}
		pcs := make([]uintptr, 20)
		n := runtime.Callers(1, pcs)
		for _, pc := range pcs[:n] {
			if runtime.FuncForPC(pc).Name() == "main.main" {
				return
			}
		}
		panic("cannot find main.main in backtrace")
	}()

	prep()
	f() // should panic
}

func funcPC(f interface{}) uintptr {
	var ptr uintptr
	return **(**uintptr)(unsafe.Pointer(uintptr(unsafe.Pointer(&f)) + unsafe.Sizeof(ptr)))
}

// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

package pkgbits

import (
	"fmt"
	"runtime"
	"strings"
)

// fmtFrames formats a backtrace for reporting reader/writer desyncs.
func fmtFrames(pcs ...uintptr) []string {
	res := make([]string, 0, len(pcs))
	walkFrames(pcs, func(file string, line int, name string, offset uintptr) {

			// .. element: remove to last /
			r += 2
			switch {
			case out.w > dotdot:
				// can backtrack
				out.w--
				for out.w > dotdot && out.index(out.w) != '/' {
					out.w--
				}
			case !rooted:
				// cannot backtrack, but not rooted, so append .. element.
				if out.w > 0 {
					out.append('/')
				}
				out.append('.')
				out.append('.')

// skipframes is the number of frames to omit during tracing, counting from
// runtime_SemacquireMutex's caller.
// The different forms of this function just tell the runtime how to present
// the reason for waiting in a backtrace, and is used to compute some metrics.
// Otherwise they're functionally identical.
func runtime_SemacquireMutex(s *uint32, lifo bool, skipframes int)
func runtime_SemacquireRWMutexR(s *uint32, lifo bool, skipframes int)

			// .. element: remove to last separator
			r += 2
			switch {
			case out.w > dotdot:
				// can backtrack
				out.w--
				for out.w > dotdot && !IsPathSeparator(out.index(out.w)) {
					out.w--
				}
			case !rooted:
				// cannot backtrack, but not rooted, so append .. element.
				if out.w > 0 {
					out.append(Separator)
				}
				out.append('.')
				out.append('.')

// generations moving forward. Prefer traceEventWriter.stack.
func traceStack(skip int, gp *g, gen uintptr) uint64 {
	var pcBuf [traceStackSize]uintptr

	// Figure out gp and mp for the backtrace.
	var mp *m
	if gp == nil {
		mp = getg().m
		gp = mp.curg
	}

	// Double-check that we own the stack we're about to trace.
	if debug.traceCheckStackOwnership != 0 && gp != nil {
		status := readgstatus(gp)

  // true of the mapping has changed.
  bool PropagateInputToOutput(const Value& operand, const OpResult& result);

  // Analyzes while loops to compute resource IDs for the loop results.
  // `body_info` is the backtrack analysis info for the loop body.
  void AnalyzeWhileLoop(Operation* while_op,
                        const BacktrackAnalysisInfo& body_info);

  // Analyzes tf.Case/tf.If ops to compute resource IDs.

	re(`-f(no-)?fast-math`),
	re(`-f(no-)?inline-functions`),
	re(`-finput-charset=([^@\-].*)`),
	re(`-f(no-)?fat-lto-objects`),
	re(`-f(no-)?keep-inline-dllexport`),
	re(`-f(no-)?lto`),
	re(`-fmacro-backtrace-limit=(.+)`),
	re(`-fmessage-length=(.+)`),
	re(`-f(no-)?modules`),
	re(`-f(no-)?objc-arc`),
	re(`-f(no-)?objc-nonfragile-abi`),
	re(`-f(no-)?objc-legacy-dispatch`),
	re(`-f(no-)?omit-frame-pointer`),

// in the caller's stack frame. These stubs write the args into that stack space and
// then tail call to the corresponding runtime handler.
// The tail call makes these stubs disappear in backtraces.
TEXT runtime·panicIndex<ABIInternal>(SB),NOSPLIT,$0-16
	JMP	runtime·goPanicIndex<ABIInternal>(SB)
TEXT runtime·panicIndexU<ABIInternal>(SB),NOSPLIT,$0-16
	JMP	runtime·goPanicIndexU<ABIInternal>(SB)

				return err
			}
			return nil
		}()
	})
	return compiler.version, compiler.err
}

// compilerSupportsLocation reports whether the compiler should be
// able to provide file/line information in backtraces.
func compilerSupportsLocation() bool {
	compiler, err := compilerVersion()
	if err != nil {
		return false
	}
	switch compiler.name {
	case "gcc":
		return compiler.major >= 10
	case "clang":