cmd/link: fix testdata generation

Fixes #8494.

LGTM=rsc
R=golang-codereviews, gobot, rsc, evankroske
CC=golang-codereviews
https://golang.org/cl/123040043

src/cmd/link/pclntab_test.go

@@ -276,6 +276,12 @@ func checkPCData(t *testing.T, r *SymReader, name string, off, pc, pnum, val int
 // readPCData reads the PCData table offset off
 // to obtain and return the value associated with pc.
 func readPCData(t *testing.T, r *SymReader, name, pcdataname string, pcoff uint32, pc int) (int, bool) {
+	// "If pcsp, pcfile, pcln, or any of the pcdata offsets is zero,
+	// that table is considered missing, and all PCs take value -1."
+	if pcoff == 0 {
+		return -1, true
+	}
+
 	var it PCIter
 	for it.Init(r.p, r.data[pcoff:]); !it.Done; it.Next() {
 		if it.PC <= uint32(pc) && uint32(pc) < it.NextPC {

src/cmd/link/testdata/Makefile

@@ -9,7 +9,7 @@ ALL=\
 all: $(ALL)
 
 %.6: %.s
-	go tool 6a $*.s
+	GOARCH=amd64 GOOS=darwin go tool 6a -trimpath=$(shell pwd) $*.s
 
 pclntab.s: genpcln.go
 	go run genpcln.go >pclntab.s

src/cmd/link/testdata/link.hello.darwin.amd64

@@ -6,8 +6,8 @@
 *
 00000060  00 00 00 00 00 00 00 00  19 00 00 00 38 01 00 00  |............8...|
 00000070  5f 5f 54 45 58 54 00 00  00 00 00 00 00 00 00 00  |__TEXT..........|
-00000080  00 10 00 00 00 00 00 00  d6 10 00 00 00 00 00 00  |................|
-00000090  00 00 00 00 00 00 00 00  d6 10 00 00 00 00 00 00  |................|
+00000080  00 10 00 00 00 00 00 00  b0 10 00 00 00 00 00 00  |................|
+00000090  00 00 00 00 00 00 00 00  b0 10 00 00 00 00 00 00  |................|
 000000a0  07 00 00 00 05 00 00 00  03 00 00 00 00 00 00 00  |................|
 000000b0  5f 5f 74 65 78 74 00 00  00 00 00 00 00 00 00 00  |__text..........|
 000000c0  5f 5f 54 45 58 54 00 00  00 00 00 00 00 00 00 00  |__TEXT..........|
@@ -21,7 +21,7 @@
 *
 00000150  5f 5f 66 75 6e 63 74 61  62 00 00 00 00 00 00 00  |__functab.......|
 00000160  5f 5f 54 45 58 54 00 00  00 00 00 00 00 00 00 00  |__TEXT..........|
-00000170  20 20 00 00 00 00 00 00  b6 00 00 00 00 00 00 00  |  ..............|
+00000170  20 20 00 00 00 00 00 00  90 00 00 00 00 00 00 00  |  ..............|
 00000180  20 10 00 00 00 00 00 00  00 00 00 00 00 00 00 00  | ...............|
 *
 000001a0  19 00 00 00 98 00 00 00  5f 5f 44 41 54 41 00 00  |........__DATA..|
@@ -48,10 +48,7 @@
 00001070  00 00 00 00 00 00 00 00  5f 72 74 30 5f 67 6f 00  |........_rt0_go.|
 00001080  02 20 00 04 20 00 06 05  02 05 02 05 02 05 02 02  |. .. ...........|
 00001090  02 02 02 05 02 02 02 01  00 00 00 00 00 00 00 00  |................|
-000010a0  02 00 00 00 88 00 00 00  2f 55 73 65 72 73 2f 72  |......../Users/r|
-000010b0  73 63 2f 67 2f 67 6f 2f  73 72 63 2f 63 6d 64 2f  |sc/g/go/src/cmd/|
-000010c0  6c 69 6e 6b 2f 74 65 73  74 64 61 74 61 2f 68 65  |link/testdata/he|
-000010d0  6c 6c 6f 2e 73 00 00 00  00 00 00 00 00 00 00 00  |llo.s...........|
+000010a0  02 00 00 00 88 00 00 00  68 65 6c 6c 6f 2e 73 00  |........hello.s.|
 *
 00002000  68 65 6c 6c 6f 20 77 6f  72 6c 64 0a              |hello world.|
 0000200c