Presmerovanie stderr

void saveCtxToFileForTest(BPU_T_Mecs_Ctx *globalCtx, BPU_T_Mecs_Ctx *threadCtx) {
    FILE *fp1, *fp2;

    int old_stderr = dup(fileno(stderr));  // Preserve original file descriptor for stdout.

    // save result to "file1"
    fp1 = freopen("file1", "w", stderr);  // Open new stdout
    BPU_printGf2SparseQcMatrix(&(globalCtx->code_ctx->code_spec->qcldpc->Q_sparse)); // this function prints to stderr by default
    fclose(fp1);

    // save result to "file2"
    fp1 = freopen("file2", "w", stderr);  // Open new stdout
    BPU_printGf2SparseQcMatrix(&(threadCtx->code_ctx->code_spec->qcldpc->Q_sparse));  // this function prints to stderr by default
    fclose(fp1);

    // close file descriptors and redirect output back to stderr
    dup2(old_stderr, STDERR_FILENO); // Vratime povodny deskriptor na dvojku (STDERR_FILENO)
    fp2 = fdopen(STDERR_FILENO, "w");   // Open old stdout as a stream XXX Otvorime dvojku, lebo odtial berie konzola vystup
    // fclose(stderr);    // Equivalent to fclose(fp1); XXX Zavreli sme ho na riadku 14
    stderr = fp2;      // Assign fp2 to stdout

    close(old_stderr);   // Close the file descriptor so pipes work sanely
}