指向 NULL 的指针
Pointer to NULL
我有这个功能：
int execve(const char* filename, char* const argv[], char* const envp[]);
并且我需要将 envp 参数设置为 NULL，因此在执行函数之前我需要一个指向 edx 寄存器中的 NULL 的指针（更好的说法是，带有 int 0x80 的系统调用）。问题是，我能做吗：
mov eax, 0
mov edx, eax ; edx points to NULL, no to some address that contains NULL
或者需要我做：
push 0
mov edx, esp ; edx points to some address that contains NULL
这取决于操作系统。在Linux中你可以直接使用一个NULL指针。
On Linux, argv and envp can be specified as NULL. In both cases, this
has the same effect as specifying the argument as a pointer to a list
containing a single null pointer. Do not take advantage of this
misfeature! It is nonstandard and nonportable: on most other UNIX
systems doing this will result in an error (EFAULT).
我有这个功能：
int execve(const char* filename, char* const argv[], char* const envp[]);
并且我需要将 envp 参数设置为 NULL，因此在执行函数之前我需要一个指向 edx 寄存器中的 NULL 的指针（更好的说法是，带有 int 0x80 的系统调用）。问题是，我能做吗：
mov eax, 0
mov edx, eax ; edx points to NULL, no to some address that contains NULL
或者需要我做：
push 0
mov edx, esp ; edx points to some address that contains NULL
这取决于操作系统。在Linux中你可以直接使用一个NULL指针。
On Linux, argv and envp can be specified as NULL. In both cases, this has the same effect as specifying the argument as a pointer to a list containing a single null pointer. Do not take advantage of this misfeature! It is nonstandard and nonportable: on most other UNIX systems doing this will result in an error (EFAULT).