Recitation 2: Revision Control

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Recitation 2 Revision Control Makefiles

• George Nychis
• Spring 2009

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Quite different from 213

• Project size 1000s of lines vs 100s.
• Project duration 5 weeks vs 1-2 weeks
• Partners vs. solo developer
• Result
• You cant keep the state for 441 projects in
  your head at all times. Its too big!
• Requires one step more care in development.

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Software EngineeringFor Systems Hackers

• Goals and foundations
• 1-5 developers
• Context Systems code, but not too much is
  systems specific
• Very low overhead and up-front cost
• Like to see benefits w/in a single project

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Overview

• Today Intro Revision Control
• Managing your source code wisely
• Makefiles and automation
• Automate the boring stuff!

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Revision Control

• Before you write a line of code
• Use subversion/CVS/etc.
• Provides access to all old versions of your code
• No more cp file.c file.c.2006-01-01-1059am-oh-god
  -please-let-this-work

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What is revision control?

• A repository that stores each version
• You explicitly check out and check in code
  and changes.
• /tmpgt svn checkout https//moo.cmcl.cs.cmu.edu/441
  /svn/Project1Team1

Password for 'gnychis' A Project1Team1/trunk
A Project1Team1/branches A
Project1Team1/tags Checked out revision 1.
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Why do I want it?

• Super-undo Go to arbitrary versions
• rm rf your source tree? No problem!
• Tracking changes /why did this break?
• Concurrent development
• Snapshots
• Turning in the assignment just make a snapshot
  when you want, and well grade that. You can
  keep developing afterwords.
• Useful, e.g., for optimization contest, or for
  making sure you have something working.

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The repository

• Master copy of code is separate from what you
  work on
• You canhave multipleworking copieschecked
  out.(So can your partner)?

Repository
Your working copy
Laptop working copy
Partner working copy
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Check out and commit

• Explicitly synchronize with the repository

Repository
Checkout / Update
Commit
Your working copy
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And you can see what changed

• Revision control lets you note (and then see)
  what you changed
• gt svn log gtcd.cc
• r986 ntolia 2006-08-01 171338 -0400 (Tue,
  01 Aug 2006) 6 lines
• This allows the sp to get rid of chunks early
  before a transfer is complete.
• Useful when a file is requested in-order and the
  file size gt mem cache size
• And makes it easy to go back to other versions
• --------------------------------------------------
  -------------------
• r987 ntolia 2006-08-02 131621 -0400 (Wed,
  02 Aug 2006) 1 line
• After much thought, I am reverting the last
  patch. We will need to revisit the
• issue when we think about DOT on storage-limited
  clients

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Concurrent edits
Ann
Drew
File v1
Both check out file
Edits (drew-1)? Different part of same file
Edits (ann-1)?
commit
File v2
Update Successfully merged
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Concurrent edits
Ann
Drew
File v1
Both check out file
Edits (drew-1)? Overlap with ann-1
Edits (ann-1)?
commit
File v2
Update (CONFLICT)?
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Resolving Conflicts

• Subversion will give you 3 files
• The original with conflict markers
• The version you were editing
• The latest version in the repository
• You can
• Keep your changes, discarding others
• Toss your changes
• Manually resolve

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Branches

• Multiple paths of development, e.g.
• Release 1.0 only gets security patches
• Development branch gets everything
• tags or snapshots
• Save a good known state. E.g., for handing in.
• You will use tags for checkpoints and final
  version!

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Brief walkthrough (CP1)?
svn co https//moo.cmcl.cs.cmu.edu/441/svn/Proje
ct1Team63 A Project1Team63/trunk A
Project1Team63/branches A Project1Team63/tags C
hecked out revision 1. cd Project1Team63/trunk/
echo -e "include ltstdio.hgt\n\n int main()
return 1 " gt sircd.c svn add sircd.c vim
Makefile svn add Makefile svn ci -m 'adding
Makefile and sircd.c!' cd ../ svn cp trunk
tags/checkpoint1 svn ci -m 'making a tag of the
trunk for checkpoint1!'
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Thoughts on Revision Control

• Update, make, test, then commit
• Update out of habit before you start editing
• Merge often
• Commit format changes separately
• Check svn diff before committing
• Try not to break the checked in copy
• Invasive changes? Maybe a branch
• Dont use svn lock
• Avoid conflicts by good decomposition
  (modularity) and out-of-band coordination

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Rest of the Recitation

• Saving you time
• Learn how to use Makefiles

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Simple gcc
If we have files prog.c The main program
file lib.c Library .c file lib.h Library
header file gcc -c prog.c -o prog.o gcc -c
lib.c -o lib.o gcc lib.o prog.o -o binary
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gcc flags

• Useful flags
• -g debugging hook
• -Wall all warning
• -Werror treat warning as errors
• -O2, -O3 optimization
• -DDEBUG macro for DEBUG (define DEBUG)?

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Examples

• gcc -g -Wall -Werror -c prog.c -o prog.o
• gcc -g -Wall -Werror -c lib.c -o lib.o
• gcc -g -Wall -Werror lib.o prog.o -o binary
• But Dont Repeat Yourself!

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Makefile

• gcc -g -Wall -Werror -c prog.c -o prog.o
• gcc -g -Wall -Werror -c lib.c -o lib.o
• gcc -g -Wall -Werror lib.o prog.o -o binary
• CC gcc
• CFLAGS -g -Wall -Werror
• OUTPUT binary

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Makefile
target dependency1 dependency2 ... unix
command (start line with TAB)? unix
command ... gcc lib.o prog.o -o
binary binary lib.o prog.o gcc lib.o prog.o
-o binary
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binary lib.o prog.o gcc -g -Wall lib.o
prog.o -o binary lib.o lib.c gcc -g -Wall -c
lib.c -o lib.o prog.o prog.c gcc -g -Wall -c
prog.c -o prog.o clean rm .o binary
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binary lib.o prog.o gcc -g -Wall lib.o
prog.o -o binary lib.o lib.c gcc -g -Wall -c
lib.c -o lib.o prog.o prog.c gcc -g -Wall -c
prog.c -o prog.o clean rm .o binary
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CC gcc CFLAGS -g -Wall OUTPUT
binary (OUTPUT) lib.o prog.o (CC)
(CFLAGS) lib.o prog.o -o binary lib.o
lib.c (CC) (CFLAGS) -c lib.c -o
lib.o prog.o prog.c (CC) (CFLAGS) -c
prog.c -o prog.o clean rm .o (OUTPUT)?
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CC gcc CFLAGS -g -Wall OUTPUT
binary (OUTPUT) lib.o prog.o (CC)
(CFLAGS) lib.o prog.o -o binary lib.o
lib.c (CC) (CFLAGS) -c lib.c -o
lib.o prog.o prog.c (CC) (CFLAGS) -c
prog.c -o prog.o clean rm .o (OUTPUT)?
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CC gcc CFLAGS -g -Wall OUTPUT
binary OBJFILES lib.o prog.o (OUTPUT)
(OBJFILES)? (CC) (CFLAGS) (OBJFILES) -o
binary lib.o lib.c (CC) (CFLAGS) -c lib.c
-o lib.o prog.o prog.c (CC) (CFLAGS) -c
prog.c -o prog.o clean rm .o (OUTPUT)?
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CC gcc CFLAGS -g -Wall OUTPUT
binary OBJFILES lib.o prog.o (OUTPUT)
(OBJFILES)? (CC) (CFLAGS) (OBJFILES) -o
binary lib.o lib.c (CC) (CFLAGS) -c lib.c
-o lib.o prog.o prog.c (CC) (CFLAGS) -c
prog.c -o prog.o clean rm .o (OUTPUT)?
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CC gcc CFLAGS -g -Wall OUTPUT
binary OBJFILES lib.o prog.o (OUTPUT)
(OBJFILES)? (CC) (CFLAGS) (OBJFILES) -o
binary .o .c lt dependency (.c)?
_at_ target (.o)? (CC) (CFLAGS) -c lt -o
_at_ clean rm .o (OUTPUT)?
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Simple Test Script

• ./server 6667
• cat testfile.01 ./testscript.py
• cat testfile.02 ./testscript.py
• killall -9 server

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Simple Test Script

• /bin/sh
• echo Starting server on port 6667.
• ./server 6667
• SERVERPID !
• echo Running test files.
• cat testfile.01 ./testscript.py
• cat testfile.02 ./testscript.py
• echo Killing server process.
• kill (SERVERPID)?

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CC gcc CFLAGS -g -Wall OUTPUT
binary OBJFILES lib.o prog.o all
(OUTPUT)? (OUTPUT) (OBJFILES)? (CC)
(CFLAGS) (OBJFILES) -o binary .o .c
lt dependencies (.c)? _at_ target
(.o)? (CC) (CFLAGS) -c lt -o
_at_ clean rm .o (OUTPUT)?
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CC gcc CFLAGS -g -Wall OUTPUT
binary OBJFILES lib.o prog.o all (OUTPUT)
test (OUTPUT) (OBJFILES)? (CC) (CFLAGS)
(OBJFILES) -o binary .o .c lt
dependencies (.c)? _at_ target (.o)? (CC)
(CFLAGS) -c lt -o _at_ test (OUTPUT)? sh
./testscript.sh clean rm .o (OUTPUT)?
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Use Makefile

• make
• make test
• make clean
• Google
• makefile example
• makefile template
• make tutorial

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Useful Unix Commands

• find func_name in files
• grep -r func_name .
• replace bad_func_name to good_func_name
• sed -e s/bad_func_name/good_func_name/g\
• prog.c gt prog.c.new

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Useful Unix Commands

• find a file named prog.c
• find -name prog.c
• download files from Internet
• wget http//address/to/file.tar.gz
• untar and unzip the file
• tar xzvf file.tar.gz

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Project 1

• Checkpoint 2
• Echo server
• Handle multiple clients
• Handle TCP framing
• Q A