How to debug with dbg in this case?

[jpn]

How to break at the line which output this warning?

Search where the warning comes from and set a breakpoint there. break <filename:linenum> or break <filename:function>... Refer to the manual of gdb for more info.

[vql]

Sorry, the warning output from file Coin library in Linux (.o), not in source .cpp. Please help me.

[jacek]

Sorry, the warning output from file Coin library in Linux (.o), not in source .cpp. Please help me.

Could you post the exact error message?

[vql]

Ok. Because my program is very big, I can't manage errors from my program.
I'm programming with Coin.
I declare a SbBox2f (a, b). Because there are problems about computing, so a & b can negative. If I use this SbBox2f, class SbBox2f (of Coin library) output warning : "Coin warning in SbBox2f::setBounds(): The bound will give the box negative area."

This warning is very dangerous, it cause my program will not run exactly.
Do you know in my program, there are alot places where I declare SbBox2f as above?

How to I know, I have the problem at which line?
Thanks.

[wysota]

Set a breakpoint on SbBox2f::setBounds in the debugger and check each call for negative values. When you encounter them, simply display the backtrace and you'll know where it happens.

[vql]

I have problem about command break (set breakpoint) of gdb.

If I have functions:
void MyClass::test1(QString){ //... }
void MyClass::test2(const QString&){ //... }

When I set breakpoint on test1: break MyClass::test1(QString), it effect.
But when I set breakpoint on test2: break MyClass::test2(const QString&), it doesn't effect.

Thanks.

[vql]

I tried to break on QString ( const QString & other ).

gdb ./myapp
break QString::QString (const QString &)
run

gdb ./myapp
break QString::QString (const QString &)
run

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It can't break on this function (specially on functions have parameter contain keyword const).

Please help me. Thanks.

[wysota]

How about just "break QString::QString"? Or "break QString::QString(const QString&)" (without the space) ?

You can enter "break QString::" and press the tab key to get a list of all methods defined for QString. You can then find the one you seek.

[vql]

How to gdb know functions of QString because QString in Qt's library? So I think in this case, if press Tab, it can't list of all methods defined for QString.

Why do you try to break on QString::QString(const QString&) in examples?

Try it & help me.

[wysota]

How to gdb know functions of QString because QString in Qt's library?

GDB knows how to resolve symbols from the binary it controls and its dependencies.

So I think in this case, if press Tab, it can't list of all methods defined for QString.

You can list methods which are actually seen (used) by your application.

Why do you try to break on QString::QString(const QString&) in examples?

I think the question is why do you try to do it...

[vql]

You answered:

Set a breakpoint on SbBox2f::setBounds in the debugger and check each call for negative values. When you encounter them, simply display the backtrace and you'll know where it happens.

I tried break on SbBox2f::setBound(const SbVec2f&, const SbVec2f&) but it not effect.

Because I think Coin or Qt, they're the same. So I tried on Qt' library with QString.
I tried on QString::QString(QChar), it have effect.
But I tried on QString::QString(const QString&), it don't have effect.

Can you answer this question, wysota??? Please try on your computer before anwer. Thanks.

[wysota]

I tried break on SbBox2f::setBound(const SbVec2f&, const SbVec2f&) but it not effect.

Do you use that method in your app? If not (which means that it is used internally), do you have a debug version of libraries you use compiled? You have to compile in debug mode and link with debug libraries to have access to all symbols from within the debugger.

I tried on QString::QString(QChar), it have effect.
But I tried on QString::QString(const QString&), it don't have effect.

Can you answer this question, wysota??? Please try on your computer before anwer. Thanks.

As I already said, you don't have access to QString::QString(const QString&) because you don't use it in your application.

Try debugging this one:

#include <QString>
int main(){
  QString x  ="xxx";
  QString y(x); // here the copy constructor is used
  return 0;
}

#include <QString>
int main(){
  QString x  ="xxx";
  QString y(x); // here the copy constructor is used
  return 0;
}

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You'll notice that QString::QString(const QString &) will be among symbols available (remember to compile your app in debug mode). If you don't have a debug version of Qt compiled (and linked to the application), you'll only receive symbols defined for your executable and used by it.

(gdb) break QString<tab>
QString                           QString::QString(char const*)
QString::QString(QString const&)  QString::~QString()

(gdb) break QString<tab>
QString                           QString::QString(char const*)
QString::QString(QString const&)  QString::~QString()

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