C/C++ line number

Question

In the sake of debugging purposes, can I get the line number in C/C++ compilers? (standard way or specific ways for certain compilers)

e.g

if(!Logical)
    printf("Not logical value at line number %d \n",LineNumber);
    // How to get LineNumber without writing it by my hand?(dynamic compilation)

Answer 1

You should use the preprocessor macro __LINE__ and __FILE__. They are predefined macros and part of the C/C++ standard. During preprocessing, they are replaced respectively by a constant string holding an integer representing the current line number and by the current file name.

Others preprocessor variables :

• __func__ : function name (this is part of C99, not all C++ compilers support it)
• __DATE__ : a string of form "Mmm dd yyyy"
• __TIME__ : a string of form "hh:mm:ss"

---

Your code will be :

if(!Logical)
  printf("Not logical value at line number %d in file %s\n", __LINE__, __FILE__);