[英]pointer in C function needs unsigned type array, but my array is signed
I have a function as follows that processes the information contained in an array of type unsigned char:我有一个函数,它处理包含在 unsigned char 类型数组中的信息:
unsigned char LRCsimple(unsigned char *p, createLRC , unsigned char length)
{
}
Works great for mostly unsigned char arrays.适用于大多数无符号字符数组。
Now, I have a signed array and when I use such a function and it works very well, but I have a warning when compiling the code:现在,我有一个带符号的数组,当我使用这样的函数时,它工作得很好,但是在编译代码时出现警告:
> ../src/apptcpipserver.c:102:9: warning: pointer targets in passing argument 1 of 'LRCsimple' differ in signedness [-Wpointer-sign]
if (0x01 == LRCsimple(apptcpipserverData.cRxedData,0x00,(apptcpipserverData.cRxedData[0x02] - 0x02)))
If I want to avoid this warning, I think the optimal solution is to create a function similar to the one above, but for a signed array, as follows:如果我想避免这个警告,我认为最佳解决方案是创建一个类似于上面的函数,但对于有符号数组,如下所示:
unsigned char signedLRCsimple(char *p, createLRC , unsigned char length)
{
}
Or is there something else I can do to avoid that warning message?或者我还能做些什么来避免该警告消息?
Strict aliasing rule allows unsigned char
and char
alias.严格的别名规则允许
unsigned char
和char
别名。 Therefore you should be able reuse LRCsimple
for processing char*
.因此,您应该能够重用
LRCsimple
来处理char*
。
Therefore signedLRCsimple
could be implemented as:因此,
signedLRCsimple
可以实现为:
unsigned char signedLRCsimple(char *p, createLRC xxx, unsigned char length)
{
return LRCsimple((unsigned char*)p, xxx, length);
}
To avoid forcing client to change their code to use signedLRCsimple
you could use generic selection introduced in C11 in form of _Generic
.为避免强制客户端更改其代码以使用
signedLRCsimple
您可以使用 C11 中以_Generic
形式引入的泛型选择。 Typically it is used to select a function pointer basing on the type of first argument of _Generic
.通常,它用于根据
_Generic
的第一个参数的类型选择函数指针。
#define LRCsimple(p, xxx, length) \
_Generic((p), unsigned char*: LRCsimple, \
char *: signedLRCsimple)(p, xxx, length)
Whenever LRCsimple
is called the generic selection selects between LRCsimple
for unsigned char*
and signedLRCsimple
for char*
.每当
LRCsimple
被称为之间的通用选择选择LRCsimple
为unsigned char*
和signedLRCsimple
的char*
。 For other types an error is raised.对于其他类型,会引发错误。
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