# STUDY 'info gdb' (or web equivalent);  ALSO, use `help' inside gdb
#  There are a huge number of valuable tricks there.
# WARNING:  turn off _all_ optimization for gdb, to avoid confusion
#           gcc -O0 -g myfile.c
#  -gstabs also an option for gcc

#TRICK 1:  Note that TAB completion usually works.  Try <TAB> after
#          partial command when stuck.  Also, the cursor keys,
#	   and a subset of emacs commands work on the command line.

#TRICK 2: <return> means execute the last command.

#TRICK 3: After `list 100', `list foo', etc., `list' means list the
#         the following few lines.
#         `search REGEXP'  lists the next line matching REGEXP
#         `reverse-search REGEXP' looks backwards

#TRICK 4: For segfault:
gdb a.out
(gdb) r
(gdb) where
# and then use list, print, etc. to find out why it segfaulted.

#COMMON COMMANDS:
# run, where, print, ptype, list, break, step, next, finish, until
# where:  show stack; print: expression; ptype: print type;
#  list: current source code, or can specify line number, function, file
#  break: at line number of at function
# step:    step to next line or step _into_ current function
# next:    step to next line or step _over_ current function to next line
# finish:  continues until current program finishes
# until:  similar idea for loops, continues until reaching a line number
#           greater than current line number; can specify line number argument

# Equivalent of adding a conditional print statement, but does not require
#   one to recompile
break main.c:121 if x > 0
commands
  silent
  printf "x is %d]n", x
  c
end

#The convenience variable, $bpnum, is set to the number of the last breakpoint.
#This is convenient for recording and referring back to a breakpoint.
break bar
ignore $bpnum 100
set $barBreak $bpnum
# Now the variable $barBreak has as its value the breakpoint number for bar.

#QUESTION TO MYSELF:
# How can one set a breakpoint for 15 lines after the beginning of foo?
# For list, one can do:
list foo
list +15
# But shat is the analog of this for break?

#An alternative method, that works before and after a function, foo, is:
define hook-foo
 ...
end

define hookpost-foo
 ...
end

#Execute every time your program stops:
define hook-stop
  ...
end

# hook-echo and hookpost-echo, as well as other gdb built-in commends.

# We want:  break foo if localVariable == 100
# But gdb complains that localVariable is not part of current scope.
# So, we set a temporary tbreak (one-time only), that creates the
#  desired break, and then continues.
tbreak foo
commands
  silent
  b if localVariable == 100
  c
end

# If error occurs after 100 iterations
break foo
ignore XXXX 100

watch x if x == 0

# Other break commands include:  enable, disable, delete, clear
# Show value of foo(x)  at each breakpoint
display foo(x)

# Create new command
define ps
  shell ps -elfww | grep a.out
end

# Force printing in hex
p/x myvariable

# p and ptype exist.  ptype prints the type.  ptype works on variable or on type
#    p *foo, ptype *foo can also be useful.
ptype struct bar
p (*x)->field
p programFunction(x, 17)
# whatis is more compact than ptype
(gdb) whatis v
type = struct complex
(gdb) ptype v
type = struct complex {
    double real;
    double imag;
}

# Variables can also be reset
# This is useful for confirming if you have found the cause of a bug.
# Set breakpoint to stop at bug, correct variable to right value, and then cont
set myVar = 3
set variable myVar = 3

info types complex
info variables REGEXP
info functions REGEXP
# Print all local variables of foo
info scope foo

# Signals that get in the way.
# For example, some O/S's will pass SIGWINCH to your program, and suppose
#   you don't have a signal handler for SIGWINCH
handle SIGWINCH nostop noprint nopass

#C++
# overloaded methods
b Foo::bar
#  should show a menu of choices
#Alternative
b 'Foo::bar::<TAB>

# If using namespace:
b Name::Foo::bar

# If static, global in a specific file
p 'file.c'::x

# Threads
# By default, break sets breakpoint for all threads, but break thread THREADNO
#    exists.
# Note that when you single-step one thread, the O/S may also allow
#    another thread to execute, and even stop the other thread in the
#    middle of a statement.
# Setting below to on allows only current thread to run.  Setting it to step
#    makes it more likely to follow current thread
#    when using step (and maybe when using next)
set scheduler-locking on/off/step

#TUI mode:  Test User Interface
# Type: C-x a
#    to switch back and forth between TUI mode.  TUI mode uses curses
#    to give you full-screen mode
# `man info' has commands, but some to try are:
help layout
help focus
refresh, update, winheight

#Tracepoints
# If the act of using gdb changes your output due to added delays before
#   an instruction is reached, use tracepoint