sprintf在Keil中令人讨厌的警告

Question

I am trying to use sprintf(); function in Keil. But I have annoying warning. Let me explain my warning with example code part right below. When i debug, i get;

warning: #167-D: argument of type "uint8_t *" is incompatible with parameter of type "char *restrict"

And it warns me on the line about format types.

I know sprintf function is not a good solution but i really wonder why this warning show off?

Thanks

#include "stm32l0xx.h"  // Device header
#include <stdio.h>

void LCD_show(uint32_t  s_value)

{

  uint8_t str[9], i;

  for ( i = 0; i < 9 ; i++) str[i] = 0;

  sprintf( str, "%9ld", s_value );

}

Answer 1

Fixing your warning:

You have two options: either declare str as char , or use type casting:

sprintf((char *) str, "%9ld", s_value);

Optimizing your code:

The only reason you have a loop is to initialize str array with zeroes. Following is the code that does that in a simple, readable manner, without code overhead:

char str[9] = {0};

Fixing your code:

Excerpt from documentation:

A format specifier follows this prototype:
%[flags][width][.precision][length]specifier
...
Width:
Minimum number of characters to be printed. If the value to be printed is shorter than this number, the result is padded with blank spaces. The value is not truncated even if the result is larger.

This means your code eventually will get a buffer overflow and will crash. Use snprintf !

Answer 2

uint8_t and char is not necessarily the same thing. Usually actually it's typedef'd as unsigned char .