c - 在 C 中删除内联注释时的意外行为

Question

堆栈溢出!我正在学习C技术。我有一个获取输入文件、查找文件并将内容写入输出文件而不带注释的函数。该功能有效，但在某些情况下也会刹车。我的功能:

    void removeComments(char* input, char* output)
{
    FILE* in = fopen(input,"r");
    FILE* out = fopen(ouput,"w");
    char c;
    while((c = fgetc(in)) != EOF)
    {
       if(c == '/')
       {

          c = fgetc(in);
          if(c == '/')
          {
           while((c = fgetc(in)) != '\n');
          }
          else
          {
            fputc('/', out);
          }
       }
       else
       {
           fputc(c,out);
       }
    }
    fclose(in);
    fclose(out);
}

但是当我将这样的文件作为输入时:

// Parameters: a, the first integer; b the second integer.
// Returns: the sum.
int add(int a, int b) 
{
    return a + b; // An inline comment.
}
int sample = sample;

当删除内联注释时，由于某种原因它无法到达 '\n' 并给出输出:

int add(int a, int b) 
{
    return a + b; }
int sample = sample;

[编辑]谢谢你帮助我!它适用于我发布的案例，但它在另一个案例中刹车。当前代码:

FILE* in = fopen(input,"r");
FILE* out = fopen(output,"w");

if (in == NULL) {
  printf("cannot read %s\n", input);
  return; /* change signature to return 0 ? */
}
if (out == NULL) {
  printf("cannot write in %s\n", output);
  return; /* change signature to return 0 ? */
}

int c;
int startline = 1;

while((c = fgetc(in)) != EOF)
{
   if(c == '/')
   {
      c = fgetc(in);

      if(c == '/')
      {
        while((c = fgetc(in)) != '\n')
        {
          if (c == EOF) {
            fclose(in);
            fclose(out);
            return; /* change signature to return 1 ? */
          }
        }
        if (! startline)
          fputc('\n', out);
        startline = 1;
      }
      else if (c == EOF)
        break;
      else {
        fputc('/', out);
        startline = 0;
      }
   }
   else
   {
     fputc(c,out);
     startline = (c == '\n');
   }
}

fclose(in);
fclose(out);

当文件包含除法时，第二个变量消失。示例:

int divide(int a, int b) 
    {
        return a/b; 
    }

它回馈:

int divide(int a, int b) 
    {
        return a/; 
    }

Answer 1

之后

while((c = fgetc(in)) != '\n');

你需要一个fputc('\n', out);

补充说明:

在

char c;
while((c = fgetc(in)) != EOF)

c 必须是 int 才能管理 EOF

只是一个错字:ouput 必须是output 才能编译

在你读到一个 '/' 之后，你没有很好地管理 EOF

您错过了检查fopen的结果

---

一个建议:

#include <stdio.h>

void removeComments(char* input, char* output)
{
    FILE* in = fopen(input,"r");
    FILE* out = fopen(output,"w");

    if (in == NULL) {
      printf("cannot read %s\n", input);
      return; /* change signature to return 0 ? */
    }
    if (out == NULL) {
      printf("cannot write in %s\n", output);
      return; /* change signature to return 0 ? */
    }

    int c;

    while((c = fgetc(in)) != EOF)
    {
       if(c == '/')
       {
          c = fgetc(in);

          if(c == '/')
          {
            while((c = fgetc(in)) != '\n')
            {
              if (c == EOF) {
                fclose(in);
                fclose(out);
                return; /* change signature to return 1 ? */
              }
            }
            fputc('\n', out);
          }
          else if (c == EOF) {
            fputc('/', out);
            break;
          }
          else
            fputc('/', out);
            fputc(c, out);
       }
       else
       {
         fputc(c,out);
       }
    }

    fclose(in);
    fclose(out);
     /* change signature to return 1 ? */
}

int main(int argc, char ** argv)
{
  removeComments(argv[1], argv[2]);
}

---

正如 Tormund Giantsbane 在评论中所说，最好完全删除仅包含评论的行(评论从第一列开始)，新提案就是这样做的:

#include <stdio.h>

void removeComments(char* input, char* output)
{
    FILE* in = fopen(input,"r");
    FILE* out = fopen(output,"w");

    if (in == NULL) {
      printf("cannot read %s\n", input);
      return; /* change signature to return 0 ? */
    }
    if (out == NULL) {
      printf("cannot write in %s\n", output);
      return; /* change signature to return 0 ? */
    }

    int c;
    int startline = 1;

    while((c = fgetc(in)) != EOF)
    {
       if(c == '/')
       {
          c = fgetc(in);

          if(c == '/')
          {
            while((c = fgetc(in)) != '\n')
            {
              if (c == EOF) {
                fclose(in);
                fclose(out);
                return; /* change signature to return 1 ? */
              }
            }
            if (! startline)
              fputc('\n', out);
            startline = 1;
          }
          else if (c == EOF) {
            fputc('/', out);
            break;
          }
          else {
            fputc('/', out);
            fputc(c, out);
            startline = 0;
          }
       }
       else
       {
         fputc(c,out);
         startline = (c == '\n');
       }
    }

    fclose(in);
    fclose(out);
     /* change signature to return 1 ? */
}

int main(int argc, char ** argv)
{
  removeComments(argv[1], argv[2]);
}

编译和执行:

pi@raspberrypi:/tmp $ gcc -pedantic -Wextra -g r.c
pi@raspberrypi:/tmp $ cat i
// Parameters: a, the first integer; b the second integer.
// Returns: the sum.
int add(int a, int b) 
{
    return a + b/c; // An inline comment.
}
int sample = sample;
pi@raspberrypi:/tmp $ ./a.out i o
pi@raspberrypi:/tmp $ cat o
int add(int a, int b) 
{
    return a + b/c; 
}
int sample = sample;

---

正如 DavidC 所说。在注释中，如果//放在字符串中，结果将不是预期的结果，字符甚至非法也是这种情况(我的意思是 '//' 不能更改)，C 注释(/* ..//... */) 等