It's ok, solved it!
struct Test
{
uintptr_t msg;
};
:-D
Jono
-------- Original Message --------
Subject: reading std::string contents with dtrace?
Date: Wed, 25 Jun 2014 14:11:06 +1200
From: Jono Poff <jonathan.p...@taitradio.com>
To: dtrace-discuss@lists.dtrace.org
Hi,
I have 2 test setups (see below....). test0 reads the contents of a
struct and test1 reads the contents of a std::string.
these both work as expected, ie.....
====== test0
# dtrace -s test0.d -p `pgrep test0` -32 -q
dtrace: script 'test0.d' matched 2 probes
Z ...zzzz
Q ...qqqq
====== test1
# dtrace -s test1.d -p `pgrep test1` -32 -q
dtrace: script 'test1.d' matched 2 probes
XXXX
RRRR
======
However, what I actually require is a probe that can read a struct with
a std::string member, eg:
struct Test
{
std::string msg;
};
How can I declare this struct in the dtrace script and also how does
dtrace actually interpret the std::string layout. Is it magic or logic?
If it's possible, could I please have a worked example? :o)
Cheers,
Jono
====================================================================
test.cpp
#include<string>
#include <unistd.h>
using std::string;
enum{SZ=100};
struct Test
{
char c;
char msg[SZ];
};
Test *xxx(Test *t)
{
strncpy(t->msg, "qqqq", SZ-1);
t->c='Q';
return t;
}
int main()
{
Test test;
while(true)
{
strncpy(test.msg, "zzzz", SZ-1);
test.c='Z';
xxx(&test);
sleep(1);
}
}
==================================================================== test.d
enum{SZ=100};
struct Test
{
char c;
char msg[SZ];
};
pid$target::_Z3xxxP4Test:entry
{
this->test = (struct Test *) copyin ( arg0, sizeof ( struct
Test ) );
printf("\n%c ...%s ", this->test->c, this->test->msg);
}
pid$target::_Z3xxxP4Test:entry
{
this->test = (struct Test *) copyin ( arg0, sizeof ( struct
Test ) );
printf("\n%c ...%s ", this->test->c, this->test->msg);
}
pid$target::_Z3xxxP4Test:return
{
this->test = (struct Test *) copyin ( arg1, sizeof ( struct
Test ) );
printf("\n%c ...%s", this->test->c, this->test->msg);
}
====================================================================
====================================================================
====================================================================
====================================================================
test1.cpp
#include<string>
#include <unistd.h>
using std::string;
string xxx(string &t)
{
t = "RRRR";
return t;
}
int main()
{
string test;
while(true)
{
test = "XXXX";
xxx(test);
sleep(1);
}
}
====================================================================
test1.cpp
pid$target::_Z3xxxRSs:entry
{
this->str = *((uintptr_t*)copyin(arg0, sizeof(void*)));
printf("\n%s", copyinstr(this->str));
}
pid$target::_Z3xxxRSs:return
{
this->str = *((uintptr_t*)copyin(arg1, sizeof(void*)));
printf("\n%s", copyinstr(this->str));
}
====================================================================
====================================================================
====================================================================
====================================================================
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