我已经为此工作了几个小时。我完全被难住了。
这是CS113的实验室。
如果用户在程序（二进制计算器）结束时选择继续，我们需要使用goto语句来到达程序的顶部。
但是，我们还需要释放所有分配的内存。
这两件事似乎不相容。如果我释放了分配的内存，而用户选择继续，那么一切都会变得疯狂。即使这些值被重新初始化，但在这个过程中却不知怎么搞砸了。我真的很抱歉，但我不知道该怎么解释。尽管步骤与第一次跑步相同，但它们最终似乎充满了垃圾。
我的代码在下面。请注意，"空闲分配内存"部分在我的版本中被注释掉了，但我把它留在了这里，这样就不会有混淆了。
编辑：现在可以释放CPU了。目前的版本是有效的。但是，我无法释放我分配的字符串，或者由双链表组成的寄存器。我不能使用的免费函数被注释掉了，并且接近程序的末尾
注意：程序运行得非常好，即使在多次运行中，如果最后内存没有释放。请注意
#include<stdio.h>
#include<stdlib.h>
#include<string.h>
#include"lab9.h"
#include<math.h>
int main()
{
struct cpu_t *cpu = NULL;
top:
if(cpu)
{
free(cpu);
cpu = NULL;
}
cpu = malloc(sizeof(struct cpu_t));
if(!cpu) /* Error check malloc for CPU */
{
printf("Sorry! Malloc failed to allocate space for the CPU!n");
exit(EXIT_FAILURE);
}
struct bit_t *temp1 = cpu->r1_head;
struct bit_t *temp2 = cpu->r2_head;
struct bit_t *temp3 = cpu->r3_head;
/* Setting all flags to 0 by default */
cpu->overflow = 0;
cpu->carry = 0;
cpu->sign = 0;
cpu->parity = 0;
cpu->zero = 0;
char buffer[128];
char unsign; /* Holds a char: 0 for signed, 1 for unsigned */
char *expression = NULL; /* Binary expression */
char *e1 = NULL; /* Holds the first part of the expression */
char op; /* Holds the operand */
char *e2 = NULL; /* Holds the second part of the expression */
char ans; /* y if user wants to continue, else ends program */
int temp = 0; /* Used for printing separating dashes */
int one_count = 0; /* Number of ones in the result */
printf("nPlease enter the word size: ");
fgets(buffer, sizeof(buffer), stdin);
cpu->word_size = atoi(buffer); /* atoi takes a pointer, don't dereference buffer*/
while(cpu->word_size < 1 || cpu->word_size > 64) /* Error check word size */
{
printf("Error: Word size must be between 1 and 64. n");
printf("Enter a new word size: n");
fgets(buffer, sizeof(buffer), stdin);
cpu->word_size = atoi(buffer);
}
printf("Are the values unsigned? [Y/N]: ");
unsign = *fgets(buffer, sizeof(buffer), stdin); /* fgets returns address to data, must be dereferenced */
switch(unsign)
{
case 'y':
case 'Y':
cpu->unsign = 1;
break;
case 'n':
case 'N':
cpu->unsign = 0;
break;
}
printf("Please enter the binary expression: ");
expression = fgets(buffer, sizeof(buffer), stdin); /* Stores expression in string */
e1 = strtok(expression, " "); /* Breaks off first number*/
switch(check_string(cpu, e1)) /* Error check first string */
{
case 1:
printf("Error in input: Length of operand greater than word size. n");
printf("Error in first operand. Retry. n");
goto top;
case 2:
printf("Error in input: Something other than a 1 or 0 entered. n");
printf("Error in first operand. Retry. n");
goto top;
default:
break;
}
e1 = zero_pad(cpu, e1); /* Zero pads first number */
op = *strtok(NULL, " "); /* Operation (+, -, ^, &, |) */
e2 = strtok(NULL, " n"); /* Original string had n at end. Otherwise length would be 1 over actual. */
switch(check_string(cpu, e2)) /* Error check second string */
{
case 1:
printf("Error in input: Length of operand greater than word size. n");
printf("Error in second operand. Retry. n");
goto top;
case 2:
printf("Error in input: Something other than a 1 or 0 entered. n");
printf("Error in second operand. Retry. n");
goto top;
default:
break;
}
e2 = zero_pad(cpu, e2); /* Zero pads second number */
create_r1(cpu, e1);
create_r2(cpu, e2);
create_r3(cpu);
switch(op)
{
case '+':
add_function(cpu);
break;
case '-':
op = '+';
complement(cpu); /* Turns second expression into 2's complement of itself */
add_function(cpu);
break;
case '&':
and_function(cpu);
break;
case '|':
or_function(cpu);
break;
case '^':
xor_function(cpu);
break;
default:
printf("Error in operator. Please retry. n");
goto top;
}
temp1 = cpu->r1_head;
temp2 = cpu->r2_head;
temp3 = cpu->r3_head;
/* Print the first register */
while(temp1)
{
printf("%d", temp1->n);
temp1 = temp1->next;
}
puts("");
/* Print operator */
printf("%cn", op);
/* Print second register */
while(temp2)
{
printf("%d", temp2->n);
temp2 = temp2->next;
}
puts("");
/* Print spacing dashes */
while(temp < (cpu->word_size))
{
printf("-");
temp++;
}
puts("");
/* Print third register (stores answer) */
while(temp3)
{
printf("%d", temp3->n);
temp3 = temp3->next;
}
puts("");
/* Flag handling */
/* Reset temp variables */
temp1 = cpu->r1_head;
temp2 = cpu->r2_head;
temp3 = cpu->r3_head;
/* Flag handling */
if(temp3->n == 1)
{
cpu->sign = 1;
}
while(temp3)
{
if(temp3->n == 1)
{
one_count++;
}
temp3 = temp3->next;
}
if(one_count == 0)
{
cpu->zero = 1;
}
else if(one_count % 2 == 0)
{
cpu->parity = 1;
}
printf("Flags: n");
printf("Overflow: %d n", cpu->overflow);
printf("Carry: %d n", cpu->carry);
printf("Sign: %d n", cpu->sign);
printf("Parity: %d n", cpu->parity);
printf("Zero: %d n", cpu->zero);
printf("Decimal: %d n", find_decimal(cpu));
printf("Do you want to continue? [Y/N] n"); /* If not 'y' or 'Y', close program */
ans = *fgets(buffer, sizeof(buffer), stdin);
/* Reset temps...again */
temp1 = cpu->r1_head;
temp2 = cpu->r2_head;
temp3 = cpu->r3_head;
/* Free all allocated memory */
//delete_list(cpu->r1_head);
//delete_list(cpu->r2_head);
//delete_list(cpu->r3_head);
/* Free zero_string */
//free(e1);
//free(e2);
if(ans == 'Y' || ans == 'y')
{
temp = 0;
goto top;
}
return 0;
}
也许你可以把main的开头改成这样：
int main() {
struct cpu_t *cpu = NULL;
top:
if (cpu) {
free(cpu);
cpu = NULL;
}
cpu = malloc(sizeof(struct cpu_t));