GDB Debug Print prints out variable values or is inaccurate

The compile option is added to-O, even if it is-o0, it does not display properly, need to add-gstabs+ this compile option,
-gdwarf-2 This compilation option will conflict with-gstabs+, remove-gstabs+, only the-gdwarf-2 option can solve GDB debugging when the print variable is not allowed and some variables are not displayed.

Reference http://bbs.csdn.net/topics/390708777?page=1#post-398696875

In addition, compile the time add-wall, debug the program before, into GDB, input list will show the main () function before and after 10 lines of code, if just
-W, in the same scenario, the list does not list code. (Accidental discovery)

GDB Debug Print prints out variable values or is inaccurate