-keep-locs Keep locations in .cmi files (default)
-no-keep-locs Do not keep locations in .cmi filesConfigurable Defaults Last updated May 2, 2022
A user-defined build setting, in Bazel’s terminology, is a rule that determines a single piece of configuration information.
A "configuration rule", in OBazl’s terminology, is a build setting rule that is designated as the default value of a rule attribute.
Some OCaml compile options are used so commonly used that they should probably be the default. Changing compiler defaults would break existing code, so OBazl does the next best thing: it defines a set of configuration rules that control the construction of compile commands. These are documented in the rules_ocaml Reference Manual.
Each configuration rule has a default value, which may be globally
overridden on the command line. For example, verbosity is controlled
by flag @ocaml//verbose, which is set to False (disabled) by
default. Each ocaml_* rule examines this flag to decide whether or
not to add -verbose to the build command; setting it to True tells
OBazl to add -verbose to all build commands.
To enable a boolean flag, just pass the flag: --@ocaml//cfg/verbose.
To disable, prefix no to the flag: --no@ocaml//cfg/keep-locs.
| These flags/options apply to rules, and therefore to all instances of the rules. This means that changing one of them will trigger a rebuild of all direct and indirect dependencies of the build target! |
Each flag corresponds to an option that can also be passed via the
opts rule attribute. For example, @ocaml//verbose corresponds to
-verbose, @ocaml//strict-sequence corresponds to
-strict-sequence, and so forth. Usually the correspondance is direct
and obvious; the exception is @ocaml//cmt, which corresponds to
flag -bin-annot, which tells the compiler to emit .cmt/.cmti files as
a side-effect of compilation.
Negation is generally a simple matter of omission. If --@ocaml//foo
adds flag -foo, then --no@ocaml//foo (equivalently
--@ocaml//foo:disable) will prevent addition of that flag. For
example, the -short-paths flag is added to all compile commands by
default, since the default for @ocaml//short-paths is True. Setting
the default to false by passing --no@ocaml//short-paths (or
--@ocaml//short-paths:disable) simply prevents the addition of that
flag.
Case-by-case overrides
These configuration rules - flags and options - have global effect; each
instance of each ocaml_* rule will be controlled by these
flags/options. But they can be overridden on a case-by-case basis by
passing the relevant argument to the opts attribute.
For example, verbosity is globally disabled by default. To enable
verbosity for a particular ocaml_module instance, just add
-verbose to the opts attribute of the rule.
Disabling
Disabling is just as easy, but does not always correspond directly to
OCaml flags. Some OCaml flags support a negating prefix -no; for
example, ocamlopt --help displays the following:
But not all flags support negation in this way; for example, there is
no -no-verbose flag. However, the OBazel opts attribute does
understand such flags, which allows negation for such cases. For
example, suppose verbosity has been globally enabled by passing
--@ocaml//verbose. To disable verbosity for a particular
ocaml_module instance, pass -no-verbose to the opts attribute.
This tells OBazl (not OCaml) to remove the -verbose flag that the
global setting adds.
A -no prefixed flag for the opts attribute is supported for each
configuration rule, just as --no@ocaml//<flag> is supported
for the command-line.
IMPORTANT The authoritative source of documentation for OCaml compile
flags is the compiler --help option. At time of writing, the
official OCaml manual is incomplete (for example, it does not
document -keep-locs).