The runtime system (cslrun)

The cslrun command executes bytecode files produced by the linking phase of the cslc command.

Overview

The cslrun command comprises three main parts: the bytecode interpreter, that actually executes bytecode files; the memory allocator and garbage collector; and a set of C functions that implement primitive operations such as input/output.

The usage for cslrun is:

        cslrun options bytecode-executable arg1 ... argn

As mentioned in chapter , in most cases, the bytecode executable files produced by the cslc command are self-executable, and manage to launch the cslrun command on themselves automatically. That is, assuming caml.out is a bytecode executable file,

        caml.out arg1 ... argn

        cslrun caml.out arg1 ... argn

Options

The following command-line option is recognized by cslrun.

-v

When set, the memory manager prints verbose messages on standard error to signal garbage collections and heap extensions.

The following environment variable are also consulted:

CAMLRUNPARAM

Set the garbage collection parameters. This variable must be a sequence of parameter specifications. A parameter specification is an option letter followed by an = sign and a decimal number. There are four options, corresponding to the four fields of the control record documented in section :

s

(minor_heap_size) Size of the minor heap.

i

(major_heap_increment) Minimum size increment for the major heap.

o

(space_overhead) The major GC speed setting.

v

(verbose) Whether to print GC messages or not. 0 is false; 1 is true; other values may give unexpected results.

For example, under csh the command

        setenv CAMLRUNPARAM 's=250000 v=1'

tells a subsequent cslrun to set its initial minor heap size to about 1 megabyte (on a 32-bit machine) and to print its GC messages.

PATH

List of directories searched to find the bytecode executable file.

Common errors

This section describes and explains the most frequently encountered error messages.

filename: no such file or directory

If filename is the name of a self-executable bytecode file, this means that either that file does not exist, or that it failed to run the cslrun bytecode interpreter on itself. The second possibility indicates that Caml Special Light has not been properly installed on your system.

Cannot exec camlrun

(When launching a self-executable bytecode file.) The cslrun could not be found in the executable path. Check that Caml Special Light has been properly installed on your system.

Cannot find the bytecode file

The file that cslrun is trying to execute (e.g. the file given as first non-option argument to cslrun) either does not exist, or is not a valid executable bytecode file.

Truncated bytecode file

The file that cslrun is trying to execute is not a valid executable bytecode file. Probably it has been truncated or mangled since created. Erase and rebuild it.

Uncaught exception

The program being executed contains a ``stray'' exception. That is, it raises an exception at some point, and this exception is never caught. This causes immediate termination of the program. The name of the exception is printed, but not its arguments.

Out of memory

The program being executed requires more memory than available. Either the program builds excessively large data structures; or the program contains too many nested function calls, and the stack overflows. In some cases, your program is perfectly correct, it just requires more memory than your machine provides. In other cases, the ``out of memory'' message reveals an error in your program: non-terminating recursive function, allocation of an excessively large array or string, attempts to build an infinite list or other data structure, ...

To help you diagnose this error, run your program with the -v option to cslrun. If it displays lots of ``Growing stack...'' messages, this is probably a looping recursive function. If it displays lots of ``Growing heap...'' messages, with the heap size growing slowly, this is probably an attempt to construct a data structure with too many (infinitely many?) cells. If it displays few ``Growing heap...'' messages, but with a huge increment in the heap size, this is probably an attempt to build an excessively large array or string.