1 // Copyright 2021 The Go Authors. All rights reserved.
2 // Use of this source code is governed by a BSD-style
3 // license that can be found in the LICENSE file.
5 // Package goexperiment implements support for toolchain experiments.
7 // Toolchain experiments are controlled by the GOEXPERIMENT
8 // environment variable. GOEXPERIMENT is a comma-separated list of
9 // experiment names. GOEXPERIMENT can be set at make.bash time, which
10 // sets the default experiments for binaries built with the tool
11 // chain; or it can be set at build time. GOEXPERIMENT can also be set
12 // to "none", which disables any experiments that were enabled at
15 // Experiments are exposed to the build in the following ways:
17 // - Build tag goexperiment.x is set if experiment x (lower case) is
20 // - For each experiment x (in camel case), this package contains a
21 // boolean constant x and an integer constant xInt.
23 // - In runtime assembly, the macro GOEXPERIMENT_x is defined if
24 // experiment x (lower case) is enabled.
26 // In the toolchain, the set of experiments enabled for the current
27 // build should be accessed via objabi.Experiment.
29 // The set of experiments is included in the output of runtime.Version()
30 // and "go version <binary>" if it differs from the default experiments.
32 // For the set of experiments supported by the current toolchain, see
33 // "go doc goexperiment.Flags".
35 // Note that this package defines the set of experiments (in Flags)
36 // and records the experiments that were enabled when the package
37 // was compiled (as boolean and integer constants).
39 // Note especially that this package does not itself change behavior
40 // at run time based on the GOEXPERIMENT variable.
41 // The code used in builds to interpret the GOEXPERIMENT variable
42 // is in the separate package internal/buildcfg.
45 //go:generate go run mkconsts.go
47 // Flags is the set of experiments that can be enabled or disabled in
48 // the current toolchain.
50 // When specified in the GOEXPERIMENT environment variable or as build
51 // tags, experiments use the strings.ToLower of their field name.
53 // For the baseline experimental configuration, see
54 // objabi.experimentBaseline.
56 // If you change this struct definition, run "go generate".
60 StaticLockRanking bool
63 // Regabi is split into several sub-experiments that can be
64 // enabled individually. Not all combinations work.
65 // The "regabi" GOEXPERIMENT is an alias for all "working"
68 // RegabiWrappers enables ABI wrappers for calling between
69 // ABI0 and ABIInternal functions. Without this, the ABIs are
70 // assumed to be identical so cross-ABI calls are direct.
72 // RegabiArgs enables register arguments/results in all
73 // compiled Go functions.
75 // Requires wrappers (to do ABI translation), and reflect (so
76 // reflection calls use registers).
79 // HeapMinimum512KiB reduces the minimum heap size to 512 KiB.
81 // This was originally reduced as part of PacerRedesign, but
82 // has been broken out to its own experiment that is disabled
84 HeapMinimum512KiB bool
86 // CoverageRedesign enables the new compiler-based code coverage
90 // Arenas causes the "arena" standard library package to be visible
91 // to the outside world.
94 // PageTrace enables GODEBUG=pagetrace=/path/to/result. This feature
95 // is a GOEXPERIMENT due to a security risk with setuid binaries:
96 // this compels the Go runtime to write to some arbitrary file, which
100 // CgoCheck2 enables an expensive cgo rule checker.
101 // When this experiment is enabled, cgo rule checks occur regardless
102 // of the GODEBUG=cgocheck setting provided at runtime.
105 // LoopVar changes loop semantics so that each iteration gets its own
106 // copy of the iteration variable.
109 // CacheProg adds support to cmd/go to use a child process to implement
110 // the build cache; see https://github.com/golang/go/issues/59719.
113 // NewInliner enables a new+improved version of the function
114 // inlining phase within the Go compiler.
117 // Range enables range over int and func.