Greetings, 
my program exits with the code 3. No error messages, no exceptions, and the exit is not initiated by my code.
The problem occurs when I am trying to read extremely long integer values from a text file (the text file is present and correctly opened, with successful prior reading).  
I am using very large amounts of memory (in fact, I think that this might be the cause, as I am nearly sure I go over the 2GB per process memory limit). I am also using the GMP (or, rather, MPIR) library to multiply bignums. I am fairly sure that this is not a file I/O problem as I got the same error code on a previous program version that was fully in-memory.
System:
MS Visual Studio 2008
MS Windows Vista Home Premium x86
MPIR 2.1.0 rc2
4GB RAM
Where might this error code originate from?
EDIT: this is the procedure that exits with the code
void condenseBinSplitFile(const char *sourceFilename, int partCount){
//condense results file into final P and Q
std::string tempFilename;
std::string inputFilename(sourceFilename);
std::string outputFilename(BIN_SPLIT_FILENAME_DATA2);
mpz_class *P = new mpz_class(0);
mpz_class *Q = new mpz_class(0);
mpz_class *PP = new mpz_class(0);
mpz_class *QQ = new mpz_class(0);
FILE *sourceFile;
FILE *resultFile;
fpos_t oldPos;
int swapCount = 0;
while (partCount > 1){
    std::cout << partCount << std::endl;
    sourceFile = fopen(inputFilename.c_str(), "r");     
    resultFile = fopen(outputFilename.c_str(), "w");
    for (int i=0; i<partCount/2; i++){
        //Multiplication order:
        //Get Q, skip P
        //Get QQ, mul Q and QQ, print Q, delete Q
        //Jump back to P, get P
        //Mul P and QQ, delete QQ
        //Skip QQ, get PP
        //Mul P and PP, delete P and PP
        //Get Q, skip P
        mpz_inp_str(Q->get_mpz_t(), sourceFile, CALC_BASE);
        fgetpos(sourceFile, &oldPos);
        skipLine(sourceFile);
        skipLine(sourceFile);
        //Get QQ, mul Q and QQ, print Q, delete Q
        mpz_inp_str(QQ->get_mpz_t(), sourceFile, CALC_BASE);      
        (*Q) *= (*QQ);
        mpz_out_str(resultFile, CALC_BASE, Q->get_mpz_t());
        fputc('\n', resultFile);
        (*Q) = 0;
        //Jump back to P, get P
        fsetpos(sourceFile, &oldPos);
        mpz_inp_str(P->get_mpz_t(), sourceFile, CALC_BASE);
        //Mul P and QQ, delete QQ
        (*P) *= (*QQ);
        (*QQ) = 0;
        //Skip QQ, get PP
        skipLine(sourceFile);
        skipLine(sourceFile);
        mpz_inp_str(PP->get_mpz_t(), sourceFile, CALC_BASE); 
        //Mul P and PP, delete PP, print P, delete P             
        (*P) += (*PP);
        (*PP) = 0;
        mpz_out_str(resultFile, CALC_BASE, P->get_mpz_t());
        fputc('\n', resultFile);
        (*P) = 0;
    }
    partCount /= 2;
    fclose(sourceFile);
    fclose(resultFile);
    //swap filenames
    tempFilename = inputFilename;
    inputFilename = outputFilename;
    outputFilename = tempFilename;
    swapCount++;
}
delete P;
delete Q;
delete PP;
delete QQ;
remove(BIN_SPLIT_FILENAME_RESULTS);
if (swapCount%2 == 0)
    rename(sourceFilename, BIN_SPLIT_FILENAME_RESULTS);
else
    rename(BIN_SPLIT_FILENAME_DATA2, BIN_SPLIT_FILENAME_RESULTS);
}