core dump due to string::c_str ()

[puzzlecracker]

Any ideas what may cause that for the string class to core dump?

#0 0x0018de92 in std::string::c_str () from /usr/lib/libstdc++.so.5

 

[Juha Nieminen]

Any ideas what may cause that for the string class to core dump?

#0 0x0018de92 in std::string::c_str () from /usr/lib/libstdc++.so.5

Yes: You are accessing out of bounds somewhere.

Run your program with valgrind.

 

[red floyd]

Any ideas what may cause that for the string class to core dump?

#0  0x0018de92 in std::string::c_str () from /usr/lib/libstdc++.so.5

Come on Puzzlecracker, you should know FAQ 5.8 by now.

There is an error on line 42 of your code.

Post a minimal, compileable example that exhibits the behavior in
question.

 

[puzzlecracker]

  Yes: You are accessing out of bounds somewhere.

  Run your program with valgrind.

Argh, I traced why it happened, and modified my code, removing the
stupidity. Here what I had:

void foo(std::string &str)
{

}


void bar(std::string str)
{
foo(str.c_str());
}


Never used valgrind before. How does it work?

 

[puzzlecracker]

That shouldn't compile. You're trying to bind a non-const reference to
a temporary object (created from the pointer to char you get by calling
the 'c_str()'). That's not allowed. Begin by dialing up the warning
level on your compiler and possibly by disabling extensions you're not
consciously using.

OTOH, there is nothing in this particular code that would cause the
crash. Are you sure you're not trying to access 'c_str' member using an
invalid reference?


It works quite well.

V

Argh, I was passing string in Foo as a const std::string &

I thought c_str() returning const char *...Hmm

 

[James Kanze]

Argh, I was passing string in Foo as a const std::string &

I thought c_str() returning const char *...Hmm

It does, but there is an implicit conversion from char const* to
std::string.

And as Victor said, there's no reason in the code you posted for
anything not to work. You're probably overwriting memory
somewhere else. Valgrind is free; download it and use it.

 

[Juha Nieminen]

Never used valgrind before. How does it work?

You start valgrind giving it your program (and its possible
command-line parameters) as parameter (similarly to how you would use
eg. the "time" command), and it will report about a wide variety of
possible errors in your program.