1 raco make: Compiling Source to Bytecode

The raco make command accept filenames for Racket modules to be compiled to bytecode format. Modules are re-compiled only if the source Racket file is newer than the bytecode file and has a different SHA-1 hash, or if any imported module is recompiled or has a different SHA-1 hash for its compiled form plus dependencies.

1.1 Bytecode Files

A file "‹name›.‹ext›" is compiled to bytecode that is saved as "compiled/‹name›_‹ext›.zo" relative to the file. As a result, the bytecode file is normally used automatically when "‹name›.‹ext›" is required as a module, since the underlying load/use-compiled operation detects such a bytecode file.

For example, in a directory that contains the following files:

• "a.rkt":

  #lang racket

  (require "b.rkt" "c.rkt")

  (+ b c)

• "b.rkt":

  #lang racket

  (provide b)

  (define b 1)

• "c.rkt":

  #lang racket

  (provide c)

  (define c 1)

then

  raco make a.rkt

triggers the creation of "compiled/a_rkt.zo", "compiled/b_rkt.zo", and "compiled/c_rkt.zo". A subsequent

  racket a.rkt

loads bytecode from the generated ".zo" files, paying attention to the ".rkt" sources only to confirm that each ".zo" file has a later timestamp.

In contrast,

  racket b.rkt c.rkt

would create only "compiled/b_rkt.zo" and "compiled/c_rkt.zo", since neither "b.rkt" nor "c.rkt" imports "a.rkt".

1.2 Dependency Files

In addition to a bytecode file, raco make creates a file "compiled/‹name›_‹ext›.dep" that records dependencies of the compiled module on other module files and the source file’s SHA-1 hash. Using this dependency information, a re-compilation request via raco make can consult both the source file’s timestamp/hash and the timestamps/hashes for the bytecode of imported modules. Furthermore, imported modules are themselves compiled as necessary, including updating the bytecode and dependency files for the imported modules, transitively.

Continuing the raco make a.rkt example from the previous section, the raco make command creates "compiled/a_rkt.dep", "compiled/b_rkt.dep", and "compiled/c_rkt.dep" at the same time as the ".zo" files. The "compiled/a_rkt.dep" file records the dependency of "a.rkt" on "b.rkt", "c.rkt" and the racket library. If the "b.rkt" file is modified (so that its timestamp and SHA-1 hash changes), then running

  raco make a.rkt

again rebuilds "compiled/a_rkt.zo" and "compiled/b_rkt.zo".

For module files that are within library collections, raco setup uses the same ".zo" and ".dep" conventions and files as raco make, so the two tools can be used together.

1.3 API for Making Bytecode

• the file is expected to contain a module (i.e., the second argument to the handler is a symbol);

• the value of each of (current-eval), (current-load), and (namespace-module-registry (current-namespace)) is the same as when make-compilation-manager-load/use-compiled-handler was called;

• the value of use-compiled-file-paths contains the first path that was present when make-compilation-manager-load/use-compiled-handler was called;

• the value of current-load/use-compiled is the result of this procedure; and

• one of the following holds:

  • the source file is newer than the ".zo" file in the first sub-directory listed in use-compiled-file-paths (at the time that make-compilation-manager-load/use-compiled-handler was called), and either no ".dep" file exists or it records a source-file SHA-1 hash that differs from the current version and source-file SHA-1 hash;

  • no ".dep" file exists next to the ".zo" file;

  • the version recorded in the ".dep" file does not match the result of (version);

  • one of the files listed in the ".dep" file has a ".zo" timestamp newer than the target ".zo", and the combined hashes of the dependencies recorded in the ".dep" file does not match the combined hash recorded in the ".dep" file.

If SHA-1 hashes override a timestamp-based decision to recompile the file, then the target ".zo" file’s timestamp is updated to the current time.

After the handler procedure compiles a ".zo" file, it creates a corresponding ".dep" file that lists the current version and the identification of every file that is directly required by the module in the compiled file. Additional dependencies can be installed during compilation via compiler/cm-accomplice. The ".dep" file also records the SHA-1 hash of the module’s source, and it records a combined SHA-1 hash of all of the dependencies that includes their recursive dependencies.

The handler caches timestamps when it checks ".dep" files, and the cache is maintained across calls to the same handler. The cache is not consulted to compare the immediate source file to its ".zo" file, which means that the caching behavior is consistent with the caching of the default module name resolver (see current-module-name-resolver).

If use-compiled-file-paths contains an empty list when make-compilation-manager-load/use-compiled-handler is called, then exn:fail:contract exception is raised.

Do not install the result of make-compilation-manager-load/use-compiled-handler when the current namespace contains already-loaded versions of modules that may need to be recompiled – unless the already-loaded modules are never referenced by not-yet-loaded modules. References to already-loaded modules may produce compiled files with inconsistent timestamps and/or ".dep" files with incorrect information.

If file is compiled from source, then read-src-syntax is used in the same way as read-syntax to read the source module. The normal read-syntax is used for any required files, however.

This function is intended for use with manager-skip-file-handler.

1.4 Compilation Manager Hook for Syntax Transformers

(require compiler/cm-accomplice)

A compilation manager implemented by compiler/cm looks for such messages to register an external dependency. The compilation manager records (in a ".dep" file) the path as contributing to the implementation of the module currently being compiled. Afterward, if the registered file is modified, the compilation manager will know to recompile the module.

The include macro, for example, calls this procedure with the path of an included file as it expands an include form.

1.5 Compiling to Raw Bytecode

The --zo/-z mode for raco make is an improverished form of the compilation, because it does not track import dependencies. It does, however, support compilation of non-module source.

By default, the generated bytecode is placed in the same directory as the source file – which is not where it will be found automatically when loading the source. Use the --auto-dir flag to redirect the output to a "compiled" subdirectory, where it will be found automatically when loading the source file.

Outside of a module, top-level define-syntaxes, module, #%require, define-values-for-syntax, and and begin expressions are handled specially by raco make --zo: the compile-time portion of the expression is evaluated, because it might affect later expressions. (The -m or --module flag turns off this special handling.)

For example, when compiling the file containing

(require racket/class)

(define f (class% object% (super-new)))

the class form from the racket/class library must be bound in the compilation namespace at compile time. Thus, the require expression is both compiled (to appear in the output code) and evaluated (for further computation).

Many definition forms expand to define-syntaxes. For example, define-signature expands to define-syntaxes. In --zo mode, raco make --zo detects define-syntaxes and other expressions after expansion, so top-level define-signature expressions affect the compilation of later expressions, as a programmer would expect.

In contrast, a load or eval expression in a source file is compiled – but not evaluated! – as the source file is compiled. Even if the load expression loads syntax or signature definitions, these will not be loaded as the file is compiled. The same is true of application expressions that affect the reader, such as (read-case-sensitive #t). The -p or --prefix flag for raco make takes a file and loads it before compiling the source files specified on the command line.

In general, a better solution is to put all code to compile into a module and use raco make in its default mode.