gcc 2.95: strange results with strings

[Patrick Ogay]

I never trusted string handling in C/C++, besides I'm coming from PL/I :-)
But now I seem to have a fundamental problem:
gcc version 2.95.3-6 / win2k

Until now I was convinced that:
string a("blabla");
const char *ptr = a.data(); 

I never realized problems with that until yesterday.
I can not say it doesn't work, but sometimes the results are undefinded, seems to be a initialization problem.

May be, you guys, can give my a few hints.

Patrick

//  Routine for internet, Robert told me, never having problems with it
//
std::string GetIniSetting(INIFile &theINI, const char *section, const char *key, const char *defaultval)
{
    std::string result(defaultval);
        if (key==0) return result;
    INIFile::iterator iSection = theINI.find(std::string(section));
    if(iSection != theINI.end())
    {
        INISection::iterator apair = iSection->second.find(std::string(key));
        if(apair != iSection->second.end()){
            result = apair->second;
            _log("+1 GetIniSet: \\%s\\\n", apair->second.data());  01]  // pog test
                }
    }
==>    // ---- pog trying to correct the strings...
    string mod_string;
    mod_string ="                                                         "; // some tests
    mod_string ="";
    int pos=result.find(";");
        mod_string = result.substr(0,pos); // even tried + "\0";
    _log("+2 modstring \\%s\\ %i\n", mod_string.data(),mod_string.length());
        // ---- pog end
    return result;
}

Test-Output:
+1 GetIniSet: \yes;\                 ok
+2 modstring \yes\ 3                 correction ok
+1 GetIniSet: \scan;\
+2 modstring \scan\ 4
+1 GetIniSet: \[a,A,p,P,g,G][P][0-9]{5};\
+2 modstring \[a,A,p,P,g,G][P][0-9]{5}\ 24
+1 GetIniSet: \[.]doc;\
+2 modstring \[.]doc\ 6
+1 GetIniSet: \network;\              string ok
+2 modstring \networkdfasdf\ 7        correction makes string even wrong! length of string ok.
+1 GetIniSet: \\copy_place; \
+2 modstring \\copy_place\ 11
+1 GetIniSet: \log01.txt;\
+2 modstring \log01.txtasdf\ 9
+1 GetIniSet: \2002;\
+2 modstring \2002\ 4
+1 GetIniSet: \02;                                                      \
+2 modstring \02nth\ 2
+1 GetIniSet: \15;\
+2 modstring \15y\ 2
+1 GetIniSet: \02;v\
+2 modstring \02lv\ 2
+1 GetIniSet: \5;lv\             01]  cases I want to correct  
+2 modstring \5_lv\ 1                 string always wrong but lenght ok.

// logging routine
void _log(const char *str, ...){
  va_list         args;
  va_start    (   args,   str);

  static FILE *outstream;
  static int open = 0;
  if (open==0){
    outstream = fopen("log01.txt", "w"); open = 1;
  }
 
  vfprintf(outstream,str,args);
  fflush(outstream);
  va_end  (args);
}

[Anonymous]

You should use
const char *ptr = a.c_str();

This is guaranteed to return a pointer to a C style string (NUL terminated character array).

[Patrick Ogay]

the example works with c_str() !!!!

I think all problems I had, (particularly with the template)  came form the wrong conversion with a.data().

thank you very much!

Patrick