Compiling Chapel Programs

The Chapel compiler converts programs expressed in Chapel source code into the corresponding executable form. This document briefly discusses running the Chapel compiler.

Getting Help

If you have set up your environment as described in Setting up Your Environment for Chapel and built the compiler as described in Building Chapel, you can see the Chapel compiler’s help message using:

chpl --help

This displays the compiler’s command-line flags sorted by category. For each flag, the short one-letter form is given (if one exists), followed by the long form of the flag. Next, the pattern for any arguments to the flag are given. And finally a brief description of the flag is provided. A flag may have a corresponding environment variable, setting which is equivalent to passing the flag. These variables are listed by the --help-env option. The flags’ current settings are listed by --help-settings.

More detailed information about the compiler and its command-line flags is also available on its man page, which can be viewed from the command-line using:

man chpl

Most Useful Flags

We note some of the most useful flags here:



-o <filename>

specify the filename of the generated executable, otherwise the name of the file containing the main module is used (minus its .chpl extension).


turns off runtime semantic checks like bounds checking and nil class instance dereferencing


turns on optimization of the generated C code


turns on --no-checks, -O, and enables many other optimizations

-s <name[=expr]>

set a config declaration with the given expression as its default value (config params must be set to values that are known at compile time)

--M <dir>

add the specified directory to the module search path

--savec <dir>

saves the generated C code in the specified directory


support debugging of the generated C code

--ccflags <flags>

specify flags that should be used when invoking the back-end C compiler

--ldflags <flags>

specify flags that should be used when invoking the back-end linker


print the compiler passes as they execute


print the system commands that the compiler executes


prints some code size statistics about the number of lexical tokens per line, as well as the number of code, comment, and blank lines


print the Chapel compiler version number


print a brief overview of the command-line options


lists the environment variables for each command-line flag


lists the current setting of each command-line flag

Tab Completion for Flags

Bash users can source the script $CHPL_HOME/util/chpl-completion.bash to enable tab-completion for chpl options. After sourcing the chpl-completion.bash script tab completion can be used:

% chpl --ca<tab><tab>

Will print the options that start with “–ca”.

--cache-remote --cast-checks

Adding one more letter to differentiate and pressing tab again will auto-complete the option and add a space, ready for the next option.

% chpl --cac<tab>
% chpl --cache-remote