View source code
Display the source code in rt/config.d from which this page was generated on github.
Report a bug
If you spot a problem with this page, click here to create a Bugzilla issue.
Improve this page
Quickly fork, edit online, and submit a pull request for this page. Requires a signed-in GitHub account. This works well for small changes. If you'd like to make larger changes you may want to consider using local clone.

Module rt.config

Configuration options for druntime.

The default way to configure the runtime is by passing command line arguments starting with --DRT- and followed by the option name, e.g. --DRT-gcopt to configure the GC. Command line options starting with --DRT- are filtered out before calling main, so the program will not see them. They are still available via rt_args().

Configuration via the command line can be disabled by declaring a variable for the linker to pick up before using it's default from the runtime:

extern(C) __gshared bool rt_cmdline_enabled = false;

Likewise, declare a boolean rt_envvars_enabled to enable configuration via the environment variable DRT_ followed by the option name, e.g. DRT_GCOPT:

extern(C) __gshared bool rt_envvars_enabled = true;

Setting default configuration properties in the executable can be done by specifying an array of options named rt_options:

extern(C) __gshared string[] rt_options = [ "gcopt=precise:1 profile:1"];

Evaluation order of options is rt_options, then environment variables, then command line arguments, i.e. if command line arguments are not disabled, they can override options specified through the environment or embedded in the executable.


rt_configOption(opt, dg, reverse) get a druntime config option using standard configuration options opt name of the option to retrieve dg if non-null, passes the option through this delegate and only returns its return value if non-null reverse reverse the default processing order cmdline/envvar/rt_options to allow overwriting settings in the delegate with values from higher priority


Rainer Schuetze


Distributed under the Boost Software License 1.0. (See accompanying file LICENSE)