[转载]用__attribute__((deprecated))管理过时的代码

定义：http://www.keil.com/support/man/docs/armcc/armcc_chr1359124981701.htm

attribute((deprecated)) variable attribute

The deprecated variable attribute enables the declaration of a deprecated variable without any warnings or errors being issued by the compiler. However, any access to a deprecated variable creates a warning but still compiles.

The warning gives the location where the variable is used and the location where it is defined. This helps you to determine why a particular definition is deprecated.

Note

This variable attribute is a GNU compiler extension that the ARM compiler supports.

Example

extern int Variable_Attributes_deprecated_0 __attribute__((deprecated));
extern int Variable_Attributes_deprecated_1 __attribute__((deprecated));
void Variable_Attributes_deprecated_2()
{
    Variable_Attributes_deprecated_0=1;
    Variable_Attributes_deprecated_1=2;
}

Compiling this example generates two warning messages.

以下转自：https://blog.csdn.net/benkaoya/article/details/52368638

在开发一些库的时候，API的接口可能会过时，为了提醒开发者这个函数已经过时。可以在函数声明时加上attribute((deprecated))属性，如此，只要函数被使用，在编译是都会产生警告，警告信息中包含过时接口的名称及代码中的引用位置。

attribute可以设置函数属性（Function Attribute）、变量属性（Variable Attribute）和类型属性（Type Attribute）。
attribute语法格式为：attribute ((attribute))
注意：使用attribute的时候，只能函数的声明处使用attribute，

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

#ifdef __GNUC__
#    define GCC_VERSION_AT_LEAST(x,y) (__GNUC__ > (x) || __GNUC__ == (x) && __GNUC_MINOR__ >= (y))
#else
#    define GCC_VERSION_AT_LEAST(x,y) 0
#endif

#if GCC_VERSION_AT_LEAST(3,1)
#    define attribute_deprecated __attribute__((deprecated))
#elif defined(_MSC_VER)
#    define attribute_deprecated __declspec(deprecated)
#else
#    define attribute_deprecated
#endif


/* Variable Attribute */
attribute_deprecated int  variable_old = 0;

/* Function Attribute */
attribute_deprecated void function_old(void);

void function_old(void)
{
    printf("old function.\n");
    return;
}

int main(void)
{
    variable_old++;

    function_old();

    return EXIT_SUCCESS;
}

在编译时会出现类似警告：

# gcc attribute_deprecated.c -o test
attribute_deprecated.c: In function ‘main’:
attribute_deprecated.c:33: warning: ‘variable_old’ is deprecated (declared at attribute_deprecated.c:20)
attribute_deprecated.c:35: warning: ‘function_old’ is deprecated (declared at attribute_deprecated.c:25)