[英]Why my macro doesn't compile?
#define LINE_FILE ("Line"#__LINE__"of file"__FILE__)
int main(void)
{
printf("%s", LINE_FILE);
}
我的期望:
LINE_FILE =“文件名的行號線”
和printf()
可以輸出此字符串。
http://ww2.sinaimg.cn/large/005FchG6gw1esb0pvwxr3j30he06jjt7.jpg
__LINE__
不會擴展為“字符串”,而是擴展為int
。
為了解決這個問題,您可能需要執行以下操作:
#define _LINE_FILE2(filename, linenumber) "Line " #linenumber " of " filename
#define _LINE_FILE1(filename, linenumber) _LINE_FILE2(filename, linenumber)
#define LINE_FILE _LINE_FILE1(__FILE__, __LINE__)
有關(gcc)的更多詳細信息
您需要一個字符串化助手
#define STR_HELPER(x) #x
#define STR(x) STR_HELPER(x)
然后
#define LINE_FILE ("Line" STR(__LINE__)"of file"__FILE__)
AFAIK您不能在預處理器上執行此操作,通常的方法是:
printf("Line %d of file %s", __LINE__, __FILE__);
要調試宏,可以單獨使用C預處理器。
行號
#define LINE_FILE_WRONG ("Line"#__LINE__"of file"__FILE__)
// solution of LPs
#define STR_HELPER(x) #x
#define STR(x) STR_HELPER(x)
#define LINE_FILE ("Line " STR(__LINE__) " of file " __FILE__)
LINE_FILE_WRONG
LINE_FILE
為此文件運行C預處理程序並獲取
% cpp linenumber.c
# 1 "linenumber.c"
# 1 "<built-in>"
# 1 "<command-line>"
# 1 "/usr/include/stdc-predef.h" 1 3 4
# 1 "<command-line>" 2
# 1 "linenumber.c"
("Line"#8"of file""linenumber.c")
("Line " "9" " of file " "linenumber.c")
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