enum {
　　OlderSmall = 0，
　　NewerLarge = 1
};
#define Older Newer
#define Small Large
#define _replace_1(Older， Small) Older##Small
#define _replace_2(Older， Small) _replace_1(Older， Small)
void printout( void )
{
　　// _replace_1( Older， Small ) becomes OlderSmall (not NewerLarge)，
　　// despite the #define calls above.
　　printf("Check 1: %d "， _replace_1( Older， Small ) );
　　// The parameters to _replace_2 are substituted before the call
　　// to _replace_1， so we get NewerLarge.
　　printf("Check 2: %d "， _replace_2( Older， Small ) );
}
results is:
Check 1: 0
Check 2: 1


　　----------------------------------------------------------
#define FOO bar
#define QUOTEME_(x) #x
#define QUOTEME(x) QUOTEME_(x)
the code
printf("FOO=%s "， QUOTEME(FOO));
扩展后==>
printf("FOO=%s "， "bar");