C99转ANSI注释程序文件输入异常，终端输入正常问题排查

我写了一个程序，用来将输入文本中的C99风格注释转换为等价的ANSI C注释。该程序在在线终端、通过终端手动输入文本时运行正常，但通过文件输入文本时出现异常。调试发现，初始化值为0的incomment变量在文件输入的第一次循环时变为1，导致程序逻辑出错。我尝试过将incomment初始化为-1并在首次循环重置，也更换过PowerShell、Bash等终端，但问题仍存在。

预期调用#1 #

// My useful program
#include <stdio.h>
int main() { /* Our main function */
    printf("Hello world!\n"); // print hello
    // done, phew!
    return 0;
}

预期输出 #

/* My useful program */
#include <stdio.h>
int main() { /* Our main function */
    printf("Hello world!\n"); /* print hello */
    /* done, phew! */
    return 0;
}

预期调用#2 #

//// ***** this code is bad, comment it out *****
// printf("Hello world\n"); /* prints hello world */
// return 0;
// /* done, phew! */

预期输出2 #

/*// ***** this code is bad, comment it out ***** */
/* printf("Hello world\n");  prints hello world  */
/* return 0; */
/*  done, phew!  */

程序代码 #

#include <stdio.h>
#define STAR 42
#define FWDSLASH 47
int main(int argc, char *argv[]) {
    int ch, incomment = 0, slashlast = 0, starlast = 0;
    
    while ((ch = getchar()) != EOF) {

    // check if line is in comment
        
        if (incomment)
        {   
            
            // Ignore any other /* combinations
            if (ch == '/')
            {
                if (starlast) {
                    starlast = 0;
                    continue;
                }
                if (slashlast)
                {
                    printf("/");
                }
                slashlast = 1;

            }
            // if newline found, set end */
            else {
                
                if (ch == '*')
                {
                    
                    if (slashlast) {
                        slashlast = 0;
                        continue;
                    }
                    if (starlast)
                    {
                        printf("*");
                    }
                    starlast = 1;
                }
                else
                {
                    
                    if (ch == '\n')
                    {
                        if (starlast)
                        {
                            printf("*");
                            starlast = 0;
                            
                        }
                        else if (slashlast)
                        {
                            printf("/");
                            slashlast = 0;
                            
                        }
                        incomment = 0;
                        printf(" */");
                        putchar(ch);
                        
                    }
                    else
                    {
                        if (starlast)
                        {
                            printf("*");
                            putchar(ch);
                        }
                        else if (slashlast)
                        {
                            printf("/");
                            putchar(ch);
                        }
                        else
                        {
                            putchar(ch);
                        }
                        starlast = 0;
                        slashlast = 0;
                    }
                }
                
                
            }    
        }
        else
        {
            // Not in comment
            
            //Check for // combination and replace with /* combination
            if (ch == FWDSLASH)
            {
                //Two slashes foud
                if (slashlast)
                {
                    incomment = 1;
                    printf("/*");
                    // Done checking for slashes
                    slashlast = 0;
                }
                else
                {
                    slashlast = 1;
                }
                
                
            }   
            else
            {
                if (slashlast)
                {
                    // Print the previous slash then print self.
                    printf("/");
                    putchar(ch);
                    slashlast = 0;
                }
                else
                {
                    putchar(ch);
                    slashlast = 0;
                }
                
            }

        }

    }
    

    return 0;

}

内容的提问来源于stack exchange，提问作者NovaT