freebsd-dev/tools/build/options/WITH_META_MODE
Bryan Drewery 63decaa682 WITH_META_MODE: Correct description of missing .meta file.
Sponsored by:	EMC / Isilon Storage Division
2016-05-24 23:15:52 +00:00

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.\" $FreeBSD$
Creates
.Xr make 1
meta files when building, which can provide a reliable incremental build when
using
.Xr filemon 4 .
The meta file is created in the OBJDIR as
.Pa target.meta .
These meta files track the command ran, its output, and the current directory.
When the
.Xr filemon 4
module is loaded, any files used by the commands executed will be tracked as
dependencies for the target in its meta file.
The target will be considered out-of-date and rebuilt if any of the following
are true compared to the last build:
.Bl -bullet -compact
.It
The command to execute changes.
.It
The current working directory changes.
.It
The target's meta file is missing, if it had
.Sy .META
as a dependency.
.It
[requires
.Xr filemon 4 ]
Files read, executed or linked to are newer than the target.
.It
[requires
.Xr filemon 4 ]
Files read, written, executed or linked are missing.
.El
The meta files can also be useful for debugging.
.Pp
The build will hide commands ran unless
.Va NO_SILENT
is defined.
.Pp
The build operates as it normally would otherwise.
This option originally invoked a different build system but that was renamed
to
.Va WITH_DIRDEPS_BUILD .