c - sqlite3_bind_blob 什么时候释放内存是安全的？

Question

我有这样的工作代码:

const char sql[] = "INSERT INTO test (pk, geom) VALUES (?, ?)";
sqlite3_stmt *stmt;
sqlite3_prepare_v2 (handle, sql, strlen (sql), &stmt, NULL);

for (...) {
        sqlite3_reset (stmt);
        sqlite3_clear_bindings (stmt);
        int blob_size = ..;
        unsigned char *blob = malloc(blob_size);
        sqlite3_bind_int64 (stmt, 1, pk);
        sqlite3_bind_blob (stmt, 2, blob, blob_size, free);
        sqlite3_step (stmt);
}

我想知道是否可以在循环的每一步都不分配和释放？如果我将 SQLITE_STATIC 而不是 free 传递给 sqlite3_bind_blob并在循环结束后调用 free 此代码是否仍然有效？

const char sql[] = "INSERT INTO test (pk, geom) VALUES (?, ?)";
sqlite3_stmt *stmt;
sqlite3_prepare_v2 (handle, sql, strlen (sql), &stmt, NULL);
int capacity = 1024;
unsigned char *blob = malloc(capacity);

for (...) {
        sqlite3_reset (stmt);
        sqlite3_clear_bindings (stmt);
        int blob_size = ..;
        if (capacity < blob_size) {
           blob = realloc(blob, blob_size);
           capacity = blob_size;
        }
        sqlite3_bind_int64 (stmt, 1, pk);
        sqlite3_bind_blob (stmt, 2, blob, blob_size, SQLITE_STATIC);
        sqlite3_step (stmt);
}
free(blob);

Answer 1

使用 SQLITE_STATIC 要求该值在语句可能访问它时保持有效。

您的代码应该是有效的；但可以肯定的是，将对 sqlite3_clear_bindings() 的调用(以及重置)移动到循环的末尾。