foo.cc: In function ‘void fft::solve(int, int)’:
foo.cc:53:9: warning: ‘void* memset(void*, int, size_t)’ clearing an object of non-trivial type ‘struct fft::complex’; use assignment or value-initialization instead [-Wclass-memaccess]
   53 |   memset(res, 0, sizeof(res));
      |   ~~~~~~^~~~~~~~~~~~~~~~~~~~~
foo.cc:9:8: note: ‘struct fft::complex’ declared here
    9 | struct complex {
      |        ^~~~~~~