From: "agentzh at gmail dot com" <sourceware-bugzilla@sourceware.org>
To: systemtap@sourceware.org
Subject: [Bug tapsets/23799] New: sprint_ustack() returns empty strings while sprint_ubacktrace() does not
Date: Fri, 19 Oct 2018 18:59:00 -0000 [thread overview]
Message-ID: <bug-23799-6586@http.sourceware.org/bugzilla/> (raw)
https://sourceware.org/bugzilla/show_bug.cgi?id=23799
Bug ID: 23799
Summary: sprint_ustack() returns empty strings while
sprint_ubacktrace() does not
Product: systemtap
Version: unspecified
Status: UNCONFIRMED
Severity: normal
Priority: P2
Component: tapsets
Assignee: systemtap at sourceware dot org
Reporter: agentzh at gmail dot com
Target Milestone: ---
Consider the following minimal C program:
```
int foo(void) {
return 3;
}
int bar(void) {
return foo();
}
int main(void) {
bar();
return 0;
}
```
Compile and link it like this:
```
gcc -g test.c
```
And then run the following stap oneliner:
```
stap -e 'probe process.function("foo") { printf("{%s}\n{%s}",
sprint_ustack(ubacktrace()), sprint_ubacktrace()); }' -c ./a.out --ldd
```
And the output is
```
{}
{foo+0x4 [a.out]
bar+0x9 [a.out]
main+0x9 [a.out]
__libc_start_main+0xea [libc-2.26.so]
_start+0x2a [a.out]}
```
The weird thing is that `sprint_ustack(ubacktrace())` returns an empty string
while `sprint_ubacktrace()` does not. Why the difference? Is there a bug in
`sprint_ustack()`? Any hints on debugging this thing?
Thanks!
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next reply other threads:[~2018-10-19 18:59 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-10-19 18:59 agentzh at gmail dot com [this message]
2018-10-19 19:01 ` [Bug tapsets/23799] " agentzh at gmail dot com
2018-10-19 21:15 ` agentzh at gmail dot com
2018-10-19 22:12 ` agentzh at gmail dot com
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