— Function: sb-ext:save-lisp-and-die core-file-name &key toplevel purify root-structures environment-name

Save a "core image", i.e. enough information to restart a Lisp process later in the same state, in the file of the specified name. Only global state is preserved: the stack is unwound in the process.

The following &KEY arguments are defined:

:toplevel

The function to run when the created core file is resumed. The default function handles command line toplevel option processing and runs the top level read-eval-print loop. This function should not return.

:purify

If true (the default on cheneygc), do a purifying gc which moves all dynamically allocated objects into static space. This takes somewhat longer than the normal gc which is otherwise done, but it's only done once, and subsequent GC's will be done less often and will take less time in the resulting core file. See the purify function. For platforms that use the generational garbage collector (x86 and x86-64) purification generally results in a loss of performance.

:root-structures

This should be a list of the main entry points in any newly loaded systems. This need not be supplied, but locality and/or gc performance may be better if they are. Meaningless if :purify is nil. See the purify function.

:environment-name

This is also passed to the purify function when :purify is t. (rarely used)

The save/load process changes the values of some global variables:

*standard-output*, *debug-io*, etc.

Everything related to open streams is necessarily changed, since the os won't let us preserve a stream across save and load.

*default-pathname-defaults*

This is reinitialized to reflect the working directory where the saved core is loaded.

Foreign objects loaded with sb-alien:load-shared-object are automatically reloaded on startup, but references to foreign symbols do not survive intact on all platforms: in this case a warning is signalled when saving the core. If no warning is signalled, then the foreign symbol references will remain intact. Platforms where this is currently the case are x86/FreeBSD, x86/Linux, x86/NetBSD, sparc/Linux, sparc/SunOS, and ppc/Darwin.

This implementation is not as polished and painless as you might like:

• It corrupts the current Lisp image enough that the current process needs to be killed afterwards. This can be worked around by forking another process that saves the core.
• It will not work if multiple threads are in use.
• There is absolutely no binary compatibility of core images between different runtime support programs. Even runtimes built from the same sources at different times are treated as incompatible for this purpose.

This isn't because we like it this way, but just because there don't seem to be good quick fixes for either limitation and no one has been sufficiently motivated to do lengthy fixes.