ucfg.goversion = set(ucfg.GoVersion)
	ucfg.program = make(map[string]bool, len(ucfg.Programs))
	ucfg.pgversion = make(map[pgkey]bool, len(ucfg.Programs))
	ucfg.pgcounter = make(map[pgkey]bool, len(ucfg.Programs))
	ucfg.pgcounterprefix = make(map[pgkey]bool, len(ucfg.Programs))
	ucfg.pgstack = make(map[pgkey]bool, len(ucfg.Programs))
	ucfg.rate = make(map[pgkey]float64)
	for _, p := range ucfg.Programs {
		ucfg.program[p.Name] = true

delivered to the Notify channel, and the write will fail with an EPIPE
error.

This means that, by default, command line programs will behave like
typical Unix command line programs, while other programs will not
crash with SIGPIPE when writing to a closed network connection.

# Go programs that use cgo or SWIG

In a Go program that includes non-Go code, typically C/C++ code
accessed using cgo or SWIG, Go's startup code normally runs first. It

// It guarantees to make a copy of s into a new allocation,
// which can be important when retaining only a small substring
// of a much larger string. Using Clone can help such programs
// use less memory. Of course, since using Clone makes a copy,
// overuse of Clone can make programs use more memory.
// Clone should typically be used only rarely, and only when
// profiling indicates that it is needed.

variable.
Test names are defined as the name of the `.go` file that generates the
trace, but with the `.go` extension removed.

## Trace test programs

The trace test programs in the `testprog` directory generate traces to
stdout.
Otherwise they're just normal programs.

## Trace debug commands

The `cmd` directory contains helpful tools for debugging traces.

* `gotraceraw` parses traces without validation.

## Notable Packages

- The [x/telemetry/counter](https://pkg.go.dev/golang.org/x/telemetry/counter)
  package provides a library for instrumenting programs with counters and stack
  reports.
- The [x/telemetry/upload](https://pkg.go.dev/golang.org/x/telemetry/upload)
  package provides a hook for Go toolchain programs to upload telemetry data,
  if the user has opted in to telemetry uploading.

<p>
The Go memory model restricts compiler optimizations as much as it does Go programs.
Some compiler optimizations that would be valid in single-threaded programs are not valid in all Go programs.
In particular, a compiler must not introduce writes that do not exist in the original program,
it must not allow a single read to observe multiple values,
and it must not allow a single write to write multiple values.

		}
		for _, p := range report.Programs {
			// does the uploadConfig want this program?
			// if so, copy over the Stacks and Counters
			// that the uploadConfig mentions.
			if !cfg.HasGoVersion(p.GoVersion) || !cfg.HasProgram(p.Program) || !cfg.HasVersion(p.Program, p.Version) {
				continue
			}
			x := &telemetry.ProgramReport{
				Program:   p.Program,
				Version:   p.Version,
				GOOS:      p.GOOS,

type UploadConfig struct {
	GOOS       []string
	GOARCH     []string
	GoVersion  []string
	SampleRate float64
	Programs   []*ProgramConfig
}

type ProgramConfig struct {
	// the counter names may have to be
	// repeated for each program. (e.g., if the counters are in a package
	// that is used in more than one program.)
	Name     string
	Versions []string        // versions present in a counterconfig

now returns 0 instead of 1, which may affect programs that
poll the length to decide whether a receive on the timer channel
will succeed.
Such code should use a non-blocking receive instead.

These new behaviors are only enabled when the main Go program
is in a module with a `go.mod` `go` line using Go 1.23.0 or later.
When Go 1.23 builds older programs, the old behaviors remain in effect.

stderr 'panic: panic called with nil argument'

! go run rsc.io/panicnil
stderr 'panic: panic called with nil argument'

# Programs in Go 1.20 work module use old panic nil behavior.
cp go.mod.20 go.mod
! go run .
stderr 'panic: nil'

! go run rsc.io/panicnil
stderr 'panic: nil'

# Programs in no module at all should use their go.mod file.
rm go.mod
! go run rsc.io/panicnil@v1.0.0
stderr 'panic: nil'

rm go.mod