Installing Scheme48: Details

Here are some remarks to complement what's in the INSTALL file.

When running "make", don't worry if the ".notify" target fails. Its only purpose is to send an email message to scheme-48-notifications@martigny.ai.mit.edu, so that we can get a rough idea of how much Scheme 48 is being used and by whom. We promise not to use your name or email address for any commercial purpose. If you don't want us to know, just do "make -t .notify" first.

Customizing the installation

Customizing scheme48.image

By default, the image consists of a core Scheme system (Revised^4 Scheme plus a very minimal read-eval-print loop) together with a standard set of "options" (command processor, debugging commands, inspector, disassembler, generic arithmetic). The set of options is controlled by the definitions of USUAL-COMMANDS and USUAL-FEATURES in more-packages.scm. If you make the (open ...) clause empty, then "make scheme48.image" will create a Scheme system without any extras (such as error recovery), and the image will be smaller. The files are listed in approximate order of decreasing desirability; you'll probably want at least these:

package-commands, build
necessary for the scheme48.image script to work

debuginfo, disclosers
necessary if you want error messages to be at all helpful

defines important debugging commands such as ,preview and ,trace

After editing the definition of usual-features, simply

        make scheme48.image

to rebuild the image.

Deeper changes to the system -- for example, edits to most of the files in the rts/ directory -- will require using the static linker to make a new initial.image. After you have a working scheme48.image (perhaps a previous version of Scheme 48), you can create a linker image with

        make linker

after which you can say

        make image

to get the linker to build a new initial.image and initial.debug. scheme48.image will then be built from those.

You might think that "make scheme48.image" ought to do this, but the circular dependencies

needs to be broken somewhere, or else make will (justifiably) barf. I chose to break the cycle by making scheme48.image not depend on initial.image, since this is most robust for installation purposes.

Editor support

We recommend interacting with the Scheme 48 command processor using the emacs/scheme interface written by Olin Shivers at CMU. Copies of the relevant .el files, together with a "cmuscheme48.el", are in the emacs/ subdirectory of the release. Usage information is in doc/user-guide.txt.

You will probably want to byte-compile the .el files to get .elc files. Use M-x byte-compile-file to do this.


If you don't have a C compiler that optimizes as well as gcc does, then performance may suffer. Take a look at the automatically generated code in scheme48vm.c to find out why. With a good register allocator, all those variables (including some of the virtual machine's virtual registers) get allocated to hardware registers, and it really flies. Without one, performance can be pretty bad.

The configure script automatically sets the Makefile variable CFLAGS to -O2 -g if gcc is available, or to -O if it isn't. This can be overriden by specifying a different CFLAGS, e.g. "make CFLAGS=-g" for no optimization.

Even if you do have a good compiler, you should be able to improve overall performance even more, maybe about 6-10%, by removing the range check from the interpreter's instruction dispatch. To do this, use the -S flag to get assembly code for scheme48vm.c, then find the instructions in scheme48vm.s corresponding to the big dispatch in Tinterpret():

  b_111X = *((unsigned char*) RScode_pointerS);
  RScode_pointerS = (1 + RScode_pointerS);
  switch (b_111X) {
    ... }

There will be one or two comparison instructions to see whether b_113X is in range; just remove them. For the 68000 I use a "sed" script

    /cmpl #137,d0/ N
    /cmpl #137,d0\n     jhi L/ d

but of course the constant will probably have to change when a new release comes along.

See the user's guide for information on the ,bench command, which makes programs run faster.


filenames.make is "include"d by the Makefile, but is automatically generated from the module dependencies laid out in the various configuration files (*-packages.scm). If you edit any of these .scm files, you may want to do a "make filenames.make" before you do any further "make"s in order to update the depedencies. This step isn't necessary if you're using Gnu make, because Gnu make will make included files automatically.


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