SQLite vtable bug repro

main.c

// Copyright 2019 Google LLC.
// SPDX-License-Identifier: Apache-2.0

#include <sqlite3.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

typedef struct Cursor {
  sqlite3_vtab_cursor c;
  int index;
} Cursor;

int create(sqlite3* xdb, void* x, int y, const char* const* z, sqlite3_vtab** v,
           char** a) {
  int res = sqlite3_declare_vtab(xdb, "CREATE TABLE x(a INT);");
  if (res != SQLITE_OK) return res;
  *v = malloc(sizeof(sqlite3_vtab));
  return SQLITE_OK;
}

int destroy(sqlite3_vtab* v) {
  free(v);
  return SQLITE_OK;
}
int open(sqlite3_vtab* v, sqlite3_vtab_cursor** c) {
  *c = malloc(sizeof(Cursor));
  memset(*c, 0, sizeof(Cursor));
  return SQLITE_OK;
}
int bestindex(sqlite3_vtab* v, sqlite3_index_info* i) {
  int c = 0;
  for (int j = 0; j < i->nConstraint; ++j) {
    if (i->aConstraint[j].usable)
      i->aConstraintUsage[j].argvIndex = ++c;
  }
  return SQLITE_OK;
}
int filter(sqlite3_vtab_cursor* c, int x, const char* y, int z,
           sqlite3_value** v) {
  return SQLITE_OK;
}
int close(sqlite3_vtab_cursor* c) {
  free(c);
  return SQLITE_OK;
}
int next(sqlite3_vtab_cursor* c) {
  Cursor* cursor = (Cursor*)c;
  cursor->index++;
  return SQLITE_OK;
}
int eof(sqlite3_vtab_cursor* c) {
  Cursor* cursor = (Cursor*)c;
  return cursor->index >= 2;
}
int column(sqlite3_vtab_cursor* c, sqlite3_context* a, int col) {
  Cursor* cursor = (Cursor*)c;
  if (cursor->index % 2 == 0) {
    sqlite3_result_int(a, cursor->index);
  } else {
    sqlite3_result_null(a);
  }
  return SQLITE_OK;
}
int callback(void* noop, int c, char** col, char** name) {
  for (int i = 0; i < c; ++i) {
    printf("%s ", col[i]);  
  }
  printf("\n");
  return SQLITE_OK;
}
int main(int argc, char** argv) {
  sqlite3* db = NULL;
  sqlite3_initialize();
  sqlite3_open(":memory:", &db);

  sqlite3_module* module = malloc(sizeof(sqlite3_module));
  memset(module, 0, sizeof(*module));
  module->xCreate = &create;
  module->xConnect = &create;
  module->xDisconnect = &destroy;
  module->xDestroy = &destroy;
  module->xOpen = &open;
  module->xClose = &close;
  module->xBestIndex = &bestindex;
  module->xFilter = &filter;
  module->xNext = &next;
  module->xEof = &eof;
  module->xColumn = &column;

  int res = sqlite3_create_module_v2(db, "Z", module, NULL, NULL);
  char* err;
  sqlite3_exec(db, "SELECT * FROM Z WHERE a = 0 or a = 1", &callback, NULL, &err);
  return 0;
}