## Using the compiler

The `csc` compiler driver provides a convenient interface to the basic Scheme-to-C translator (`chicken`) and takes care for compiling and linking the generated C files into executable code. Enter

    csc -help

on the command line for a list of options.

### Compiler command line format

    csc FILENAME-OR-OPTION

`FILENAME` is the pathname of the source file that is to be compiled. A filename argument of `-` (a single dash) specifies that the source text should be read from standard input.

#### Basic command-line options

-analyze-only
  Stop compilation after first analysis pass.
-block
  Enable block-compilation. When this option is specified, the compiler assumes that global variables are not modified outside this compilation-unit. Specifically, toplevel bindings are not seen by `eval` and unused toplevel bindings are removed.
-case-insensitive
  Enables the reader to read symbols case insensitive. The default is to read case sensitive (in violation of R5RS). This option registers the `case-insensitive` feature identifier.
-check-syntax
  Aborts compilation process after macro-expansion and syntax checks.
-clustering
  Combine groups of local procedures into dispatch-loops, if possible.
-consult-inline-file FILENAME
  load file with definitions for cross-module inlining generated by a previous compiloer invocation via `-emit-inline-file`. Implies `-inline`.
-debug MODES
  Enables one or more compiler debugging modes. `MODES` is a string of characters that select debugging information about the compiler that will be printed to standard output. Use `-debug h` to see a list of available debugging options.
-debug-level LEVEL
  Selects amount of debug-information. `LEVEL` should be an integer.

        -debug-level 0             is equivalent to -no-trace -no-lambda-info
        -debug-level 1             is equivalent to -no-trace
        -debug-level 2             is equivalent to -scrutinize

-disable-interrupts
  Equivalent to the `(disable-interrupts)` declaration. No interrupt-checks are generated for compiled programs.
-disable-stack-overflow-checks
  Disables detection of stack overflows. This is equivalent to running the compiled executable with the `-:o` runtime option.
-dynamic
  This option should be used when compiling files intended to be loaded dynamically into a running Scheme program.
-epilogue FILENAME
  Includes the file named `FILENAME` at the end of the compiled source file. The include-path is not searched. This option may be given multiple times.
-emit-all-import-libraries
  emit import libraries for all modules defined in the current compulation unit (see also: `-emit-import-library`).
-emit-external-prototypes-first
  Emit prototypes for callbacks defined with `define-external` before any other foreign declarations. This is sometimes useful, when C/C++ code embedded into the a Scheme program has to access the callbacks. By default the prototypes are emitted after foreign declarations.
-emit-import-library MODULE
  Specifies that an import library named `MODULE.import.scm` for the named module should be generated (equivalent to using the `emit-import-library` declaration).
-emit-inline-file FILENAME
  Write procedures that can be globally inlined in internal form to `FILENAME`, if global inlining is enabled. Implies `-inline -local`. If the inline-file would be empty (because no procedure would be inlinable) no file is generated and any existing inline-file with that name is deleted.
-emit-type-file FILENAME
  Write type-information for declarations of user-defined and globally visible variables to a file of the given name. The generated file is suitable for use with the `-types` option.
-explicit-use
  Disables automatic use of the units `library, eval` and `extras`. Use this option if compiling a library unit instead of an application unit.
-extend FILENAME
  Loads a Scheme source file or compiled Scheme program (on systems that support it) before compilation commences. This feature can be used to extend the compiler. This option may be given multiple times. The file is also searched in the current include path and in the extension-repository.
-feature SYMBOL
  Registers `SYMBOL` to be a valid feature identifier for `cond-expand`. Multiple symbols may be given, if comma-separated.
-fixnum-arithmetic
  Equivalent to `(fixnum-arithmetic)` declaration. Assume all mathematical operations use small integer arguments.
-heap-size NUMBER
  Sets a fixed heap size of the generated executable to `NUMBER` bytes. The parameter may be followed by a `M` (`m`) or `K` (`k`) suffix which stand for mega- and kilobytes, respectively. The default heap size is 5 kilobytes. Note that only half of it is in use at every given time.
-help
  Print a summary of available options and the format of the command line parameters and exit the compiler.
-ignore-repository
  Do not load any extensions from the repository (treat repository as empty). Also do not consult compiled (only interpreted) import libraries in `import` forms.
-include-path PATHNAME
  Specifies an additional search path for files included via the `include` special form. This option may be given multiple times. If the environment variable `CHICKEN_INCLUDE_PATH` is set, it should contain a list of alternative include pathnames separated by `;`.
-inline
  Enable procedure inlining for known procedures of a size below the threshold (which can be set through the `-inline-limit` option).
-inline-global
  Enable cross-module inlining (in addition to local inlining). Implies `-inline`. For more information, see also Declarations.
-inline-limit THRESHOLD
  Sets the maximum size of a potentially inlinable procedure. The default threshold is `20`.
-keyword-style STYLE
  Enables alternative keyword syntax, where `STYLE` may be either `prefix` (as in Common Lisp, e.g. :keyword), `suffix` (as in DSSSL, e.g. keyword:) or `none`. Any other value is ignored. The default is `suffix`.
-keep-shadowed-macros
  Do not remove macro definitions with the same name as assigned toplevel variables (the default is to remove the macro definition).
-local
  Assume toplevel variables defined in the current compilation unit are not externally modified. This gives the compiler more opportunities for inlining. Note that this may result in counter-intuitive and non-standard behaviour: an asssignment to an exported toplevel variable executed in a different compilation unit or in evaluated code will possibly not be seen by code executing in the current compilation unit.
-lfa2
  Does an additional lightweight flow-analysis pass on the fully optimized program to remove more type checks.
-module
  wraps the compiled code in an implicit module named `main`, importing the `scheme` and `chicken` modules.
-no-argc-checks
  disable argument count checks
-no-bound-checks
  disable bound variable checks
-no-feature SYMBOL
  Disables the predefined feature-identifier `SYMBOL`. Multiple symbols may be given, if comma-separated.
-no-lambda-info
  Don't emit additional information for each `lambda` expression (currently the argument-list, after alpha-conversion/renaming).
-no-module-registration
  Do not generate module-registration code in the compiled code. This is only needed if you want to use an import library that is generated by other means (manually, for example).
-no-parentheses-synonyms
  Disables list delimiter synonyms, [..] and {...} for (...).
-no-procedure-checks
  disable procedure call checks
-no-procedure-checks-for-usual-bindings
  disable procedure call checks only for usual bindings
-no-procedure-checks-for-toplevel-bindings
  disable bound and procedure call checks for calls to procedures referenced through a toplevel variable.
-no-symbol-escape
  Disables support for escaped symbols, the |...| form.
-no-trace
  Disable generation of tracing information. If a compiled executable should halt due to a runtime error, then a list of the name and the line-number (if available) of the last procedure calls is printed, unless `-no-trace` is specified. With this option the generated code is slightly faster.
-no-warnings
  Disable generation of compiler warnings.
-nursery NUMBER
-stack-size NUMBER
  Sets the size of the first heap-generation of the generated executable to `NUMBER` bytes. The parameter may be followed by a `M` (`m`) or `K` (`k`) suffix. The default stack-size depends on the target platform.
-optimize-leaf-routines
  Enable leaf routine optimization.
-optimize-level LEVEL
  Enables certain sets of optimization options. `LEVEL` should be an integer.

        -optimize-level 0          is equivalent to -no-usual-integrations -no-compiler-syntax
        -optimize-level 1          is equivalent to -optimize-leaf-routines
        -optimize-level 2          is equivalent to -optimize-leaf-routines -inline
        -optimize-level 3          is equivalent to -optimize-leaf-routines -local -inline -inline-global -specialize
        -optimize-level 4          is equivalent to -optimize-leaf-routines -local -inline -inline-global -specialize -unsafe
        -optimize-level 5          is equivalent to -optimize-leaf-routines -block -inline -inline-global -specialize -unsafe -disable-interrupts -no-trace -no-lambda-info -clustering -lfa2

-output-file FILENAME
  Specifies the pathname of the generated C file. Default is `FILENAME.c`.
-postlude EXPRESSIONS
  Add `EXPRESSIONS` after all other toplevel expressions in the compiled file. This option may be given multiple times. Processing of this option takes place after processing of `-epilogue`.
-prelude EXPRESSIONS
  Add `EXPRESSIONS` before all other toplevel expressions in the compiled file. This option may be given multiple times. Processing of this option takes place before processing of `-prologue`.
-profile
-accumulate-profile
  Instruments the source code to count procedure calls and execution times. After the program terminates (either via an explicit `exit` or implicitly), profiling statistics are written to a file named `PROFILE.<randomnumber>`. Each line of the generated file contains a list with the procedure name, the number of calls and the time spent executing it. Use the `chicken-profile` program to display the profiling information in a more user-friendly form. Enter `chicken-profile -help` at the command line to get a list of available options. The `-accumulate-profile` option is similar to `-profile`, but the resulting profile information will be appended to any existing `PROFILE` file. `chicken-profile` will merge and sum up the accumulated timing information, if several entries for the same procedure calls exist. Only profiling information for global procedures will be collected.
-profile-name FILENAME
  Specifies name of the generated profile information (which defaults to `PROFILE.<randomnumber>`. Implies `-profile`.
-prologue FILENAME
  Includes the file named `FILENAME` at the start of the compiled source file. The include-path is not searched. This option may be given multiple times.
-r5rs-syntax
  Disables the Chicken extensions to R5RS syntax. Does not disable non-standard read syntax.
-raw
  Disables the generation of any implicit code that uses the Scheme libraries (that is all runtime system files besides `runtime.c` and `chicken.h`).
-require-extension NAME
  Loads the extension `NAME` before the compilation process commences. This is identical to adding `(require-extension NAME)` at the start of the compiled program. If `-uses NAME` is also given on the command line, then any occurrences of `-require-extension NAME` are replaced with `(declare (uses NAME))`. Multiple names may be given and should be separated by commas.
-setup-mode
  When locating extension, search the current directory first. By default, extensions are located first in the extension repository, where `chicken-install` stores compiled extensions and their associated metadata.
-specialize
  Enable simple flow-analysis for doing some type-directed optimizations.
-strict-types
  Assume that the type of variables is not changed by assignments. This gives more type-information during specialization, but violating this assumption will result in unsafe and incorrectly behaving code.
-types FILENAME
  load additional type database from `FILENAME`. Type-definitions in `FILENAME` will override previous type-definitions.
-compile-syntax
  Makes macros also available at run-time. By default macros are not available at run-time.
-to-stdout
  Write compiled code to standard output instead of creating a `.c` file.
-unit NAME
  Compile this file as a library unit. Equivalent to `-prelude "(declare (unit NAME))"`
-unsafe
  Disable runtime safety checks.
-uses NAME
  Use definitions from the library unit `NAME`. This is equivalent to `-prelude "(declare (uses NAME))"`. Multiple arguments may be given, separated by `,`.
-no-usual-integrations
  Specifies that standard procedures and certain internal procedures may be redefined, and can not be inlined. This is equivalent to declaring `(not usual-integrations)`.
-version
  Prints the version and some copyright information and exit the compiler.
-verbose
  enables output of notes that are not necessarily warnings but might be of interest.

The environment variable `CHICKEN_OPTIONS` can be set to a string with default command-line options for the compiler.

#### Further options

Enter

     csc -help

to see a list of all supported options and short aliases to basic options.

### Runtime options

After successful compilation a C source file is generated and can be compiled with a C compiler. Executables generated with CHICKEN (and the compiler itself) accept a small set of runtime options:

`-:?`
  Shows a list of the available runtime options and exits the program.
`-:aNUMBER`
  Specifies the length of the buffer for recording a trace of the last invoked procedures. Defaults to 16.
`-:b`
  Enter a read-eval-print-loop when an error is encountered.
`-:B`
  Sounds a bell (ASCII 7) on every major garbage collection.
`-:c`
  Forces console mode. Currently this is only used in the interpreter (`csi`) to force output of the `#;N>` prompt even if stdin is not a terminal (for example if running in an `emacs` buffer under Windows).
`-:d`
  Prints some debug-information at runtime.
`-:D`
  Prints some more debug-information at runtime.
`-:g`
  Prints information about garbage-collection.
`-:G`
  Force GUI mode (show error messages in dialog box, suitable for platform).
`-:H`
  Before terminating, dump heap usage to stderr.
`-:fNUMBER`
  Specifies the maximal number of currently pending finalizers before finalization is forced.
`-:hNUMBER`
  Specifies fixed heap size
`-:hgPERCENTAGE`
  Sets the growth rate of the heap in percent. If the heap is exhausted, then it will grow by `PERCENTAGE`. The default is 200.
`-:hiNUMBER`
  Specifies the initial heap size
`-:hmNUMBER`
  Specifies a maximal heap size. The default is (2GB - 15).
`-:hsPERCENTAGE`
  Sets the shrink rate of the heap in percent. If no more than a quarter of `PERCENTAGE` of the heap is used, then it will shrink to `PERCENTAGE`. The default is 50. Note: If you want to make sure that the heap never shrinks, specify a value of `0`. (this can be useful in situations where an optimal heap-size is known in advance).
`-:o`
  Disables detection of stack overflows at run-time.
`-:r`
  Writes trace output to stderr. This option has no effect with in files compiled with the `-no-trace` options.
`-:sNUMBER`
  Specifies stack size.
`-:tNUMBER`
  Specifies symbol table size.
`-:w`
  Enables garbage collection of unused symbols. By default unused and unbound symbols are not garbage collected.
`-:x`
  Raises uncaught exceptions of separately spawned threads in primordial thread. By default uncaught exceptions in separate threads are not handled, unless the primordial one explicitly joins them. When warnings are enabled (the default) and `-:x` is not given, a warning will be shown, though.

The argument values may be given in bytes, in kilobytes (suffixed with `K` or `k`), in megabytes (suffixed with `M` or `m`), or in gigabytes (suffixed with `G` or `g`). Runtime options may be combined, like `-:dc`, but everything following a `NUMBER` argument is ignored. So `-:wh64m` is OK, but `-:h64mw` will not enable GC of unused symbols.

### Examples

#### A simple example (with one source file)

To compile a Scheme program (assuming a UNIX-like environment) consisting of a single source file, perform the following steps.

##### Writing your source file

In this example we will assume your source file is called `foo.scm`:

    ;;; foo.scm

    (define (fac n)
      (if (zero? n)
          1
          (* n (fac (- n 1))) ) )

    (write (fac 10))
    (newline)

##### Compiling your program

Compile the file `foo.scm`:

    % csc foo.scm

This will produce the `foo` executable:

    % ls
    foo  foo.scm

##### Running your program

To run your newly compiled executable use:

    % ./foo
    3628800

#### An example with multiple files

If multiple bodies of Scheme code are to be combined into a single executable, then we have to compile each file and link the resulting object files together with the runtime system.

Let's consider an example where your program consists of multiple source files.

##### Writing your source files

The declarations in these files specify which of the compiled files is the main module, and which is the library module. An executable can only have one main module, since a program has only a single entry-point. In this case `foo.scm` is the main module, because it doesn't have a `unit` declaration:

    ;;; foo.scm

    ; The declaration marks this source file as dependant on the symbols provided
    ; by the bar unit:
    (declare (uses bar))

    (write (fac 10)) (newline)

`bar.scm` will be our library:

    ;;; bar.scm

    ; The declaration marks this source file as the bar unit.  The names of the
    ; units and your files don't need to match.
    (declare (unit bar))

    (define (fac n)
      (if (zero? n)
          1
          (* n (fac (- n 1))) ) )

##### Compiling and running your program

You should compile your two files with the following commands:

    % csc -c bar.scm
    % csc -c foo.scm

That should produce two files, `bar.o` and `foo.o`. They contain the code from your source files in compiled form.

To link your compiled files use the following command:

    % csc foo.o bar.o -o foo

This should produce the `foo` executable, which you can run just as in the previous example. At this point you can also erase the `*.o` files.

You could avoid one step and link the two files just as `foo.scm` is compiled:

    % csc -c bar.scm
    % csc foo.scm bar.o -o foo

Note that if you want to distribute your program, you might want it to follow the GNU Coding Standards. One relatively easy way to achieve this is to use Autoconf and Automake, two tools made for this specific purpose.

### Extending the compiler

The compiler supplies a couple of hooks to add user-level passes to the compilation process. Before compilation commences any Scheme source files or compiled code specified using the `-extend` option are loaded and evaluated. The parameters `user-options-pass, user-read-pass, user-preprocessor-pass, user-pass` and `user-post-analysis-pass` can be set to procedures that are called to perform certain compilation passes instead of the usual processing (for more information about parameters see: Supported language.

`user-options-pass` parameter

  Holds a procedure that will be called with a list of command-line arguments and should return two values: the source filename and the actual list of options, where compiler switches have their leading `-` (hyphen) removed and are converted to symbols. Note that this parameter is invoked before processing of the `-extend` option, and so can only be changed in compiled user passes.

`user-read-pass` parameter

  Holds a procedure of three arguments. The first argument is a list of strings with the code passed to the compiler via `-prelude` options. The second argument is a list of source files including any files specified by `-prologue` and `-epilogue`. The third argument is a list of strings specified using `-postlude` options. The procedure should return a list of toplevel Scheme expressions.

`user-preprocessor-pass` parameter

  Holds a procedure of one argument. This procedure is applied to each toplevel expression in the source file before macro-expansion. The result is macro-expanded and compiled in place of the original expression.

`user-pass` parameter

  Holds a procedure of one argument. This procedure is applied to each toplevel expression after macro-expansion. The result of the procedure is then compiled in place of the original expression.

`user-post-analysis-pass` parameter

  Holds a procedure that will be called after every performed program analysis pass. The procedure (when defined) will be called with seven arguments: a symbol indicating the analysis pass, the program database, the current node graph, a getter and a setter-procedure which can be used to access and manipulate the program database, which holds various information about the compiled program, a pass iteration count, and an analysis continuation flag. The getter procedure should be called with two arguments: a symbol representing the binding for which information should be retrieved, and a symbol that specifies the database-entry. The current value of the database entry will be returned or `#f`, if no such entry is available. The setter procedure is called with three arguments: the symbol and key and the new value. The pass iteration count currently is meaningful only for the 'opt pass. The analysis continuation flag will be `#f` for the last 'opt pass. For information about the contents of the program database contact the author.

  Loaded code (via the `-extend` option) has access to the library units `extras, srfi-1, srfi-4, utils, regex` and the pattern matching macros. Multithreading is not available.

  Note that the macroexpansion/canonicalization phase of the compiler adds certain forms to the source program. These extra expressions are not seen by `user-preprocessor-pass` but by `user-pass`.

### Distributing compiled C files

It is relatively easy to create distributions of Scheme projects that have been compiled to C. The runtime system of CHICKEN consists of only three handcoded C files (`runtime.c` and `chicken.h`), plus the file `chicken-config.h`, which is generated by the build process. All other modules of the runtime system and the extension libraries are just compiled Scheme code.The following example shows a minimal application, which should run without changes on the most frequent operating systems, like Windows, Linux or FreeBSD (Static binaries are NOT supported on Mac OS X):

Let's take a simple example.

    ; hello.scm

    (print "Hello, world!")

     % csc -t hello.scm -optimize-level 3 -output-file hello.c

Compiled to C, we get `hello.c`. We need the files `chicken.h`, `chicken-config.h` and `runtime.c`, which contain the basic runtime system, plus the five basic library files `library.c`, `eval.c`, `expand.c`, `modules.c` and `build-version.c` which contain the same functionality as the library linked into a plain CHICKEN-compiled application, or which is available by default in the interpreter, `csi`:

     % cd /tmp
     % echo '(print "Hello World.")' > hello.scm
     % cp $CHICKEN_BUILD/runtime.c  .
     % cp $CHICKEN_BUILD/library.c  .
     % cp $CHICKEN_BUILD/eval.c     .
     % cp $CHICKEN_BUILD/extras.c   .
     % cp $CHICKEN_BUILD/expand.c   .
     % cp $CHICKEN_BUILD/modules.c  .
     % cp $CHICKEN_BUILD/chicken.h  .
     % cp $CHICKEN_BUILD/chicken-config.h  .
     % cp $CHICKEN_BUILD/buildtag.h  .
     % gcc -static -Os -fomit-frame-pointer -DHAVE_CHICKEN_CONFIG_H runtime.c build-version.c \
        library.c eval.c expand.c modules.c hello.c -o hello -lm

Now we have all files together, and can create an tarball containing all the files:

    % tar cf hello.tar hello.c runtime.c build-version.c library.c eval.c extras.c \
      expand.c modules.c chicken.h chicken-config.h
    % gzip hello.tar

This is naturally rather simplistic. Things like enabling dynamic loading, estimating the optimal stack-size and selecting supported features of the host system would need more configuration- and build-time support. All this can be addressed using more elaborate build-scripts, makefiles or by using autoconf/automake.

The `chicken-config.h` file may contain wrong settings for your deployment target. Especially when the architecture is different. In that case you will have to adjust the values as needed.

Note also that the size of the application can still be reduced by removing `eval` and compiling `hello.scm` with the `-explicit-use` option.

For more information, study the CHICKEN source code and/or ask on the CHICKEN mailing list.

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