Question

I have some file writing code that works as expected, but prints an error on Debug mode, no output errors in Release.

Code:

#include <iostream>
#include <string>
#include <fstream>
#include <sstream>

using namespace std;

int main (int argc, char * const argv[]) {
    string cppfilename; 
    std::cout << "Please enter the filename to create: ";

    while ( cppfilename == "" ) {
        getline(cin, cppfilename);    // error occurs here
    }

    cppfilename += ".txt";
    ofstream fileout;
    fileout.open( cppfilename.c_str() );
    fileout << "Writing this to a file.\n"; 
    fileout.close();

    return 0;
}

Debug Output:

Please enter the filename to create: Running…
myfile
FileIO(5403) malloc: *** error for object 0xb3e8: pointer being freed was not allocated
*** set a breakpoint in malloc_error_break to debug
Created: myfile.txt

Release Output:

FileIO implementation C++
Please enter the filename to create: Running…
myfile
Created: myfile.txt

Aside from not checking for the file descriptor being open (for simplicity) what is wrong with this code?

Update: I broke the code down to the following and it still errors:

 string cppfilename; 
 getline(cin, cppfilename);    // error here

Answer 1

This looks to be another case of _GLIBCXX_DEBUG being broken with gcc 4.2 on Mac OS X.

Your best options look to be to drop _GLIBCXX_DEBUG or to switch to gcc 4.0.