Lesser known tricks, quirks and features of C
Great read, and lead me to "When VLA in C doesn't smell of rotten eggs" https://blog.joren.ga/vla-usecases and this:  int n = 3, m = 4;
  int (*matrix_NxM)[n][m] = malloc(sizeof *matrix_NxM); // `n` and `m` are variables with dimensions known at runtime, not compile time
  if (matrix_NxM) {
      // (*matrix_NxM)[i][j] = ...;
      free(matrix_NxM);
  }

Well, that makes much easier a few things I'm doing atm, really glad I read it.