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<head>
<base href="https://bugs.llvm.org/">
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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 - Source line mapped to a nop at Og"
href="https://bugs.llvm.org/show_bug.cgi?id=51603">51603</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>Source line mapped to a nop at Og
</td>
</tr>
<tr>
<th>Product</th>
<td>libraries
</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>DebugInfo
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>artuso@diag.uniroma1.it
</td>
</tr>
<tr>
<th>CC</th>
<td>jdevlieghere@apple.com, keith.walker@arm.com, llvm-bugs@lists.llvm.org, paul_robinson@playstation.sony.com
</td>
</tr></table>
<p>
<div>
<pre>Comment:
Line 24 is associated to a single nop instruction. The expected behaviour
should be to point at line 0 when stepping on the nop.
Steps to reproduce bug:
root@ab3a2d7dacea:/home/stepping/output# clang -v
clang version 14.0.0 (<a href="https://github.com/llvm/llvm-project.git">https://github.com/llvm/llvm-project.git</a>
957334382cd12ec07b46c0ddfdcc220731f6d80f)
Target: x86_64-unknown-linux-gnu
Thread model: posix
InstalledDir: /usr/local/bin
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/7
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/7.5.0
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/8
Selected GCC installation: /usr/lib/gcc/x86_64-linux-gnu/7.5.0
Candidate multilib: .;@m64
Selected multilib: .;@m64
root@ab3a2d7dacea:/home/stepping/output# lldb -v
lldb version 14.0.0 (<a href="https://github.com/llvm/llvm-project.git">https://github.com/llvm/llvm-project.git</a> revision
957334382cd12ec07b46c0ddfdcc220731f6d80f)
clang revision 957334382cd12ec07b46c0ddfdcc220731f6d80f
llvm revision 957334382cd12ec07b46c0ddfdcc220731f6d80f
root@ab3a2d7dacea:/home/stepping/output# cat a.c
static int a ;
short g_1835 ;
char b ;
unsigned safe_add_func_uint8_t_u_u(char c, char d )
{
return c + d;
}
void e()
{
for (; ; ++a)
;
}
void func_1()
{
int f[] = {4,4,4};
char g ;
for (; b >= 0; b --)
{
if (3 != a)
;
else
if (g)
f[5] = 5;
for (g_1835 = 0; (g_1835 < 19); g_1835 =
safe_add_func_uint8_t_u_u(g_1835, 4))
{
g = 1;
for (; ; g ++)
if (f[g])
break;
}
}
}
int main ()
{
func_1();
}
root@ab3a2d7dacea:/home/stepping/output# cat -n a.c
1 static int a ;
2 short g_1835 ;
3 char b ;
4 unsigned safe_add_func_uint8_t_u_u(char c, char d )
5 {
6 return c + d;
7 }
8 void e()
9 {
10 for (; ; ++a)
11 ;
12 }
13 void func_1()
14 {
15 int f[] = {4,4,4};
16 char g ;
17 for (; b >= 0; b --)
18 {
19 if (3 != a)
20 ;
21 else
22 if (g)
23 f[5] = 5;
24 for (g_1835 = 0; (g_1835 < 19); g_1835 =
safe_add_func_uint8_t_u_u(g_1835, 4))
25 {
26 g = 1;
27 for (; ; g ++)
28 if (f[g])
29 break;
30 }
31 }
32 }
33 int main ()
34 {
35 func_1();
36 }
root@ab3a2d7dacea:/home/stepping/output# clang -g -Og a.c -o opt
a.c:23:33: warning: array index 5 is past the end of the array (which contains
3 elements) [-Warray-bounds]
f[5] = 5;
^ ~
a.c:15:5: note: array 'f' declared here
int f[] = {4,4,4};
^
1 warning generated.
root@ab3a2d7dacea:/home/stepping/output# lldb opt
(lldb) target create "opt"
Current executable set to '/home/stepping/output/opt' (x86_64).
(lldb) b main
Breakpoint 1: where = opt`main [inlined] func_1 at a.c:17:20, address =
0x00000000004004f0
(lldb) r
Process 45 launched: '/home/stepping/output/opt' (x86_64)
Process 45 stopped
* thread #1, name = 'opt', stop reason = breakpoint 1.1
frame #0: 0x00000000004004f0 opt`main [inlined] func_1 at a.c:17:20
14 {
15 int f[] = {4,4,4};
16 char g ;
-> 17 for (; b >= 0; b --)
18 {
19 if (3 != a)
20 ;
(lldb) si
Process 45 stopped
* thread #1, name = 'opt', stop reason = instruction step into
frame #0: 0x00000000004004f6 opt`main [inlined] func_1 at a.c:17:22
14 {
15 int f[] = {4,4,4};
16 char g ;
-> 17 for (; b >= 0; b --)
18 {
19 if (3 != a)
20 ;
(lldb) si
Process 45 stopped
* thread #1, name = 'opt', stop reason = instruction step into
frame #0: 0x00000000004004f8 opt`main [inlined] func_1 at a.c:17:13
14 {
15 int f[] = {4,4,4};
16 char g ;
-> 17 for (; b >= 0; b --)
18 {
19 if (3 != a)
20 ;
(lldb) si
Process 45 stopped
* thread #1, name = 'opt', stop reason = instruction step into
frame #0: 0x00000000004004fa opt`main [inlined] func_1 at a.c:17:13
14 {
15 int f[] = {4,4,4};
16 char g ;
-> 17 for (; b >= 0; b --)
18 {
19 if (3 != a)
20 ;
(lldb) si
Process 45 stopped
* thread #1, name = 'opt', stop reason = instruction step into
frame #0: 0x0000000000400500 opt`main [inlined] func_1 at a.c:0:13
1 static int a ;
2 short g_1835 ;
3 char b ;
4 unsigned safe_add_func_uint8_t_u_u(char c, char d )
5 {
6 return c + d;
7 }
(lldb) si
Process 45 stopped
* thread #1, name = 'opt', stop reason = instruction step into
frame #0: 0x0000000000400502 opt`main [inlined] func_1 at a.c:24:62
21 else
22 if (g)
23 f[5] = 5;
-> 24 for (g_1835 = 0; (g_1835 < 19); g_1835 =
safe_add_func_uint8_t_u_u(g_1835, 4))
25 {
26 g = 1;
27 for (; ; g ++)
(lldb) di -l
opt`main:
-> 0x400502 <+18>: nopw %cs:(%rax,%rax)
0x40050c <+28>: nopl (%rax)
4 unsigned safe_add_func_uint8_t_u_u(char c, char d )
5 {
** 6 return c + d;
7 }
8 void e()
0x400510 <+32>: movsbl %cl, %ecx
22 if (g)
23 f[5] = 5;
** 24 for (g_1835 = 0; (g_1835 < 19); g_1835 =
safe_add_func_uint8_t_u_u(g_1835, 4))
25 {
26 g = 1;
0x400513 <+35>: addl $0x4, %ecx
0x400516 <+38>: cmpw $0x13, %cx
0x40051a <+42>: jl 0x400510 ; <+32> [inlined]
safe_add_func_uint8_t_u_u + 14 at a.c:6:10
15 int f[] = {4,4,4};
16 char g ;
** 17 for (; b >= 0; b --)
18 {
19 if (3 != a)
0x40051c <+44>: leal -0x1(%rax), %ecx
0x40051f <+47>: testb %al, %al
(lldb) si
Process 45 stopped
* thread #1, name = 'opt', stop reason = instruction step into
frame #0: 0x000000000040050c opt`main [inlined]
safe_add_func_uint8_t_u_u(c='\0', d='\x04') at a.c:0:13
1 static int a ;
2 short g_1835 ;
3 char b ;
4 unsigned safe_add_func_uint8_t_u_u(char c, char d )
5 {
6 return c + d;
7 }
(lldb) di -l
opt`main:
0x400500 <+16>: xorl %ecx, %ecx
0x400502 <+18>: nopw %cs:(%rax,%rax)
-> 0x40050c <+28>: nopl (%rax)</pre>
</div>
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