Thread: Wierd POD type error

../Source/Game/Fleet.cpp: In member function `const bool Fleet::Save(FILE*)':
../Source/Game/Fleet.cpp:82: warning: cannot pass objects of non-POD type `
const struct std::string' through `...'; call will abort at runtime

I have no clue what a POD type struct is or a `...' call.
I'm asumming the ... call is the %-substitution in printf()
I might be wrong..

Code:

const bool Fleet::Save( FILE *fd )
{
        fprintf( fd ,
                                "\n[%s-Fleet_%s]\n"
                      "posx = %f\n"
                                "posy = %f\n"
                                "origin = %s\n"
                      "destx = %f\n"
                                "desty = %f\n"
        , species.c_str() , name.c_str() , position.x , position.y , origin.c_str() , dest.x , dest.y );
        if( !destination.empty() )
                fprintf( fd , "destination = %s\n" , destination.c_str() );

        int     i = 0;
        for( vector<Vessel *>::iterator it = begin() ; it != end() ; ++it )
                for( int j = 0 ; j < (*it)->GetCount() ; j++ )
                        fprintf( fd , "%d = %s\n" , i++ , (*it)->vesselClass ); //LINE 82 with the error

        return true;
}

Any clue what's happining?
I can provide any part of the code..and if you want you can get it from sourceforge.. Borqueror is GPLed (I'm porting it back to Linux, even though it's supposed to work)

Thanks

Thank you

That worked
Could you tell me why though?
I hate leeching, and want to understand what actually happened there

Thanks

The printf and friends (like fprintf, scanf, sprintf and others) use the elipsis operator to pass parameters. This means that things are parsed using vargs macros (or however the compiler has it implemented).

Function declaration is something like

Code:

fprintf(FILE *fp, char *format, ...) { /* important stuff */ }

This way it can read the format string and depending on content, read more from the stack. This, IMHO, is horrible and very error prone.

You can accidently do this:
printf("%s%s%s%s", foo) and then function will try to read 4 pointers on the stack and without safety check can easily behave in a very bad way causing all sorts of maladies.

This is useful when you do not know how many parameters are being passed to a function. It expects simply types and passing it a class (std::string in this case) gets it confusied when it was looking for a pointer to convert to char* in this case.

This is mixing old C and C++ and, depending which language diety you follow, can be considered very bad form.

However if taking care and calling the correct conversion functions like .c_str() in case of std::string, you can use old-school C functions with C++ classes.

Ideally you should open an ofstream and pipe things out using << operator. But that is just a suggestion.

Hmm.. that makes sens.. But I'm stuck with the same error in a different part of the code.
ofstream doesn't exist in Linux I beleive

Code:

#include "stdafx.h"

#include "include.h"
#include "extreal.h"
#include "newran.h"

#ifdef use_namespace
using namespace NEWRAN;
#endif
using namespace std;

#define al_trace printf

void Histogram(Random* rx, int n)          // draw histogram with n obsv
{
   int i,j; int count[20];
   Real* a = new Real[n];
   for (i = 0; i < n; i++) a[i] = rx->Next();
   Real amax = a[0]; Real amin = a[0]; Real mean = a[0]; Real sd = 0;
   for (i = 1; i < n; i++)
   {
      if (amin > a[i]) amin = a[i]; else if (amax < a[i]) amax = a[i];
      mean += a[i];
   }
   mean /= n;
   for (i = 0; i < 20; i++) count[i]=0;
   for (i = 0; i < n; i++)
   {
     Real rat= (amax != amin) ? (a[i] - amin)/(amax - amin) : 1.0;
     j = (int)( 19.999 * rat ); count[j]++;
     Real diff = a[i] - mean; sd += diff*diff;
   }
   sd = sqrt(sd/(n-1));
   j = 0;
   for (i = 0; i < 20; i++) { if (j < count[i]) j = count[i]; }
   if (j > 70) { for (i = 0; i < 20; i++) count[i] = (int)((70L*count[i])/j); }

   al_trace( "\n" );
   for (i = 0; i < 20; i++)
        {
                al_trace( "\n|" );
                for (j = 1; j < count[i]; j = j+1)
                        al_trace( "*" );
        }
   al_trace( "\n%s\np. mean = %9f, p. var = %9f\ns. mean = %9f, s. var = %9f\n" ,
                rx->Name() , rx->Mean() , rx->Variance() , mean , sd * sd ); //LINE 50

   delete a;
}

void Hist(Random* rx, int n , const int cnt )          // draw histogram with n obsv
{
   int i,j; int *count = new int[cnt];
   Real* a = new Real[n];
   for (i = 0; i < n; i++) a[i] = rx->Next();
   Real amax = a[0]; Real amin = a[0]; Real mean = a[0]; Real sd = 0;
   for (i = 1; i < n; i++)
   {
      if (amin > a[i]) amin = a[i]; else if (amax < a[i]) amax = a[i];
      mean += a[i];
   }
   mean /= n;
   for (i = 0; i < cnt ;  i++) count[i]=0;
   for (i = 0; i < n; i++)
   {
     Real rat= (amax != amin) ? (a[i] - amin)/(amax - amin) : 1.0;
     j = (int)( (cnt - 0.001) * rat ); count[j]++;
     Real diff = a[i] - mean; sd += diff*diff;
   }
   sd = sqrt(sd/(n-1));
   j = 0;
   for (i = 0; i < cnt; i++) { if (j < count[i]) j = count[i]; }
   if (j > 70) { for (i = 0; i < cnt; i++) if( count[i] )       count[i] = (int)((70L*count[i])/j); }

   al_trace( "\n" );
   for (i = 0; i < cnt; i++)
        {
                al_trace( "\n%02d|" , i );
                for (j = 1; j < count[i] ; j = j+1)
                        al_trace( "*" );
        }
   al_trace( "\n%s\np. mean = %9f, p. var = %9f\ns. mean = %9f, s. var = %9f\n" ,
                rx->Name() , rx->Mean() , rx->Variance() , mean , sd * sd );//LINE 87

        delete count;
   delete a;
}

The code that makes the ExtReal class is

Code:

// extreal.h ----------------------------------------------------------


#ifndef EXTREAL_LIB
#define EXTREAL_LIB 0

#ifdef use_namespace
namespace NEWRAN { using namespace RBD_COMMON; }
namespace RBD_LIBRARIES { using namespace NEWRAN; }
namespace NEWRAN {
#endif

/************************ extended real class ***************************/

enum EXT_REAL_CODE
   { Finite, PlusInfinity, MinusInfinity, Indefinite, Missing };

class ExtReal   {
   Real value;
   EXT_REAL_CODE c;
public:
   ExtReal operator+(const ExtReal&) const;
   ExtReal operator-(const ExtReal&) const;
   ExtReal operator*(const ExtReal&) const;
   ExtReal operator-() const;
   friend ostream& operator<<( ostream&, const ExtReal& );
   ExtReal(Real v) { c=Finite; value=v; }
   ExtReal(const EXT_REAL_CODE& cx) { c = cx; }
   ExtReal() { c = Missing; }
   Real Value() const { return value; }
   bool IsReal() const { return c==Finite; }
   EXT_REAL_CODE Code() const { return c; }
};

#ifdef use_namespace
}
#endif


#endif

That's the header tell me if you want the source too

The errors I get are

Code:

../Source/Distribution/hist.cpp: In function `void Histogram(Random*, int)':
../Source/Distribution/hist.cpp:50: warning: cannot pass objects of non-POD
   type `class ExtReal' through `...'; call will abort at runtime
../Source/Distribution/hist.cpp:50: warning: cannot pass objects of non-POD
   type `class ExtReal' through `...'; call will abort at runtime
../Source/Distribution/hist.cpp: In function `void Hist(Random*, int, int)':
../Source/Distribution/hist.cpp:87: warning: cannot pass objects of non-POD
   type `class ExtReal' through `...'; call will abort at runtime
../Source/Distribution/hist.cpp:87: warning: cannot pass objects of non-POD
   type `class ExtReal' through `...'; call will abort at runtime

No clue what to do with that

Thanks