c - memmove 留下垃圾 - C

Question

我编写了以下函数，将给定的完整路径拆分为目录、文件名和扩展名。

#include <stdio.h>
#include <string.h>
#include <stdlib.h>

struct path_info {
    char *directory;
    char *filename;
    char *extension;
};

#ifdef WIN32
const char directory_separator[] = "\\";
#else
const char directory_separator[] = "/";
#endif

struct path_info* splitpath(const char *full_path)
{
    size_t length = strlen(full_path);
    struct path_info *p = (struct path_info*) malloc(sizeof(struct path_info) + length + 3);  /* Extra space for padding and shifting */
    if(p)
    {
        char *path = (char *) &p[1];    /* copy of the path */
        char *end = &path[length + 1];  
        char *extension;
        char *last_separator;

        /* copy the path */
        strcpy(path, full_path);
        *end = '\0';
        p->directory = end;
        p->extension = end;
        p->filename  = path;

        last_separator = strrchr(path, directory_separator[0]);    /* Finding the last directory separator */
        if(last_separator) {
            memmove(last_separator + 1, last_separator, strlen(last_separator));  /* inserting a directory separator where null terminator will be inserted */
            p->directory = path;
            *(++last_separator) = '\0';      /* Truncate the directory path */
            p->filename = ++last_separator;  /* Taking the remaining as file name */
        }

        /* Finding the extension starts from second character. This allows handling filenames 
           starts with '.' like '.emacs'.*/
        extension = strrchr(&p->filename[1], '.');
        if(extension) {

            /* shifting the bytes to preserve the extension */
            memmove(extension + 1, extension, strlen(extension));   /* problem happens here */
            p->extension = extension + 1;

            *extension = '\0';  /* Truncates the file name */
        }
    }
    return p;
}


int main(void)
{
    struct path_info *p = splitpath("C:\\my documents\\some.txt");
    printf("Directory : %s\n", p->directory);
    printf("Filename : %s\n", p->filename);
    printf("Extension : %s\n", p->extension);
    return 0;
}

这对于 GCC 上的给定输入非常有效。但它在 MSVC 上失败，在 extension 变量上留下一些垃圾数据。我对出错的地方添加了评论。我不明白为什么 memmove 在 MSVC 上的行为不同？我在两个地方使用了 memmove ，奇怪的是第一个工作正常。

如有任何帮助，我们将不胜感激。

Answer 1

尝试移动 strlen(extension) + 1 字节，这样不仅可以移动扩展字符，还可以移动尾随的空字符。例如，如果扩展名是“abc”，那么您只需将 3 个字符向前移动一个空格。 “c”字符后面可能有一个空字符，但之后没有空字符，因此当您移动字符时，字符串将变为未终止。