__FILE__与__LINE__宏

看<<C intefaces and implementations>>时看到__FILE__与__LINE__，不甚理解,于是乎查了下。

__FILE__与__LINE__是预定义的宏，实现了标准的编译器中均可使用这些宏

__FILE__宏输出的是当前输入文件的路径，含文件名，而__LINE__宏输出当前代码所在的行号（整数变量)

以下文字部分引用自http://gcc.gnu.org/onlinedocs/cpp/Standard-Predefined-Macros.html

__FILE__

This macro expands to the name of the current input file, in the form of a C string constant. This is the path by which the preprocessor opened the file, not the short name specified in ` #include' or as the input file name argument. For example,  "/usr/local/include/myheader.h" is a possible expansion of this macro. 

__LINE__

This macro expands to the current input line number, in the form of a decimal integer constant. While we call it a predefined macro, it's a pretty strange macro, since its “definition” changes with each new line of source code.

__FILE__ and __LINE__ are useful in generating an error message to report an inconsistency detected by the program; the message can state the source line at which the inconsistency was detected. For example,

     fprintf (stderr, "Internal error: "
                      "negative string length "
                      "%d at %s, line %d.",
              length, __FILE__, __LINE__);

#include<stdio.h>
int main(){
	printf("%s\n",__FILE__);
	printf("%d\n",__LINE__);

	return 0;
}