[Interest] Creating a debug log with a stacktrace on Linux
Rogers Nate
nate.rogers at raymondcorp.com
Thu Jun 26 16:05:35 CEST 2014
I am trying to capture some debug information to eventually add to a log in my application but my stacktrace doesn't contain the actual names of the functions that are being call (at least that I can see). How can I get a stack trace that is more meaningful or easier to read?
main.cpp
-------------------------------------------------------------------------------------------------------
#include "FiveWayDriver.h"
const char* get_process_name_by_pid(const int pid)
{
char* name = (char*)calloc(1024,sizeof(char));
if(name){
sprintf(name, "/proc/%d/cmdline",pid);
FILE* f = fopen(name,"r");
if(f){
size_t size;
size = fread(name, sizeof(char), 1024, f);
if(size>0){
if('\n'==name[size-1])
name[size-1]='\0';
}
fclose(f);
}
}
return name;
}
/** Print a demangled stack backtrace of the caller function to FILE* out. */
static inline void print_stacktrace()
{
unsigned int max_frames = 63;
qDebug() << "stack trace:";
// storage array for stack trace address data
void* addrlist[max_frames+1];
// retrieve current stack addresses
int addrlen = backtrace(addrlist, sizeof(addrlist) / sizeof(void*));
if (addrlen == 0)
{
qDebug() << " <empty, possibly corrupt>";
return;
}
// resolve addresses into strings containing "filename(function+address)", this array must be free()-ed
char** symbollist = backtrace_symbols(addrlist, addrlen);
// allocate string which will be filled with the demangled function name
size_t funcnamesize = 256;
char* funcname = (char*)malloc(funcnamesize);
// iterate over the returned symbol lines. skip the first, it is the address of this function.
for (int i = 1; i < addrlen; i++)
{
char *begin_name = 0, *begin_offset = 0, *end_offset = 0;
for (char *p = symbollist[i]; *p; ++p)
{
if (*p == '(')
begin_name = p;
else if (*p == '+')
begin_offset = p;
else if (*p == ')' && begin_offset) {
end_offset = p;
break;
}
}
if (begin_name && begin_offset && end_offset
&& begin_name < begin_offset)
{
*begin_name++ = '\0';
*begin_offset++ = '\0';
*end_offset = '\0';
int status;
char* ret = abi::__cxa_demangle(begin_name,
funcname, &funcnamesize, &status);
if (status == 0)
{
funcname = ret; // use possibly realloc()-ed string
qDebug() << " " << symbollist[i] << " : " << funcname << "+" << begin_offset;
}
else
{
// demangling failed. Output function name as a C function with
// no arguments.
qDebug() << " " << symbollist[i] << " : " << begin_name << "+" << begin_offset;
}
}
else
{
// couldn't parse the line? print the whole line.
qDebug() << " " << symbollist[i];
}
}
free(funcname);
free(symbollist);
}
void sighandler(int signum)
{
qDebug() << "Process" << get_process_name_by_pid(getpid()) << " got signal " << signum;
print_stacktrace();
signal(signum, SIG_DFL);
kill(getpid(), signum);
}
int main(int argc, char *argv[])
{
QCoreApplication app(argc, argv);
// Create the five-way driver
FiveWayDriver fiveWayDriver;
// install our handler
signal(SIGSEGV, sighandler);
signal(SIGTERM, sighandler);
return app.exec();
}
-------------------------------------------------------------------------------------------------------
FiveWayDriver.cpp
-------------------------------------------------------------------------------------------------------
#include "FiveWayDriver.h"
FiveWayDriver::FiveWayDriver()
{
// Setup the timer
m_Timer = new QTimer(this);
connect(m_Timer, SIGNAL(timeout()), this, SLOT(processFiveWayButton()));
m_Timer->start(1000);
}
void FiveWayDriver::upButtonClicked()
{
int *foo = (int*)-1; // make a bad pointer
printf("%d\n", *foo); // causes segfault
}
void FiveWayDriver::processFiveWayButton()
{
upButtonClicked();
}
void FiveWayDriver::toggleTimer()
{
if (m_Timer->isActive())
{
m_Timer->stop();
}
else
{
m_Timer->start();
}
}
-------------------------------------------------------------------------------------------------------
FiveWayDriver.h
-------------------------------------------------------------------------------------------------------
#ifndef FIVEWAYDRIVER_H
#define FIVEWAYDRIVER_H
#include <QCoreApplication>
#include <execinfo.h>
#include <errno.h>
#include <cxxabi.h>
#include <stdio.h>
#include <signal.h>
#include <stdlib.h>
#include <unistd.h>
class FiveWayDriver : public QObject
{
Q_OBJECT
public:
FiveWayDriver();
public slots:
void processFiveWayButton();
private slots:
void upButtonClicked();
void toggleTimer();
private:
QTimer *m_Timer;
};
#endif // FIVEWAYDRIVER_H
-------------------------------------------------------------------------------------------------------
What I am expecting to see it the QTimer calling processFiveWayButton() and that function calling upButtonClicked() but this is what actually comes out of the backtrace print...
Process /home/nrogers/dev/projects/DbusBreadboardDesktopBuild/Debug/FiveWayDriver/FiveWayDriver got signal 11
stack trace:
/home/nrogers/dev/projects/DbusBreadboardDesktopBuild/Debug/FiveWayDriver/FiveWayDriver() [0x40303e]
/lib/x86_64-linux-gnu/libc.so.6 : + 0x364a0
/home/nrogers/dev/projects/DbusBreadboardDesktopBuild/Debug/FiveWayDriver/FiveWayDriver() [0x403933]
/home/nrogers/dev/projects/DbusBreadboardDesktopBuild/Debug/FiveWayDriver/FiveWayDriver() [0x403a18]
/home/nrogers/dev/projects/DbusBreadboardDesktopBuild/Debug/FiveWayDriver/FiveWayDriver() [0x404e19]
/home/nrogers/Qt5.2.0/5.2.0/gcc_64/lib/libQt5Core.so.5 : QMetaObject::activate(QObject*, int, int, void**) + 0x2d1
/home/nrogers/Qt5.2.0/5.2.0/gcc_64/lib/libQt5Core.so.5 : QTimer::timerEvent(QTimerEvent*) + 0x32
/home/nrogers/Qt5.2.0/5.2.0/gcc_64/lib/libQt5Core.so.5 : QObject::event(QEvent*) + 0x69
/home/nrogers/Qt5.2.0/5.2.0/gcc_64/lib/libQt5Core.so.5 : QCoreApplication::notify(QObject*, QEvent*) + 0x3d
/home/nrogers/Qt5.2.0/5.2.0/gcc_64/lib/libQt5Core.so.5 : QCoreApplication::notifyInternal(QObject*, QEvent*) + 0x84
/home/nrogers/Qt5.2.0/5.2.0/gcc_64/lib/libQt5Core.so.5 : QTimerInfoList::activateTimers() + 0x50c
/home/nrogers/Qt5.2.0/5.2.0/gcc_64/lib/libQt5Core.so.5 : + 0x2d47ed
/lib/x86_64-linux-gnu/libglib-2.0.so.0 : g_main_context_dispatch + 0x133
/lib/x86_64-linux-gnu/libglib-2.0.so.0 : + 0x48060
/lib/x86_64-linux-gnu/libglib-2.0.so.0 : g_main_context_iteration + 0x34
/home/nrogers/Qt5.2.0/5.2.0/gcc_64/lib/libQt5Core.so.5 : QEventDispatcherGlib::processEvents(QFlags<QEventLoop::ProcessEventsFlag>) + 0xc3
/home/nrogers/Qt5.2.0/5.2.0/gcc_64/lib/libQt5Core.so.5 : QEventLoop::exec(QFlags<QEventLoop::ProcessEventsFlag>) + 0xcb
/home/nrogers/Qt5.2.0/5.2.0/gcc_64/lib/libQt5Core.so.5 : QCoreApplication::exec() + 0x7e
/home/nrogers/dev/projects/DbusBreadboardDesktopBuild/Debug/FiveWayDriver/FiveWayDriver() [0x4030db]
/lib/x86_64-linux-gnu/libc.so.6 : __libc_start_main + 0xed
/home/nrogers/dev/projects/DbusBreadboardDesktopBuild/Debug/FiveWayDriver/FiveWayDriver() [0x4028f9]
Is there a way to get what I want (ie. QTimer calling processFiveWayButton() and that function calling upButtonClicked())? Thanks!
Nate
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