// standard error and fails, logging msg, if it is found.
func (tg *testgoData) grepStderrNot(match, msg string) {
	tg.t.Helper()
	tg.doGrepNot(match, &tg.stderr, "error", msg)
}

// grepBothNot looks for a regular expression in the test run's
// standard output or standard error and fails, logging msg, if it is
// found.
func (tg *testgoData) grepBothNot(match, msg string) {
	tg.t.Helper()

	// VendorModulesInGOROOTSrc indicates that if we are within a module in
	// GOROOT/src, packages in the module's vendor directory should be resolved as
	// actual module dependencies (instead of standard-library packages).
	VendorModulesInGOROOTSrc bool

	// ResolveMissingImports indicates that we should attempt to add module
	// dependencies as needed to resolve imports of packages that are not found.
	//

To disable the running of go vet, use the -vet=off flag. To run all
checks, use the -vet=all flag.

All test output and summary lines are printed to the go command's
standard output, even if the test printed them to its own standard
error. (The go command's standard error is reserved for printing
errors building the tests.)

The go command places $GOROOT/bin at the beginning of $PATH
in the test's environment, so that tests that execute

	// We used to use it for C objects.
	// Now we use it for the build cache, to separate dist's cache
	// from any other cache the user might have, and for the location
	// to build the bootstrap versions of the standard library.
	obj := pathf("%s/pkg/obj", goroot)
	if !isdir(obj) {
		xmkdir(obj)
	}
	xatexit(func() { xremove(obj) })

	// Create build cache directory.
	objGobuild := pathf("%s/pkg/obj/go-build", goroot)

	modRoot map[module.Version]string

	// pathPrefix is the path prefix for packages in the module, without a trailing
	// slash. For most modules, pathPrefix is just version.Path, but the
	// standard-library module "std" has an empty prefix.
	pathPrefix map[module.Version]string

	// inGorootSrc caches whether modRoot is within GOROOT/src.
	// The "std" module is special within GOROOT/src, but not otherwise.

}

// runGcc runs the gcc command line args with stdin on standard input.
// If the command exits with a non-zero exit status, runGcc prints
// details about what was run and exits.
// Otherwise runGcc returns the data written to standard output and standard error.
// Note that for some of the uses we expect useful data back
// on standard error, but for those uses gcc must still exit 0.

			if len(packages) > 0 {
				if q.rawVersion != "" {
					return errSet(fmt.Errorf("can't request explicit version %q of standard library package %s", q.version, q.pattern))
				}

				q.matchesPackages = true
				return pathSet{} // No module needed for standard library.
			}
		}

		pkgMods, mod, err := r.queryPattern(ctx, q.pattern, q.version, r.initialSelected)
		if err != nil {

			// already using the result of a clean build, and because of test sharding
			// and virtualization we usually start with a clean GOCACHE, so we would
			// end up rebuilding large parts of the standard library that aren't
			// otherwise relevant to the actual set of packages under test.
			goInstall(toolenv(), gorootBinGo, toolchain...)
			goInstall(toolenv(), gorootBinGo, toolchain...)

// linker, which will create its own dynamic symbol tables. For
// internal linking, this may turn weak imports into strong imports,
// which could cause dynamic linking to fail if a symbol really isn't
// defined. However, the standard library depends on everything it
// imports, and this is the primary use of dynamic symbol tables with
// internal linking.
func elfImportedSymbols(f *elf.File) []elf.ImportedSymbol {
	syms, _ := f.DynamicSymbols()