Question

我正在做一个预实验，在其中应该采用预定义的字符串并打印它们是否全部为大写，小写，有数字或混合字符。但是，我不断遇到分段错误（核心已转储）。我尝试调试，但不知道问题出在哪里。任何帮助表示赞赏！

这是我的主力。

#define DIGITTEST1 "12345abcd67890"
#define DIGITTEST2 "1234567890"
#define LOWERTEST1 "hifromJimRies"
#define LOWERTEST2 "hifromjimries"
#define UPPERTEST1 "JIMRIESWASHERE"
#define UPPERTEST2 "JIMRIESWASHERe"
#define ONEMORETEST "9jimr"

void PrintCategory(char *s);

int main(void)
{
PrintCategory(DIGITTEST1);
PrintCategory(DIGITTEST2);
PrintCategory(LOWERTEST1);
PrintCategory(LOWERTEST2);
PrintCategory(UPPERTEST1);
PrintCategory(UPPERTEST2);
PrintCategory(ONEMORETEST);
}

这是我的stringfunc.c

 #include<stdio.h>
    #include<ctype.h>
    #define DIGITTEST1 "12345abcd67890"
    #define DIGITTEST2 "1234567890"
    #define LOWERTEST1 "hifromJimRies"
    #define LOWERTEST2 "hifromjimries"
    #define UPPERTEST1 "JIMRIESWASHERE"
    #define UPPERTEST2 "JIMRIESWASHERe"
    #define ONEMORETEST "9jimr"

void PrintCategory(char *s)
{
  if (isdigit (DIGITTEST1))
    {
      printf ("%s is all digits\n", DIGITTEST1);
    }
  else
    {
      printf ("%s is a mix of various types of characters\n", DIGITTEST1);
    }

  if (isdigit (DIGITTEST2))
    {
      printf ("%s is all digits\n", DIGITTEST2);
    }
  else
    {
      printf ("%s is a mix of various types of characters\n", DIGITTEST2);
    }
  if (islower (LOWERTEST1))
    {
      printf ("%s is all lower case\n", LOWERTEST1);
    }
  else
    {
      printf ("%s is a mix of various types of characters\n", LOWERTEST1);
    }
  if (islower (LOWERTEST2))
    {
      printf ("%s is all lower case\n", LOWERTEST2);
    }
  else
    {
      printf ("%s is a mix of various types of characters\n", LOWERTEST2);
    }
  if (isupper (UPPERTEST1))
    {
      printf ("%s is all upper casae\n", UPPERTEST1);
    }
  else
    {
      printf ("%s is a mix of various types of characters\n", UPPERTEST1);
    }
  if (isupper (UPPERTEST2))
    {
      printf ("%s is all upper case\n", UPPERTEST2);
    }
  else
    {
      printf ("%s is a mix of various types of characters\n", UPPERTEST2);
    }
  if (islower (ONEMORETEST))
    {
      printf ("%s is all lower case\n", ONEMORETEST);
    }
  else
    {
      printf ("%s is a mix of various types of characters\n", ONEMORETEST);
    }

}

Answer 1

ctype.h中的函数（例如isdigit，islower等）正在处理字符。他们的论点是int类型。但是，您将字符串（类型char *）传递给它。确实可以编译，因为可以将char * 隐式转换为int。但是，在这种情况下，代码不正确并导致未定义的行为（在这种情况下为分段错误）。

编译器会警告您有关此错误。例如，当我编译您的代码时，会收到以下警告：

stringfunc.c: In function ‘PrintCategory’:
stringfunc.c:13:7: warning: cast from pointer to integer of different size [-Wpointer-to-int-cast]
stringfunc.c:22:7: warning: cast from pointer to integer of different size [-Wpointer-to-int-cast]
stringfunc.c:30:7: warning: cast from pointer to integer of different size [-Wpointer-to-int-cast]
stringfunc.c:38:7: warning: cast from pointer to integer of different size [-Wpointer-to-int-cast]
stringfunc.c:46:7: warning: cast from pointer to integer of different size [-Wpointer-to-int-cast]
stringfunc.c:54:7: warning: cast from pointer to integer of different size [-Wpointer-to-int-cast]
stringfunc.c:62:7: warning: cast from pointer to integer of different size [-Wpointer-to-int-cast]

如果使用gcc（其他编译器可能具有类似的选项），我强烈建议使用编译器选项-Wall和-Werror进行编译，以避免此类编程错误。使用-Werror，此代码将无法编译。

Answer 2

将字符数组传递给isdigit函数，如下所示。

Program received signal SIGSEGV, Segmentation fault.
0x00000000004005cf in PrintCategory (s=0x400880 "12345abcd67890") at String.c:13
13    if (isdigit (DIGITTEST1))
Missing separate debuginfos, use: debuginfo-install glibc-2.17-292.el7.x86_64

为什么会出现此细分错误？

2 个答案: