Question

我得到了以下sql_buildup_method ...代码有点脏，但事实并非如此

char *build_up_sql(char *inputName,char *inputMessage)
{
   char firstPartStatement[1064] ="INSERT INTO User (name, msg) VALUES (";
    char *endPartStatement =");";
    char *lightener = "'";  
    char *statement;

strcat(firstPartStatement,lightener);
strcat(firstPartStatement,inputName);
strcat(firstPartStatement,lightener);
strcat(firstPartStatement,",");
strcat(firstPartStatement,lightener);
strcat(firstPartStatement,inputMessage);
strcat(firstPartStatement,lightener);
strcat(firstPartStatement,endPartStatement);

statement = firstPartStatement; 

return statement;

}

void create_input(sqlite3 *handler,char *inputName,char *inputMessage)
{
    char *sql;

    sql = build_up_sql(inputName,inputMessage);
 // sql ="INSERT INTO User (name, msg) VALUES ('Susanne','hi all');";   
    printf("%s\n",sql);
    sqlite3_exec(handler,sql, NULL, NULL, NULL);
}

printf给出输出：INSERT INTO User（name，msg）VALUES（'Susanne'，'hi all'）;这是完全没问题...但是sqlite3_exec忽略它并且没有生成新的数据库输入....如果我离开行 sql =“INSERT INTO用户（名称，消息）VALUES（'Susanne'，'嗨所有'）;“; 在代码中sqlite3_exec工作得很好....也把所有东西放在一个函数中也解决了问题，但这不应该是一个选项.....

Answer 1

这里的问题是你返回一个指向局部变量的指针，这是未定义的行为。当build_up_sql返回时，将重用堆栈中用于局部变量的空间。

最好的解决方案可能是添加一个用于放置字符串的build_up_sql的参数。例如：

char *build_up_sql(char *inputName, char *inputMessage, char *outputSql)
{
    const char firstPartStatement[] = "INSERT INTO User (name, msg) VALUES (";
    const char endPartStatement[] = ");";
    const char lightener[] = "'";

    strcpy(outputSql, firstPartStatement);
    strcat(outputSql,lightener);
    strcat(outputSql,inputName);
    strcat(outputSql,lightener);
    strcat(outputSql,",");
    strcat(outputSql,lightener);
    strcat(outputSql,inputMessage);
    strcat(outputSql,lightener);
    strcat(outputSql,endPartStatement);

    return outputSql;
}

void create_input(sqlite3 *handler, char *inputName, char *inputMessage)
{
    char sql[1024];

    char *sqlstr = build_up_sql(inputName, inputMessage, sql);

    printf("%s\n", sqlstr);
    sqlite3_exec(handler, sqlstr, NULL, NULL, NULL);
}

sqlite3_exec函数忽略sql buildup函数值

1 个答案: