Meanwhile, Harry has been coding as well. He heard somebody say that it’s best to compile with all the warnings turned on, so he decides to give it a try.
lottery harry$ gcc -std=c99 -Wall -Wextra -Werror lottery.c cc1: warnings being treated as errors lottery.c:5: warning: unused parameter 'white_balls' lottery.c:5: warning: unused parameter 'power_ball'
I say! The code has some warnings. The calculate_result() function
isn’t using its parameters. Harry looks at the situation and realises the
problem immediately: That function should be checking its arguments for
validity! The power ball can be from 1 to 39 inclusive. The white balls can be
1 to 59 inclusive. So he implements the error checking.
int calculate_result(int white_balls[5], int power_ball)
{
for (int i=0; i<5; i++)
{
if (
(white_balls[i] < 1)
|| (white_balls[i] > 59)
)
{
return -1;
}
}
if (
(power_ball < 1)
|| (power_ball > 39)
)
{
return -1;
}
return 0;
}
Grand. Let’s see if it compiles.
lottery harry$ gcc -std=c99 -Wall -Wextra -Werror lottery.c lottery harry$ ls -l total 32 -rwxr-xr-x 1 harry staff 8904 May 31 10:22 a.out -rw-r--r-- 1 harry staff 843 May 31 10:22 lottery.c
Quite. But Harry decides to diff before committing, just for good measure.
lottery harry$ vv diff === ================ === Modified: File @/lottery.c --- @/lottery.c 76a16c36b9a4cea4a222ff8132f9f242fa04bed1 +++ @/lottery.c 2011/05/31 15:22:18.000 +0000 @@ -4,6 +4,25 @@ int calculate_result(int white_balls[5], int power_ball) { + for (int i=0; i<5; i++) + { + if ( + (white_balls[i] < 1) + || (white_balls[i] > 59) + ) + { + return -1; + } + } + + if ( + (power_ball < 1) + || (power_ball > 39) + ) + { + return -1; + } + return 0; }
Good show. Time to commit the change.
lottery harry$ vv commit -m "fix some warnings" revision: 3:7290fd8b3372dfecf5622dec12284d602553258e branch: master who: harry when: 2011/05/31 10:23:07.968 -0500 comment: fix some warnings parent: 2:8d1b667537d569b307e320004ca7cfb10d8aea64
No problems there. This time he remembers that he needs to push his changes to the server.
But Sally has been working at the same time and she had her change ready to commit and push first.
lottery sally$ vv commit -m "change order of the command line args to be \ more like what the user will expect" revision: 3:7414ae0aa096674df94e6f3e142e893709ff3ac6 branch: master who: sally when: 2011/05/31 10:23:57.285 -0500 comment: change order of the command line args to be more like what the user will expect parent: 2:8d1b667537d569b307e320004ca7cfb10d8aea64 lottery sally$ vv push Pushing to http://server.futilisoft.com:8080/repos/lottery: Pushing... Done.
So Harry tries to push his changes.
lottery harry$ vv push vv: Error 234 (sglib): The branch needs to be merged.
What’s all this then? Veracity is not allowing Harry to push his change because it would result in the master branch having two heads.
Harry uses pull to bring in changes.
lottery harry$ vv pull Pulling from http://server.futilisoft.com:8080/repos/lottery: Pulling... Done. lottery harry$ vv heads revision: 3:7290fd8b3372dfecf5622dec12284d602553258e branch: master who: harry when: 2011/05/31 10:23:07.968 -0500 comment: fix some warnings parent: 2:8d1b667537d569b307e320004ca7cfb10d8aea64 revision: 4:7414ae0aa096674df94e6f3e142e893709ff3ac6 branch: master who: sally when: 2011/05/31 10:23:57.285 -0500 comment: change order of the command line args to be more like what the user will expect parent: 2:8d1b667537d569b307e320004ca7cfb10d8aea64 lottery harry$ vv branch list master (needs merge)
Harry can see from the output of vv heads that the master branch is now ambiguous and needs to be merged.
lottery harry$ vv merge 1 updated, 0 deleted, 0 added, 1 merged, 0 unresolved
Splendid. Now the merge is in the working copy.
lottery harry$ vv status Modified: @/lottery.c Found: @/a.out
Everything seems to be ship-shape and Bristol fashion. Harry wants to see what happened.
lottery harry$ vv diff === ================ === Modified: File @/lottery.c --- @/lottery.c 603c9fe57661de7967b3926feb3cf29438dfcbda +++ @/lottery.c 2011/05/31 15:24:47.000 +0000 @@ -30,16 +30,16 @@ { if (argc != 7) { - fprintf(stderr, "Usage: %s power_ball (5 white balls)\n", argv[0]); + fprintf(stderr, "Usage: %s (5 white balls) power_ball\n", argv[0]); return -1; } - int power_ball = atoi(argv[1]); + int power_ball = atoi(argv[6]); int white_balls[5]; for (int i=0; i<5; i++) { - white_balls[i] = atoi(argv[2+i]); + white_balls[i] = atoi(argv[1+i]); } int result = calculate_result(white_balls, power_ball);
Interesting. Diff shows Sally’s changes. This is because the diff was performed against changeset 7290fd8b3372dfecf5622dec12284d602553258e. Harry types vv parents to see the version of the tree on which his current pending changeset is based.
lottery harry$ vv parents revision: 3:7290fd8b3372dfecf5622dec12284d602553258e branch: master who: harry when: 2011/05/31 10:23:07.968 -0500 comment: fix some warnings parent: 2:8d1b667537d569b307e320004ca7cfb10d8aea64 revision: 4:7414ae0aa096674df94e6f3e142e893709ff3ac6 branch: master who: sally when: 2011/05/31 10:23:57.285 -0500 comment: change order of the command line args to be more like what the user will expect parent: 2:8d1b667537d569b307e320004ca7cfb10d8aea64
Because it is a merge, his working copy has two parents. The resulting DAG node will have two parents as well.
His code is already committed. Apparently Veracity was able to merge Sally’s changes directly into Harry’s modified copy of the file without any conflicts. Smashing! Let’s see if it compiles.
lottery harry$ gcc -std=c99 -Wall -Wextra -Werror lottery.c lottery harry$ ls -l total 32 -rwxr-xr-x 1 harry staff 8904 May 31 10:25 a.out -rw-r--r-- 1 harry staff 843 May 31 10:24 lottery.c
Very well then. So Harry is ready to commit the merge.
lottery harry$ vv commit -m "merge" revision: 5:ee2493eac8e7fc751e2b57a87a3768a192770ae3 branch: master who: harry when: 2011/05/31 10:25:47.532 -0500 comment: merge parent: 3:7290fd8b3372dfecf5622dec12284d602553258e parent: 4:7414ae0aa096674df94e6f3e142e893709ff3ac6
And now vv parents shows only one node but that node has two parents.
lottery harry$ vv parents Parents of pending changes in working copy: revision: 5:ee2493eac8e7fc751e2b57a87a3768a192770ae3 branch: master who: harry when: 2011/05/31 10:25:47.532 -0500 comment: merge parent: 3:7290fd8b3372dfecf5622dec12284d602553258e parent: 4:7414ae0aa096674df94e6f3e142e893709ff3ac6
And push.
lottery harry$ vv push Pushing to http://server.futilisoft.com:8080/repos/lottery: Pushing... Done.