code can only be used as a dynamic library). On the other hand, when
using internal linking, cmd/link can generate Go binaries by itself.

In order to allow linking arbitrary object files without requiring
dynamic libraries, cgo supports an "external" linking mode too. In
external linking mode, cmd/link does not process any host object files.
Instead, it collects all the Go code and writes a single go.o object

accept arbitrary argument types, but printing of boolean, numeric, and string
<a href="#Types">types</a> must be supported.
</p>

<h2 id="Packages">Packages</h2>

<p>
Go programs are constructed by linking together <i>packages</i>.
A package in turn is constructed from one or more source files
that together declare constants, types, variables and functions
belonging to the package and which are accessible in all files

import "testing"

// If gcc is used, and linking internally, __mulsc3 and __muldc3
// will be linked in from libgcc which make several R_PPC64_TOC16_DS
// relocations which may not be resolvable with the internal linker.
func test8694(t *testing.T) { t.Skip("not supported on ppc64/ppc64le with internal linking") }

accept arbitrary argument types, but printing of boolean, numeric, and string
<a href="#Types">types</a> must be supported.
</p>


<h2 id="Packages">Packages</h2>

<p>
Go programs are constructed by linking together <i>packages</i>.
A package in turn is constructed from one or more source files
that together declare constants, types, variables and functions
belonging to the package and which are accessible in all files

</pre>

<p>
The <code>FUNCDATA</code> and <code>PCDATA</code> directives contain information
for use by the garbage collector; they are introduced by the compiler.
</p>

<p>
To see what gets put in the binary after linking, use <code>go tool objdump</code>:
</p>

<pre>
$ go build -o x.exe x.go
$ go tool objdump -s main.main x.exe
TEXT main.main(SB) /tmp/x.go
  x.go:3		0x10501c0		65488b0c2530000000	MOVQ GS:0x30, CX

	}

	// 2. Shrink
	minRune := func(r rune) rune { return 'a' }
	m = Map(minRune, []byte(tenRunes(unicode.MaxRune)))
	expect = a
	if string(m) != expect {
		t.Errorf("shrinking: expected %q got %q", expect, m)
	}

	// 3. Rot13
	m = Map(rot13, []byte("a to zed"))
	expect = "n gb mrq"
	if string(m) != expect {
		t.Errorf("rot13: expected %q got %q", expect, m)
	}

	MOVQ R15, AX // ERROR "when dynamic linking, R15 is clobbered by a global variable access and is used here"
	RET
TEXT ·a8(SB), 0, $0-0
	CMPL runtime·writeBarrier(SB), $0
	ADDQ AX, R15 // ERROR "when dynamic linking, R15 is clobbered by a global variable access and is used here"
	RET
TEXT ·a9(SB), 0, $0-0
	CMPL runtime·writeBarrier(SB), $0

  owners should update their assembly code to avoid the alignment assumption, as this
  workaround will be removed in a future release.
</p>

<p><!-- CL 525475 -->
  On the <code>windows/amd64 port</code>, programs linking or loading Go libraries built with
  <code>-buildmode=c-archive</code> or <code>-buildmode=c-shared</code> can now use
  the <code>SetUnhandledExceptionFilter</code> Win32 function to catch exceptions not handled