C 令牌循环段错误问题

Question

对 C 来说有点新，我正在尝试创建一个侦听器，以便用户必须按两次 enter 才能完成输入。然后通过新行和运行通过循环拆分所有数据并通过我的函数发送它们。

我不确定我做错了什么但是当代码中“//segfaulting at loop”下的循环被注释掉时运行很好但是当我取消注释并有我对“// assemble(ftemp);”的调用评论说它是段错误所以我在这里知道它只是不知道是什么。如果有帮助，Valgrind 会在下面说。

感谢高级皮特。

==14639== Invalid read of size 1

==14639==    at 0x4E7754C: ____strtod_l_internal (strtod_l.c:608)

==14639==    by 0x4011F8: main (in /home)

==14639==  Address 0x0 is not stack'd, malloc'd or (recently) free'd

==14639== Process terminating with default action of signal 11 (SIGSEGV)

==14639==  Access not within mapped region at address 0x0

==14639==    at 0x4E7754C: ____strtod_l_internal (strtod_l.c:608)

==14639==    by 0x4011F8: main (in /home)

==14639==  If you believe this happened as a result of a stack

==14639==  overflow in your program's main thread (unlikely but

==14639==  possible), you can try to increase the size of the

==14639==  main thread stack using the --main-stacksize= flag.

==14639==  The main thread stack size used in this run was 8388608.

==14639== HEAP SUMMARY:

==14639==     in use at exit: 0 bytes in 0 blocks

==14639==   total heap usage: 0 allocs, 0 frees, 0 bytes allocated

==14639== All heap blocks were freed -- no leaks are possible

==14639== For counts of detected and suppressed errors, rerun with: -v

==14639== ERROR SUMMARY: 1 errors from 1 contexts (suppressed: 0 from 0)

我的代码：

int main(int argc, char * argv[]) {

printf("Please Enter In Float (Hit Enter Twice To Exicute)\n" );
#define MAXLENGTH 1000
char Input_string[MAXLENGTH];
int ilop = 0;
for(;;++ilop)
{
    Input_string[ilop] = getchar();
    if (ilop > 0 && Input_string[ilop] == '\n' &&
 Input_string[ilop-1] == '\n') break;
}
Input_string[ilop] = 0;

 char *pch;
//  printf ("Splitting string \"%s\" into tokens:\n",Input_string);
pch = strtok (Input_string,"\n");
float ftemp = atof(pch);
//printf("price:, %f\n\n",ftemp);

assemble(ftemp);
 //segfaulting at loop
while (pch != NULL)
{
 pch = strtok (NULL, "\n");
 ftemp = atof(pch);
   printf("price:, %f\n\n",ftemp);
//   assemble(ftemp);
 }


 return 0;
 }

Answer 1

为了扩展 Igal S. 所说的内容，您首先要在循环内设置 strtok，然后使用它，直到循环顶部才检查它。因此，在最后一次迭代中，它将 pch 设置为 NULL，然后将其传递给 atof() 而无需检查。

你需要类似（未测试）的东西：

pch = strtok (Input_string, "\n");
while (pch != NULL)
{
  /* ... */
  pch = strtok (NULL, "\n");
}

Answer 2

存在数组越界访问的可能性，这可能会导致未定义的行为。

在开始的for循环中添加检查

if(ilop > 999)
{
   break;
}

C 令牌循环段错误问题

C token loop segfault issue

c

valgrind

segmentation-fault