NAME

aebisect - search for a delta which changed project behaviour

SYNOPSIS

aebisect [option...] [-Branch branch1] -DELta delta1 [-Branch branch2] -DELta delta2 -- command [command_args]

DESCRIPTION

The aebisect command is used to determine when in a project history some property or behavior changed. It does this by means of a bisection search through the inventory of deltas. The user must specify starting and ending deltas, which may be in historical branches of the project.

For each delta tested in the search, aebisect sets up a development directory, builds the project, and then runs the specified command in the development directory. By iteration, aebisect finds two consecutive deltas where the return code of command changed.

Note: aebisect can take considerable CPU effort, since it (normally) does a full build from scratch for each delta tested.

OPTIONS

The following options are understood:

-Help

Show usage information.

-Project project-name

specify the project (otherwise done via the AEGIS_PROJECT environment variable)

-Change change-number

specify the change to use for the processing (otherwise done via the AEGIS_CHANGE environment variable). The change must be in the awaiting_development state; this ensures a correct environment for building and testing.

-Branch branch-extension

specify the branch for one of the deltas. Defaults to the baseline branch of the project. Use -b - (single dash) to specify the trunk. Branch specifiers must precede the corresponding delta specifiers.

-Logfile logfile

specify where normal output goes; defaults to $HOME/aebisect.log.

-Verbose

produce more diagnostic information (both logfile and standard output).

-Keep

do not delete working files, which are in a temporary directory. Warning: these may be voluminous!

-DIRectory path

specify a development directory to use for building and testing.

-Minimum

use the -minimum option for the builds.

-Nobuild

skip the build steps. This option is useful if the test command only involves source files. (Consider using aeannotate(1) instead.)

-Zero_only

treat all test result codes other than 0 as equivalent.

DIAGNOSTICS

Normally, exit status is 0 if consecutive deltas are found to bracket a change in the test command result. Exit status is 1 if errors are detected in arguments. Exit status is 2 if a subordinate command fails (possibly leaving the development directory in an uncertain state) or if the test behavior is found to be inconsistent with bisection search.

SIGNALS

aebisect will stop on INT, QUIT, and TERM signals, probably leaving the development directory in an uncertain state.

EXAMPLE

Suppose a bug was introduced by development on project foo-4.5, sometime between version 1.2.D003 and 4.5.D006, and you have written an Aegis test script for the bug (see aent(1)), called /wrk/test/00/t0007a.sh, taking an argument for system architecture. Then the following should isolate the change which introduced the bug:

 % aenc -p foo-4.5 -c 20 -file caf
 % aebisect -p foo-4.5 -c 20 -b 1.2 -del 3 -b 4.5 -del 6 \
     -- sh /wrk/test/00/t0007a.sh linux-i486

Note that the full path for the test script is specified, since the command is executed in a development directory.

BUGS

aebisect depends on aecp -delta for historical reconstructions. This can be problematic.

It is possible for a build to fail: derived files from the baseline may poison the build, or there may have been changes in the system infrastructure since the old deltas were integrated. In such cases, aebisect exits. The user may then snoop around the development directory, fix something, rebuild, perform the test, and use the logfile to see how to proceed. Remember to aedbu when done.

In some situations the problem may be cured by an additional step between aedb and aeb. A command to be interposed may be defined via the environment variable AEBISECT_DB_HOOK; this command is executed after aecp, so it may be used to patch source files — see the script source for details.

COPYRIGHT

This is free software; see the source for copying conditions. There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.