fftwf_plan_dft_1d( ... ) with FFTW fails to be executed

Question

The fftwf_plan_dft_1d(...) line of the following function fails in Ubuntu. It is used for doing FFT on a complex vectors of a length of about 4096 numbers.

Please help. TIA

This is C code compiled and run in Ubuntu 18.04. There is no issue of compilation.

extern void cpxfft(fftwf_plan plan, cpx_t *cpx, int n)
{
#ifdef FFTMTX
        mlock(hfftmtx);
#endif
    if (plan==NULL) {
        fftwf_plan_with_nthreads(NFFTTHREAD); /* fft execute in multi threads */
        plan=fftwf_plan_dft_1d(n,cpx,cpx,FFTW_FORWARD,FFTW_ESTIMATE);
        fftwf_execute_dft(plan,cpx,cpx); /* fft */
        fftwf_destroy_plan(plan);
    } else {
        fftwf_execute_dft(plan,cpx,cpx); /* fft */
    }
#ifdef FFTMTX
        unmlock(hfftmtx);
#endif
}

The console displayed the following error messages:

free(): invalid next size (fast)
Aborted (core dumped)