stage2/build-x86_64-linux/projects/compiler-rt/test/dfsan/Output/custom.cc.script:
line 4: 14618 Aborted
DFSAN_OPTIONS="strict_data_dependencies=0"
/export/build/gnu/llvm-clang-bootstrap-cmake/stage2/build-x86_64-linux/projects/compiler-rt/test/dfsan/Output/custom.cc.tmp
Dump of assembler code for function __dfsw_memchr:
0x0000555555559630 <+0>: push %rbp
0x0000555555559631 <+1>: push %r15
0x0000555555559633 <+3>: push %r14
0x0000555555559635 <+5>: push %rbx
0x0000555555559636 <+6>: push %rax
0x0000555555559637 <+7>: mov %r8d,%ebx
0x000055555555963a <+10>: mov %ecx,%ebp
0x000055555555963c <+12>: mov 0x30(%rsp),%r15
=> 0x0000555555559641 <+17>: lea 0x3b91d0(%rip),%rax #
0x555555912818 <_ZN7__dfsan10flags_dataE>
0x0000555555559648 <+24>: cmpb $0x0,0x2(%rax)
0x000055555555964c <+28>: je 0x555555559652 <__dfsw_memchr+34>
0x000055555555964e <+30>: xor %eax,%eax
0x0000555555559650 <+32>: jmp 0x555555559675 <__dfsw_memchr+69>
0x0000555555559652 <+34>: mov %rdx,%rsi
0x0000555555559655 <+37>: callq 0x555555557e60 <dfsan_read_label()>
0x000055555555965a <+42>: mov %ax,%r14w
0x000055555555965e <+46>: movzwl %bp,%edi
0x0000555555559661 <+49>: movzwl %bx,%esi
0x0000555555559664 <+52>: callq 0x555555557c50 <dfsan_union>
0x0000555555559669 <+57>: movzwl %r14w,%edi
0x000055555555966d <+61>: movzwl %ax,%esi
__dfsw_memchr compiled with g++:
Dump of assembler code for function __dfsw_memchr(void*, int, size_t,
dfsan_label, dfsan_label, dfsan_label, dfsan_label*):
0x0000000000006b30 <+0>: push %r14
0x0000000000006b32 <+2>: push %r13
0x0000000000006b34 <+4>: mov %r8d,%r14d
0x0000000000006b37 <+7>: push %r12
0x0000000000006b39 <+9>: push %rbp
0x0000000000006b3a <+10>: mov %rdi,%r13
0x0000000000006b3d <+13>: push %rbx
0x0000000000006b3e <+14>: mov %ecx,%r12d
0x0000000000006b41 <+17>: mov %rdx,%rbx
0x0000000000006b44 <+20>: callq 0x37e0 <memchr@plt>
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
It is missing from llvm.
0x0000000000006b49 <+25>: mov %rax,%rbp
0x0000000000006b4c <+28>: lea 0x23e8fd(%rip),%rax # 0x245450
<_ZN7__dfsan10flags_dataE>
0x0000000000006b53 <+35>: cmpb $0x0,0x2(%rax)
0x0000000000006b57 <+39>: je 0x6b80 <__dfsw_memchr(void*, int,
size_t, dfsan_label, dfsan_label, dfsan_label, dfsan_label*)+80>
0x0000000000006b59 <+41>: mov 0x30(%rsp),%rax
0x0000000000006b5e <+46>: test %rbp,%rbp
0x0000000000006b61 <+49>: mov $0x0,%ecx
0x0000000000006b66 <+54>: cmove %ecx,%r12d
0x0000000000006b6a <+58>: mov %r12w,(%rax)
It happens on Fedora/21, not on Fedora 20. It worked on Fedora 21
on May 30, 2015.</pre>
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