== Module version

A module version represents a distinct set of changes of a released <<#sub:terminology_module,module>>.
For example `18.0` represents the version of the module with the coordinates `com.google:guava:18.0`.
In practice there's no limitation to the scheme of the module version.
Timestamps, numbers, special suffixes like `-GA` are all allowed identifiers.
The most widely-used versioning strategy is link:https://semver.org/[semantic versioning].

		// the environment in any case, as Go represents the
		// environment as a slice of "key=value" strings.
		return '_'
	}
	// TODO: other transformations in spec or practice?
	return r
}

      if (rule != null) {
        exactMatch = rule
        break
      }
    }

    // In theory, wildcard rules are not restricted to having the wildcard in the leftmost position.
    // In practice, wildcards are always in the leftmost position. For now, this implementation
    // cheats and does not attempt every possible permutation. Instead, it only considers wildcards

				// sorts and deduplicates the values, so we need to make sure ours are
				// sorted and deduplicated as well here to preserve round-trip comparison.
				// In practice, not sorting doesn't hurt anything...

				for i := range j.MatchExpressions {
					req := metav1.LabelSelectorRequirement{}
					c.Fuzz(&req)
					req.Key = randomLabelKey(c)

[[sub:ephemeral-ci-cache]]
== Dealing with ephemeral builds

It's a common practice to run builds in ephemeral containers.
A container is typically spawned to only execute a single build before it is destroyed.
This can become a practical problem when a build depends on a lot of dependencies which each container has to re-download.

//
// Because slices aren't comparable and we want to leverage maps for deduplication,
// we have to choose a fixed constant upper bound on the amount of frames we want
// to support. In practice this is fine because there's a maximum depth to these
// stacks anyway.
const pprofMaxStack = 128

// stackMap is a map of trace.Stack to some value V.
type stackMap struct {

			return mailbox, false
		}
	}

	if len(in) == 0 || in[0] != '@' {
		return mailbox, false
	}
	in = in[1:]

	// The RFC species a format for domains, but that's known to be
	// violated in practice so we accept that anything after an '@' is the
	// domain part.
	if _, ok := domainToReverseLabels(in); !ok {
		return mailbox, false
	}

	mailbox.local = string(localPartBytes)
	mailbox.domain = in

// The death testing framework causes this to have interesting semantics,
// since the sideeffects of the call are only visible in opt mode, and not
// in debug mode.
//
// In practice, this can be used to test functions that utilize the
// LOG(DFATAL) macro using the following style:
//
// int DieInDebugOr12(int* sideeffect) {
//   if (sideeffect) {
//     *sideeffect = 12;
//   }

	// However, in practice, that seems not to happen too much.
	// Most build graphs are surprisingly serial, so p==1 for much of the build.
	// Furthermore, concurrent backend compilation is only enabled for a part
	// of the overall compiler execution, so c==1 for much of the build.
	// So don't worry too much about that interaction for now.
	//
	// However, in practice, setting c above 4 tends not to help very much.

		indexers[indexName] = c.objInfoIndexFunc
	}
	c.store = cache.NewIndexer(objInfoKeyFunc, indexers)

	// Unit tests don't use informers
	if informer != nil {
		// Cannot fail in practice?! No-one bothers checking the error.
		_, _ = informer.AddEventHandler(
			cache.ResourceEventHandlerFuncs{
				AddFunc:    c.add,
				UpdateFunc: c.update,
				DeleteFunc: c.delete,
			},
		)
	}