unikernel/duniverse/cmdliner-stdlib/README.md

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+# cmdliner-stdlib
+
+The `cmdliner-stdlib` package is a collection of cmdliner terms that
+help control OCaml runtime parameters, usually configured through the
+`OCAMLRUNPARAM` environment variable. The package provides command-line
+options for controlling features like backtrace, hash table
+randomization, and garbage collector tuning.
+
+## Installation
+
+You can install the package using `opam`:
+
+```bash
+opam install cmdliner-stdlib
+```
+
+## Usage
+
+You can use these command-line arguments to:
+- enable/disable backtraces;
+- enable/disable table randomization, for better security and prevent
+  collision attacks; and
+- control the OCaml garbage collector as described in detail in the
+  [GC
+  control](http://caml.inria.fr/pub/docs/manual-ocaml/libref/Gc.html#TYPEcontrol)
+  documentation.
+
+```ocaml
+open Cmdliner
+
+let cmd = Cmd.v (Cmd.info "hello") (Cmdliner_stdlib.setup ())
+let () = exit (Cmd.eval cmd)
+```
+
+You can then use command-line options to change parameters of the
+OCaml runtime. For instance, to enable backtraces and change the GC
+allocation policy to "first fit":
+
+```sh
+$ dune exec -- ./hello.exe --allocation-policy=first-fit --backtrace=true
+```
+
+You can disable some of these arguments. For instance, to disable GC control use:
+
+```ocaml
+   Cmdliner_stdlib.setup ~gc_control:None ()
+```
+
+Or to change the default allocation policy to be `first-fit`:
+
+
+```ocaml
+  let default = Gc.get () in
+  let gc_control = Some { default with allocation_policy = 1 } in
+  Cmdliner_stdlib.setup ~gc_control ()
+```
+
+## Contributions
+
+We welcome contributions, bug reports, and feature requests. Please
+visit our [GitHub
+repository](https://github.com/mirage/cmdliner-stdlib) for more
+information.