A linker command line flag `-checklinkname=0` can be used to disable
this check, for debugging and experimenting purposes.

<!-- CL 473495 -->
When building a dynamically linked ELF binary (including PIE binary), the

	extname     map[Sym]string      // stores Extname symbol attribute
	elfType     map[Sym]elf.SymType // stores elf type symbol property
	elfSym      map[Sym]int32       // stores elf sym symbol property
	localElfSym map[Sym]int32       // stores "local" elf sym symbol property
	symPkg      map[Sym]string      // stores package for symbol, or library for shlib-derived syms

	case objabi.ElfRelocOffset + objabi.RelocType(elf.R_AARCH64_CALL26),
		objabi.ElfRelocOffset + objabi.RelocType(elf.R_AARCH64_JUMP26),
		objabi.MachoRelocOffset + MACHO_ARM64_RELOC_BRANCH26*2 + pcrel:
		return true

	// ARM
	case objabi.ElfRelocOffset + objabi.RelocType(elf.R_ARM_CALL),
		objabi.ElfRelocOffset + objabi.RelocType(elf.R_ARM_PC24),
		objabi.ElfRelocOffset + objabi.RelocType(elf.R_ARM_JUMP24):
		return true
	}

they need to be linked into the final binary, along with the libraries
they might depend on (in the case of puts, stdio). cmd/link has been
extended to understand basic ELF files, but it does not understand ELF
in the full complexity that modern C libraries embrace, so it cannot
in general generate direct references to the system libraries.

Instead, the build process generates an object file using dynamic

		sym, err := f.file.Symbols()
		if err != nil {
			return nil, err
		}
		f.sym = sym
	}
	var out []*driver.Sym
	for _, s := range f.sym {
		// Ignore a symbol with address 0 and size 0.
		// An ELF STT_FILE symbol will look like that.
		if s.Addr == 0 && s.Size == 0 {
			continue
		}
		if (r == nil || r.MatchString(s.Name)) && (addr == 0 || s.Addr <= addr && addr < s.Addr+uint64(s.Size)) {

	# suffix array
	encoding/binary, regexp
	< index/suffixarray;

	# executable parsing
	FMT, encoding/binary, compress/zlib, internal/saferio, internal/zstd, sort
	< runtime/debug
	< debug/dwarf
	< debug/elf, debug/gosym, debug/macho, debug/pe, debug/plan9obj, internal/xcoff
	< debug/buildinfo
	< DEBUG;

	# go parser and friends.
	FMT, sort
	< internal/gover
	< go/version
	< go/token
	< go/scanner

// a function pointer) as R2 may not be preserved when calling this
// function. In those cases, the caller preserves their R2.
TEXT runtime·sigtramp(SB),NOSPLIT|NOFRAME,$0
#endif
	// This is called with ELF calling conventions. Convert to Go.
	// Allocate space for argument storage to call runtime.sigtrampgo.
	STACK_AND_SAVE_HOST_TO_GO_ABI(32)

	// this might be called in external code context,
	// where g is not set.

	}
	args = append(args, "-o", obj, src)
	tg.run(args...)

	switch runtime.GOOS {
	case "linux", "android", "freebsd":
		f, err := elf.Open(obj)
		if err != nil {
			t.Fatal(err)
		}
		defer f.Close()
		if f.Type != elf.ET_DYN {
			t.Errorf("PIE type must be ET_DYN, but %s", f.Type)
		}
	case "darwin", "ios":
		f, err := macho.Open(obj)
		if err != nil {
			t.Fatal(err)

		return err == nil && strings.Contains(string(out), "GNU")
	} else {
		return false
	}
}

// gccgoBuildIDFile creates an assembler file that records the
// action's build ID in an SHF_EXCLUDE section for ELF files or
// in a CSECT in XCOFF files.
func (b *Builder) gccgoBuildIDFile(a *Action) (string, error) {
	sfile := a.Objdir + "_buildid.s"

	var buf bytes.Buffer
	if cfg.Goos == "aix" {

// license that can be found in the LICENSE file.

// Annotate Ref in Prog with C types by parsing gcc debug output.
// Conversion of debug output to Go types.

package main

import (
	"bytes"
	"debug/dwarf"
	"debug/elf"
	"debug/macho"
	"debug/pe"
	"encoding/binary"
	"errors"
	"flag"
	"fmt"
	"go/ast"
	"go/parser"
	"go/token"
	"internal/xcoff"
	"math"
	"os"
	"os/exec"
	"strconv"
	"strings"
	"unicode"