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The portable dumper

Olivier Galibert <galibert@pobox.com>

The portable dumper is a subsystem that replaces the traditional ``unexec'' method of creating an Emacs pre-loaded with Lisp code and data. The traditional method actually ``dumps'' the core image of the executable to a file, then adjusts the file so that it can be executed by the operating system, restoring the execution state. The portable dumper executes Emacs as usual, then reloads the Lisp code and data very quickly from a specially formatted dump file. This is not as fast as the unexec method, but it requires much less knowledge of the operating system, and is thus more portable and maintainable.

Status

The pdumper is on by default on all platforms.

The portable dumper code is apparently done. I have had no problems, Michael Sperber reports no problems in execution and a minor one in the build process, and it is a distinct improvement over the traditional dump process on the NT platform. The "buffer locals bug" has been resolved and no others are known.

Olivier has said he doesn't know about anything else, but he (again conservatively) won't rule out other problems. I haven't received a specific statement from him about feasibility for March 1. However, this feature is considered extremely important for the Windows platform, and truly reverting this feature to the status quo ante would require reimplementing pure space, which seems like too much work to be done by March. So defaulting it off on non-Windows platforms seems to be the feasible fallback option.

Open bugs

None.

Other open issues

• The pdumper has cost us ``pure space.'' this bothers Hrvoje, at least.

Discussion

None.

Closed bugs

None.