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<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 - inconsistent behaviors for calling function va_arg() at -O3 (-O0 is correct)"
href="https://bugs.llvm.org/show_bug.cgi?id=46014">46014</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>inconsistent behaviors for calling function va_arg() at -O3 (-O0 is correct)
</td>
</tr>
<tr>
<th>Product</th>
<td>lldb
</td>
</tr>
<tr>
<th>Version</th>
<td>unspecified
</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>All Bugs
</td>
</tr>
<tr>
<th>Assignee</th>
<td>lldb-dev@lists.llvm.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>yangyibiao@hust.edu.cn
</td>
</tr>
<tr>
<th>CC</th>
<td>jdevlieghere@apple.com, llvm-bugs@lists.llvm.org
</td>
</tr></table>
<p>
<div>
<pre>$ clang --version
clang version 11.0.0 (/home/yibiao/.cache/yay/llvm-git/llvm-project
871beba234a83a2a02da9dedbd59b91a1bfbd7af)
Target: x86_64-pc-linux-gnu
Thread model: posix
InstalledDir: /usr/bin
$ lldb --version
lldb version 11.0.0
clang revision 871beba234a83a2a02da9dedbd59b91a1bfbd7af
llvm revision 871beba234a83a2a02da9dedbd59b91a1bfbd7af
$ cat small.c
#include <stdarg.h>
void f(int i, ...) {
int j;
double d;
char *s;
va_list ap;
va_start(ap, i);
j = va_arg(ap, int);
d = va_arg(ap, double);
s = va_arg(ap, char *);
va_end(ap);
}
int main() {
f(1);
return 0;
}
$ clang -g -O3 small.c; lldb a.out
(lldb) target create "a.out"
Current executable set to '/home/yibiao/Debugger/a.out' (x86_64).
(lldb) b main
Breakpoint 1: where = a.out`main + 1 at small.c:16:3, address =
0x00000000004011e1
(lldb) r
Process 139129 launched: '/home/yibiao/Debugger/a.out' (x86_64)
Process 139129 stopped
* thread #1, name = 'a.out', stop reason = breakpoint 1.1
frame #0: 0x00000000004011e1 a.out`main at small.c:16:3
13 }
14
15 int main() {
-> 16 f(1);
17 return 0;
18 }
(lldb) si -c 26
Process 139129 stopped
* thread #1, name = 'a.out', stop reason = instruction step into
frame #0: 0x00000000004011c7 a.out`f(i=<unavailable>) at small.c:11:7
8 va_start(ap, i);
9 j = va_arg(ap, int);
10 d = va_arg(ap, double);
-> 11 s = va_arg(ap, char *);
12 va_end(ap);
13 }
14
(lldb)
/******************************
As showed above, Line 11 is hit by lldb when using "instruction level" step.
However, Line 11 is not hit by lldb when setting breakpoint on it as follow:
******************************/
$ clang -g -O3 small.c; lldb a.out
(lldb) target create "a.out"
Current executable set to '/home/yibiao/Debugger/a.out' (x86_64).
(lldb) b 11
Breakpoint 1: where = a.out`f + 142 at small.c:11:7, address =
0x000000000040119e
(lldb) r
Process 138683 launched: '/home/yibiao/Debugger/a.out' (x86_64)
Process 138683 exited with status = 0 (0x00000000)
(lldb)</pre>
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