#line

Introduction

The #line directive allows you to define arbitrary line numbers for the source lines. Normally, the compiler counts lines starting at line number 1; using the #line directive, you can specify an arbitrary line number at any point. The compiler then uses that line number for subsequent counts.

Program

#include  main() {     printf("A\n");          //A       #line100               //H     printf("B\n");          //B     printf("C FILE %s LINE %d\n", __FILE__, __LINE__ );//C      #line200               //K      printf("D\n");          //D     printf("E\n");          //E } 

Explanation

1. The statement H indicates the #line directive.

2. The #line number in statement B is taken as 100 and for statement C, it is taken as 101.

3. The #line number in statement D is taken as 200 and for statement E, it is taken as 201.

4. If you introduce any error in statement B then the compiler will display the error at #line number 100.

5. C has provided two special identifiers: __FILE__ and __LINE__, which indicate the file name of the source file and the current line number, respectively.

Point to Remember

#line is used to indicate line numbers which can be used for debugging.