GDB-tutorial/gdb.txt

Flags for compiling the code:
------------------------------

-W: Warnings
-Wall: To detect all the warnings. By all warnings means, most
        commonly used warnings.

-Wconversion: To warns use about implicit type conversion.

-Werror: To treat all the warnings as errors.


Some codes in C++ implicitly provides warning even if
we don't mentions warnings flags.

For ex:
    int x{square(i)};

    Here, square function returns a float value. But, curly
    braces initialization gives warning for conversion (implicit-conversion,
    narrowing-conversion).



Printing values to check and debugging:
--------------------------------------

We can use -D flag to do #define a macro from
compile command itself.

For ex:
gcc -DDEBUG <code>.c -o <exe>

Same as doing #define DEBUG 1





GDB (GNU Debugger):
--------------------

Command: gdb --version
    To see the version of gdb.


Command: gdb --silent ./<exe>

    To to print all the info that gdb prints while starting.

Command: gdb --tui

    To run gdb in Text-user interface mode.
    To open TUI when gdb is already On.

    use command: layout src
    
 
We can use these flags with gcc for C code or g++ for C++ code.

Note: To use gdb with compiled code. We need to compile the source 
        code with '-g' flag this will compile the source code and
        generate executable along with Debug symbol which will be used
        by GDB.

        Also, it is not advisable to optimize the code with flags like
        -O3, etc and if the compiler by default optimize the code, we
        can disable it by using -O0. We do this because, optimization
        introduce extra code and make the debugging more complex.

Command: gdb ./<executable>

    To run gdb with given argument as the program to debug.


--------------------------------------------------------------------------------------------------


GDB commands:
-------------

Command: quit or q

    To quit out of current gdb session.


Command: run or r

    To run the executable in gdb.

Command: CTRL + l (key bindings)

    To clear screen in gdb.

Command: refresh

    To clear the screen for gdb.

Command: start

    It will add temporary breakpoint to start
    of the execution i.e. at the main() function
    and stop the execution.

Command: next or n

    To move to next line of code and execute it.
    Next statement and execute it.


Command: step or s

    To move into the function execution instead of
    just executing the function and returning the result.


Command: finish or fin

    To step out of the function.

Command: list or l


    To show some context of the current execution w.r.t
    code


        To show some context of the current execution w.r.t
        code
    
    Also using command "list <line-number>" prints the 
    context w.r.t given line number.

Command: set listsize <size>

    To show more content while using list command


Command: print <variable-name> or p <variable-name>

    To print the current value of the variable name.
    It also de-reference operator to show the content
    as well to print the value present at the address
    in form of structure.

    for ex:

        print l->root

        address with pointer type specified
        
        print *l.root

        print the whole structure of the object.


Command: c or continue

    To continue the execution till next breakpoint
    or termination of program.

Command: whatis <type>

    To specify what is symbol which maybe user-defined
    actually is....

    For ex:

    whatis list_t
    type = struct list


Command: ptype <type>

    It gives more information as compare to whatis.

    For ex:
    ptype list_t
    type = struct list{
        node_t *root;
    }


    Note: Both ptype and whatis can be used with variable as well


Command: info scope <argument>

    To show what is present in the scope of the current function in execution.


Commaond: info types

    To list all the different type of symbols in the program.


Command: tbreak <line-number>

    To give temporary breakpoint to the program.
    This breakpoint will stop the program execution only once.

Command: info breakpoints

    To show some information about breakpoints.

Command: break <line-number>

    These are permanent breakpoint

Command: break <line-number>

    These are permanent breakpoint

    Note: To delete a breakpoint we can use
          command

          Command:
          (gdb)delete <breakpoint-number>

Command: layout src

    To open the TUI with src code.

Command: help layout

    To know more about layout.

Command: layout reg

    To show register info.

Command: layout asm

    To show asm info.

Command: CTRL+x 1,2... (key bindings)

    To cycle through various layout for a single window.

Command: CTRL+x 0 (key bindings)

    To navigate to gdb terminal and TUI window

    If view gets messed up use CTRL+l

    Same thing for navigation can be done 
    using focus cmd and focus src window.

Command: CTRL+p (key bindings)

    will move to previous command if focus is on src window.


Command: winheight src -2

    To change the size of window passed as an argument. In
    this case, decrease by 2.