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c++cc-preprocessorline-numbersdynamic-compilation

C/C++ line number

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)
Solution

  • 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__);