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// Copyright 2021 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
// Package goexperiment implements support for toolchain experiments.
//
// Toolchain experiments are controlled by the GOEXPERIMENT
// environment variable. GOEXPERIMENT is a comma-separated list of
// experiment names. GOEXPERIMENT can be set at make.bash time, which
// sets the default experiments for binaries built with the tool
// chain; or it can be set at build time. GOEXPERIMENT can also be set
// to "none", which disables any experiments that were enabled at
// make.bash time.
//
// Experiments are exposed to the build in the following ways:
//
// - Build tag goexperiment.x is set if experiment x (lower case) is
// enabled.
//
// - For each experiment x (in camel case), this package contains a
// boolean constant x and an integer constant xInt.
//
// - In runtime assembly, the macro GOEXPERIMENT_x is defined if
// experiment x (lower case) is enabled.
//
// In the toolchain, the set of experiments enabled for the current
// build should be accessed via objabi.Experiment.
//
// The set of experiments is included in the output of runtime.Version()
// and "go version <binary>" if it differs from the default experiments.
//
// For the set of experiments supported by the current toolchain, see
// "go doc goexperiment.Flags".
//
// Note that this package defines the set of experiments (in Flags)
// and records the experiments that were enabled when the package
// was compiled (as boolean and integer constants).
//
// Note especially that this package does not itself change behavior
// at run time based on the GOEXPERIMENT variable.
// The code used in builds to interpret the GOEXPERIMENT variable
// is in the separate package internal/buildcfg.
package goexperiment
//go:generate go run mkconsts.go
// Flags is the set of experiments that can be enabled or disabled in
// the current toolchain.
//
// When specified in the GOEXPERIMENT environment variable or as build
// tags, experiments use the strings.ToLower of their field name.
//
// For the baseline experimental configuration, see
// objabi.experimentBaseline.
//
// If you change this struct definition, run "go generate".
type Flags struct {
FieldTrack bool
PreemptibleLoops bool
StaticLockRanking bool
BoringCrypto bool
// Regabi is split into several sub-experiments that can be
// enabled individually. Not all combinations work.
// The "regabi" GOEXPERIMENT is an alias for all "working"
// subexperiments.
// RegabiWrappers enables ABI wrappers for calling between
// ABI0 and ABIInternal functions. Without this, the ABIs are
// assumed to be identical so cross-ABI calls are direct.
RegabiWrappers bool
// RegabiArgs enables register arguments/results in all
// compiled Go functions.
//
// Requires wrappers (to do ABI translation), and reflect (so
// reflection calls use registers).
RegabiArgs bool
// HeapMinimum512KiB reduces the minimum heap size to 512 KiB.
//
// This was originally reduced as part of PacerRedesign, but
// has been broken out to its own experiment that is disabled
// by default.
HeapMinimum512KiB bool
// CoverageRedesign enables the new compiler-based code coverage
// tooling.
CoverageRedesign bool
// Arenas causes the "arena" standard library package to be visible
// to the outside world.
Arenas bool
// PageTrace enables GODEBUG=pagetrace=/path/to/result. This feature
// is a GOEXPERIMENT due to a security risk with setuid binaries:
// this compels the Go runtime to write to some arbitrary file, which
// may be exploited.
PageTrace bool
// CgoCheck2 enables an expensive cgo rule checker.
// When this experiment is enabled, cgo rule checks occur regardless
// of the GODEBUG=cgocheck setting provided at runtime.
CgoCheck2 bool
// LoopVar changes loop semantics so that each iteration gets its own
// copy of the iteration variable.
LoopVar bool
// CacheProg adds support to cmd/go to use a child process to implement
// the build cache; see https://github.com/golang/go/issues/59719.
CacheProg bool
// NewInliner enables a new+improved version of the function
// inlining phase within the Go compiler.
NewInliner bool
// RangeFunc enables range over func.
RangeFunc bool
// Range enables range over int and func.
Range bool
// AllocHeaders enables a different, more efficient way for the GC to
// manage heap metadata.
AllocHeaders bool
// ExecTracer2 controls whether to use the new execution trace
// implementation.
ExecTracer2 bool
}
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