Embedded projects use the C language structure segment feature to assert the validity of macro validation data range

We won't talk much about the features of bit segments, but read the corresponding C language books for more information.

Today we introduce assertion macros. What is an assertion macro? An assertion macro can be thought of as an implementation of a macro that verifies the validity of a data range. Let's look at the code:

#include <stdio.h>
// Structural body segment 
#define   CHECK(x)      sizeof(struct {unsigned:(-!!(x));})
// Check that the constants are in 1 If not, compile error 
// Such as the definition 1 a 0 to 1000 If passed in xxx Less than 0 Or greater than 1000 , the compiler detects an error 
#define   DEFI(a , xxx)   a = CHECK(xxx<0) + CHECK(xxx>1000) + xxx 
int main(void)
{
 int a ;
 DEFI(a , 2000) ; 
 printf("a:%d \n" , a);
 return 0 ; 
}

Operation results:

Compile error because the range of 2000 is not 0~1000:

If we change it to a valid data range, say 1000, let's look at the results:

#include <stdio.h>
// Structural body segment 
#define   CHECK(x)      sizeof(struct {unsigned:(-!!(x));})
// Check that the constants are in 1 If not, compile error 
// Such as the definition 1 a 0 to 1000 If passed in xxx Less than 0 Or greater than 1000 , the compiler will find an error 
#define   DEFI(a , xxx)   a = CHECK(xxx<0) + CHECK(xxx>1000) + xxx 
int main(void)
{
 int a ;
 DEFI(a , 1000) ; 
 printf("a:%d \n" , a);
 return 0 ; 
}

This approach can be used in the development of embedded projects, remind yourself to always pay attention to the range of data types, I think this is a very good programming aid check.

conclusion