所以我正在进行一项特定的编程任务，我认为需要使用我不熟悉的malloc()函数。我的理解是，如果你使用malloc()，你必须在使用它时释放内存，否则你最终可能会遇到奇怪的行为。我想知道这是否是为什么我每隔一段时间就会得到一个总线10运行时错误？
任务是写一个摇滚剪刀纸游戏，这就是我想出来的。
#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#include <string.h>
char* getUserChoice()
{
/* Prompt the user "Enter rock, paper, or scissors: " and return
the string they enter */
printf("Enter rock, paper, or scissors: ");
char * uChoice = malloc(sizeof(char) * 128);
scanf("%s", uChoice);
return uChoice;
}
char* getComputerChoice()
{
srand (time(NULL));
/* get a pseudo-random integer between 0 and 2 (inclusive) */
int randChoice = rand() % 3;
char * cpuChoice = malloc(sizeof(char) * 128);
/* If randChoice is 0, return "rock", otherwise if randChoice is 1,
return "paper", and if randChoice is 2, return "scissors". */
if (randChoice == 0)
cpuChoice = "rock";
else if (randChoice == 1)
cpuChoice = "paper";
else
cpuChoice = "scissors";
return cpuChoice;
}
char* compare(char* choice1, char* choice2)
{
/* Implement the logic of the game here. If choice1 and choice2
are equal, the result should be "This game is a tie."
Make sure to use strcmp for string comparison.*/
char * cmpChoice = malloc(sizeof(char) * 128);
int comparedValue = strcmp(choice1,choice2);
if (comparedValue == 0)
cmpChoice = "This game is a tie.";
else
{
if ((strcmp(choice1, "rock") == 0 && strcmp(choice2, "paper") == 0) ||
(strcmp(choice1,"paper") == 0 && strcmp(choice2, "scissors") == 0) ||
(strcmp(choice1, "scissors") == 0 && strcmp(choice2, "rock") == 0))
cmpChoice = strcat(choice2, " wins");
else
strcat(choice1, " wins);
}
return cmpChoice;
}
int main(int argc, char** argv)
{
char *userChoice, *computerChoice, *outcome;
userChoice = getUserChoice();
computerChoice = getComputerChoice();
outcome = compare(userChoice, computerChoice);
printf("You picked %s.\n", userChoice);
printf("Computer picked %s\n", computerChoice);
printf("%s\n", outcome);
return 0;
}
我所描述的奇怪行为有时输出将是这样的
Enter rock, paper, or scissors: paper
You picked paper wins.. // why is it saying "You picked paper wins.."
Computer picked rock
paper wins.
和其他没有重新编译的时间将是
Enter rock, paper, or scissors: scissors
Bus error: 10 // possibly due to not calling free()?
如果有人能帮助我理解在返回指针之前我将如何释放我分配的内存。显然，使用字符串会更容易，但要求使用char *类型。
感谢您提供的任何帮助或见解。
使用更新的代码进行编辑
#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#include <string.h>
char* getUserChoice()
{
/* Prompt the user "Enter rock, paper, or scissors: " and return
the string they enter */
printf("Enter rock, paper, or scissors: ");
char * uChoice = malloc(sizeof(char) * 128);
scanf("%s", uChoice);
return uChoice;
}
char* getComputerChoice()
{
srand (time(NULL));
/* get a pseudo-random integer between 0 and 2 (inclusive) */
int randChoice = rand() % 3;
char * cpuChoice = malloc(sizeof(char) * 128);
/* If randChoice is 0, return "rock", otherwise if randChoice is 1,
return "paper", and if randChoice is 2, return "scissors". */
if (randChoice == 0)
strcpy(cpuChoice, "rock");
else if (randChoice == 1)
strcpy(cpuChoice, "paper");
else
strcpy(cpuChoice, "scissors");
return cpuChoice;
}
char* compare(char* choice1, char* choice2)
{
/* Implement the logic of the game here. If choice1 and choice2
are equal, the result should be "This game is a tie."
Make sure to use strcmp for string comparison.*/
char * cmpChoice = malloc(sizeof(char) * 128);
int comparedValue = strcmp(choice1,choice2);
if (comparedValue == 0)
strcpy(cmpChoice, "This game is a tie.");
else
{
if ((strcmp(choice1, "rock") == 0 && strcmp(choice2, "paper") == 0) ||
(strcmp(choice1,"paper") == 0 && strcmp(choice2, "scissors") == 0) ||
(strcmp(choice1, "scissors") == 0 && strcmp(choice2, "rock") == 0))
{
strcat(cmpChoice, choice2);
strcat(cmpChoice, " wins");
}
else
{
strcat(cmpChoice, choice1);
strcat(cmpChoice, " wins.");
}
}
return cmpChoice;
}
int main(int argc, char** argv)
{
char *userChoice, *computerChoice, *outcome;
userChoice = getUserChoice();
computerChoice = getComputerChoice();
outcome = compare(userChoice, computerChoice);
printf("You picked %s.\n", userChoice);
printf("Computer picked %s\n", computerChoice);
printf("%s\n", outcome);
return 0;
}
所以，非常感谢每个人的评论。我已经在代码上修复了一些问题，它似乎正在编译并运行而没有错误。现在，我正在试图找出何时free() malloced内存。我显然无法在返回后释放它，但我需要返回值。
我会将其复制到char然后释放分配的原始内存吗？
再次感谢
答案 0 :(得分：0)
您不需要使用malloc。只需将char指针传递给方法，而不是返回一个。
void getUserChoice(char * choice)
{
/* Prompt the user "Enter rock, paper, or scissors: " and return
the string they enter */
printf("Enter rock, paper, or scissors: ");
scanf("%s", choice);
}
然后在主要内部使用它...
char uChoice[128];
getUserChoice(uChoice);
答案 1 :(得分：0)
You picked paper wins.. // why is it saying "You picked paper wins.."
在char* compare(char* choice1, char* choice2)中，你对选择1和选择2执行strcat（）
因此在打印之前会修改userChoice的内容。
同样在char* getComputerChoice()中，你应该strcpy（）或strncpy（）将字符串复制到新的malloced空间，而不是=，后者是分配字符串文字，这就是为什么有时你会出现Segmentation fault ，因为如果计算机获胜，你的程序将尝试strcat choice2，这是不允许字符串文字。
答案 2 :(得分：0)
虽然你应该免费使用malloc内存，是的，问题就在这里
if（randChoice == 0）
cpuChoice = "rock"; //use strcpy(cpuChoice,"rock");
else if (randChoice == 1)
cpuChoice = "paper"; // strcpy(cpuChoice,"paper");
else
cpuChoice = "scissors"; // strcpy(cpuChoice,"scissors");
答案 3 :(得分：0)
由于每次跑步都会优先玩游戏一次。你可以使用while循环你可以从用户那里继续输入或不使用开关等。下面我只包括while循环。
int main(int argc, char** argv)
{
char *userChoice, *computerChoice, *outcome;
while(1)
{
userChoice = getUserChoice();
printf("You picked %s.\n", userChoice);
computerChoice = getComputerChoice();
printf("Computer picked %s\n", computerChoice);
outcome = compare(userChoice, computerChoice);
printf("%s\n", outcome);
}
return 0;
}
在这种情况下，您的代码会调用malloc n次，这将导致不必要的内存创建。如果使用很多，最终可能会使程序崩溃，因为你还没有释放内存。
所以释放内存总是有益的，也是更好的编码方式。
对于未定义的行为，使用相同的userchoice指针并与函数
中的结果连接 char* compare(char* choice1, char* choice2)
要避免这种情况，你可以移动你的“printf（”你选择％s。\ n“，userChoice）” 在“userChoice = getUserChoice（）;”之后如上所示在代码中
并使用strcpy（）复制函数中的字符串char * getComputerChoice（）