libgo/misc/cgo/errors/ptr_test.go

   1 // Copyright 2015 The Go Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style
   3 // license that can be found in the LICENSE file.
   4
   5 // Tests that cgo detects invalid pointer passing at runtime.
   6
   7 package errorstest
   8
   9 import (
  10         "bytes"
  11         "flag"
  12         "fmt"
  13         "os"
  14         "os/exec"
  15         "path/filepath"
  16         "strings"
  17         "sync/atomic"
  18         "testing"
  19 )
  20
  21 var tmp = flag.String("tmp", "", "use `dir` for temporary files and do not clean up")
  22
  23 // ptrTest is the tests without the boilerplate.
  24 type ptrTest struct {
  25         name      string   // for reporting
  26         c         string   // the cgo comment
  27         c1        string   // cgo comment forced into non-export cgo file
  28         imports   []string // a list of imports
  29         support   string   // supporting functions
  30         body      string   // the body of the main function
  31         extra     []extra  // extra files
  32         fail      bool     // whether the test should fail
  33         expensive bool     // whether the test requires the expensive check
  34 }
  35
  36 type extra struct {
  37         name     string
  38         contents string
  39 }
  40
  41 var ptrTests = []ptrTest{
  42         {
  43                 // Passing a pointer to a struct that contains a Go pointer.
  44                 name: "ptr1",
  45                 c:    `typedef struct s1 { int *p; } s1; void f1(s1 *ps) {}`,
  46                 body: `C.f1(&C.s1{new(C.int)})`,
  47                 fail: true,
  48         },
  49         {
  50                 // Passing a pointer to a struct that contains a Go pointer.
  51                 name: "ptr2",
  52                 c:    `typedef struct s2 { int *p; } s2; void f2(s2 *ps) {}`,
  53                 body: `p := &C.s2{new(C.int)}; C.f2(p)`,
  54                 fail: true,
  55         },
  56         {
  57                 // Passing a pointer to an int field of a Go struct
  58                 // that (irrelevantly) contains a Go pointer.
  59                 name: "ok1",
  60                 c:    `struct s3 { int i; int *p; }; void f3(int *p) {}`,
  61                 body: `p := &C.struct_s3{i: 0, p: new(C.int)}; C.f3(&p.i)`,
  62                 fail: false,
  63         },
  64         {
  65                 // Passing a pointer to a pointer field of a Go struct.
  66                 name: "ptrfield",
  67                 c:    `struct s4 { int i; int *p; }; void f4(int **p) {}`,
  68                 body: `p := &C.struct_s4{i: 0, p: new(C.int)}; C.f4(&p.p)`,
  69                 fail: true,
  70         },
  71         {
  72                 // Passing a pointer to a pointer field of a Go
  73                 // struct, where the field does not contain a Go
  74                 // pointer, but another field (irrelevantly) does.
  75                 name: "ptrfieldok",
  76                 c:    `struct s5 { int *p1; int *p2; }; void f5(int **p) {}`,
  77                 body: `p := &C.struct_s5{p1: nil, p2: new(C.int)}; C.f5(&p.p1)`,
  78                 fail: false,
  79         },
  80         {
  81                 // Passing the address of a slice with no Go pointers.
  82                 name:    "sliceok1",
  83                 c:       `void f6(void **p) {}`,
  84                 imports: []string{"unsafe"},
  85                 body:    `s := []unsafe.Pointer{nil}; C.f6(&s[0])`,
  86                 fail:    false,
  87         },
  88         {
  89                 // Passing the address of a slice with a Go pointer.
  90                 name:    "sliceptr1",
  91                 c:       `void f7(void **p) {}`,
  92                 imports: []string{"unsafe"},
  93                 body:    `i := 0; s := []unsafe.Pointer{unsafe.Pointer(&i)}; C.f7(&s[0])`,
  94                 fail:    true,
  95         },
  96         {
  97                 // Passing the address of a slice with a Go pointer,
  98                 // where we are passing the address of an element that
  99                 // is not a Go pointer.
 100                 name:    "sliceptr2",
 101                 c:       `void f8(void **p) {}`,
 102                 imports: []string{"unsafe"},
 103                 body:    `i := 0; s := []unsafe.Pointer{nil, unsafe.Pointer(&i)}; C.f8(&s[0])`,
 104                 fail:    true,
 105         },
 106         {
 107                 // Passing the address of a slice that is an element
 108                 // in a struct only looks at the slice.
 109                 name:    "sliceok2",
 110                 c:       `void f9(void **p) {}`,
 111                 imports: []string{"unsafe"},
 112                 support: `type S9 struct { p *int; s []unsafe.Pointer }`,
 113                 body:    `i := 0; p := &S9{p:&i, s:[]unsafe.Pointer{nil}}; C.f9(&p.s[0])`,
 114                 fail:    false,
 115         },
 116         {
 117                 // Passing the address of a slice of an array that is
 118                 // an element in a struct, with a type conversion.
 119                 name:    "sliceok3",
 120                 c:       `void f10(void* p) {}`,
 121                 imports: []string{"unsafe"},
 122                 support: `type S10 struct { p *int; a [4]byte }`,
 123                 body:    `i := 0; p := &S10{p:&i}; s := p.a[:]; C.f10(unsafe.Pointer(&s[0]))`,
 124                 fail:    false,
 125         },
 126         {
 127                 // Passing the address of a slice of an array that is
 128                 // an element in a struct, with a type conversion.
 129                 name:    "sliceok4",
 130                 c:       `typedef void* PV11; void f11(PV11 p) {}`,
 131                 imports: []string{"unsafe"},
 132                 support: `type S11 struct { p *int; a [4]byte }`,
 133                 body:    `i := 0; p := &S11{p:&i}; C.f11(C.PV11(unsafe.Pointer(&p.a[0])))`,
 134                 fail:    false,
 135         },
 136         {
 137                 // Passing the address of a static variable with no
 138                 // pointers doesn't matter.
 139                 name:    "varok",
 140                 c:       `void f12(char** parg) {}`,
 141                 support: `var hello12 = [...]C.char{'h', 'e', 'l', 'l', 'o'}`,
 142                 body:    `parg := [1]*C.char{&hello12[0]}; C.f12(&parg[0])`,
 143                 fail:    false,
 144         },
 145         {
 146                 // Passing the address of a static variable with
 147                 // pointers does matter.
 148                 name:    "var1",
 149                 c:       `void f13(char*** parg) {}`,
 150                 support: `var hello13 = [...]*C.char{new(C.char)}`,
 151                 body:    `parg := [1]**C.char{&hello13[0]}; C.f13(&parg[0])`,
 152                 fail:    true,
 153         },
 154         {
 155                 // Storing a Go pointer into C memory should fail.
 156                 name: "barrier",
 157                 c: `#include <stdlib.h>
 158                     char **f14a() { return malloc(sizeof(char*)); }
 159                     void f14b(char **p) {}`,
 160                 body:      `p := C.f14a(); *p = new(C.char); C.f14b(p)`,
 161                 fail:      true,
 162                 expensive: true,
 163         },
 164         {
 165                 // Storing a Go pointer into C memory by assigning a
 166                 // large value should fail.
 167                 name: "barrierstruct",
 168                 c: `#include <stdlib.h>
 169                     struct s15 { char *a[10]; };
 170                     struct s15 *f15() { return malloc(sizeof(struct s15)); }
 171                     void f15b(struct s15 *p) {}`,
 172                 body:      `p := C.f15(); p.a = [10]*C.char{new(C.char)}; C.f15b(p)`,
 173                 fail:      true,
 174                 expensive: true,
 175         },
 176         {
 177                 // Storing a Go pointer into C memory using a slice
 178                 // copy should fail.
 179                 name: "barrierslice",
 180                 c: `#include <stdlib.h>
 181                     struct s16 { char *a[10]; };
 182                     struct s16 *f16() { return malloc(sizeof(struct s16)); }
 183                     void f16b(struct s16 *p) {}`,
 184                 body:      `p := C.f16(); copy(p.a[:], []*C.char{new(C.char)}); C.f16b(p)`,
 185                 fail:      true,
 186                 expensive: true,
 187         },
 188         {
 189                 // A very large value uses a GC program, which is a
 190                 // different code path.
 191                 name: "barriergcprogarray",
 192                 c: `#include <stdlib.h>
 193                     struct s17 { char *a[32769]; };
 194                     struct s17 *f17() { return malloc(sizeof(struct s17)); }
 195                     void f17b(struct s17 *p) {}`,
 196                 body:      `p := C.f17(); p.a = [32769]*C.char{new(C.char)}; C.f17b(p)`,
 197                 fail:      true,
 198                 expensive: true,
 199         },
 200         {
 201                 // Similar case, with a source on the heap.
 202                 name: "barriergcprogarrayheap",
 203                 c: `#include <stdlib.h>
 204                     struct s18 { char *a[32769]; };
 205                     struct s18 *f18() { return malloc(sizeof(struct s18)); }
 206                     void f18b(struct s18 *p) {}
 207                     void f18c(void *p) {}`,
 208                 imports:   []string{"unsafe"},
 209                 body:      `p := C.f18(); n := &[32769]*C.char{new(C.char)}; p.a = *n; C.f18b(p); n[0] = nil; C.f18c(unsafe.Pointer(n))`,
 210                 fail:      true,
 211                 expensive: true,
 212         },
 213         {
 214                 // A GC program with a struct.
 215                 name: "barriergcprogstruct",
 216                 c: `#include <stdlib.h>
 217                     struct s19a { char *a[32769]; };
 218                     struct s19b { struct s19a f; };
 219                     struct s19b *f19() { return malloc(sizeof(struct s19b)); }
 220                     void f19b(struct s19b *p) {}`,
 221                 body:      `p := C.f19(); p.f = C.struct_s19a{[32769]*C.char{new(C.char)}}; C.f19b(p)`,
 222                 fail:      true,
 223                 expensive: true,
 224         },
 225         {
 226                 // Similar case, with a source on the heap.
 227                 name: "barriergcprogstructheap",
 228                 c: `#include <stdlib.h>
 229                     struct s20a { char *a[32769]; };
 230                     struct s20b { struct s20a f; };
 231                     struct s20b *f20() { return malloc(sizeof(struct s20b)); }
 232                     void f20b(struct s20b *p) {}
 233                     void f20c(void *p) {}`,
 234                 imports:   []string{"unsafe"},
 235                 body:      `p := C.f20(); n := &C.struct_s20a{[32769]*C.char{new(C.char)}}; p.f = *n; C.f20b(p); n.a[0] = nil; C.f20c(unsafe.Pointer(n))`,
 236                 fail:      true,
 237                 expensive: true,
 238         },
 239         {
 240                 // Exported functions may not return Go pointers.
 241                 name: "export1",
 242                 c:    `extern unsigned char *GoFn21();`,
 243                 support: `//export GoFn21
 244                           func GoFn21() *byte { return new(byte) }`,
 245                 body: `C.GoFn21()`,
 246                 fail: true,
 247         },
 248         {
 249                 // Returning a C pointer is fine.
 250                 name: "exportok",
 251                 c: `#include <stdlib.h>
 252                     extern unsigned char *GoFn22();`,
 253                 support: `//export GoFn22
 254                           func GoFn22() *byte { return (*byte)(C.malloc(1)) }`,
 255                 body: `C.GoFn22()`,
 256         },
 257         {
 258                 // Passing a Go string is fine.
 259                 name: "passstring",
 260                 c: `#include <stddef.h>
 261                     typedef struct { const char *p; ptrdiff_t n; } gostring23;
 262                     gostring23 f23(gostring23 s) { return s; }`,
 263                 imports: []string{"unsafe"},
 264                 body:    `s := "a"; r := C.f23(*(*C.gostring23)(unsafe.Pointer(&s))); if *(*string)(unsafe.Pointer(&r)) != s { panic(r) }`,
 265         },
 266         {
 267                 // Passing a slice of Go strings fails.
 268                 name:    "passstringslice",
 269                 c:       `void f24(void *p) {}`,
 270                 imports: []string{"strings", "unsafe"},
 271                 support: `type S24 struct { a [1]string }`,
 272                 body:    `s := S24{a:[1]string{strings.Repeat("a", 2)}}; C.f24(unsafe.Pointer(&s.a[0]))`,
 273                 fail:    true,
 274         },
 275         {
 276                 // Exported functions may not return strings.
 277                 name:    "retstring",
 278                 c:       `extern void f25();`,
 279                 imports: []string{"strings"},
 280                 support: `//export GoStr25
 281                           func GoStr25() string { return strings.Repeat("a", 2) }`,
 282                 body: `C.f25()`,
 283                 c1: `#include <stddef.h>
 284                      typedef struct { const char *p; ptrdiff_t n; } gostring25;
 285                      extern gostring25 GoStr25();
 286                      void f25() { GoStr25(); }`,
 287                 fail: true,
 288         },
 289         {
 290                 // Don't check non-pointer data.
 291                 // Uses unsafe code to get a pointer we shouldn't check.
 292                 // Although we use unsafe, the uintptr represents an integer
 293                 // that happens to have the same representation as a pointer;
 294                 // that is, we are testing something that is not unsafe.
 295                 name: "ptrdata1",
 296                 c: `#include <stdlib.h>
 297                     void f26(void* p) {}`,
 298                 imports: []string{"unsafe"},
 299                 support: `type S26 struct { p *int; a [8*8]byte; u uintptr }`,
 300                 body:    `i := 0; p := &S26{u:uintptr(unsafe.Pointer(&i))}; q := (*S26)(C.malloc(C.size_t(unsafe.Sizeof(*p)))); *q = *p; C.f26(unsafe.Pointer(q))`,
 301                 fail:    false,
 302         },
 303         {
 304                 // Like ptrdata1, but with a type that uses a GC program.
 305                 name: "ptrdata2",
 306                 c: `#include <stdlib.h>
 307                     void f27(void* p) {}`,
 308                 imports: []string{"unsafe"},
 309                 support: `type S27 struct { p *int; a [32769*8]byte; q *int; u uintptr }`,
 310                 body:    `i := 0; p := S27{u:uintptr(unsafe.Pointer(&i))}; q := (*S27)(C.malloc(C.size_t(unsafe.Sizeof(p)))); *q = p; C.f27(unsafe.Pointer(q))`,
 311                 fail:    false,
 312         },
 313         {
 314                 // Check deferred pointers when they are used, not
 315                 // when the defer statement is run.
 316                 name: "defer1",
 317                 c:    `typedef struct s28 { int *p; } s28; void f28(s28 *ps) {}`,
 318                 body: `p := &C.s28{}; defer C.f28(p); p.p = new(C.int)`,
 319                 fail: true,
 320         },
 321         {
 322                 // Check a pointer to a union if the union has any
 323                 // pointer fields.
 324                 name:    "union1",
 325                 c:       `typedef union { char **p; unsigned long i; } u29; void f29(u29 *pu) {}`,
 326                 imports: []string{"unsafe"},
 327                 body:    `var b C.char; p := &b; C.f29((*C.u29)(unsafe.Pointer(&p)))`,
 328                 fail:    true,
 329         },
 330         {
 331                 // Don't check a pointer to a union if the union does
 332                 // not have any pointer fields.
 333                 // Like ptrdata1 above, the uintptr represents an
 334                 // integer that happens to have the same
 335                 // representation as a pointer.
 336                 name:    "union2",
 337                 c:       `typedef union { unsigned long i; } u39; void f39(u39 *pu) {}`,
 338                 imports: []string{"unsafe"},
 339                 body:    `var b C.char; p := &b; C.f39((*C.u39)(unsafe.Pointer(&p)))`,
 340                 fail:    false,
 341         },
 342         {
 343                 // Test preemption while entering a cgo call. Issue #21306.
 344                 name:    "preemptduringcall",
 345                 c:       `void f30() {}`,
 346                 imports: []string{"runtime", "sync"},
 347                 body:    `var wg sync.WaitGroup; wg.Add(100); for i := 0; i < 100; i++ { go func(i int) { for j := 0; j < 100; j++ { C.f30(); runtime.GOMAXPROCS(i) }; wg.Done() }(i) }; wg.Wait()`,
 348                 fail:    false,
 349         },
 350         {
 351                 // Test poller deadline with cgocheck=2.  Issue #23435.
 352                 name:    "deadline",
 353                 c:       `#define US31 10`,
 354                 imports: []string{"os", "time"},
 355                 body:    `r, _, _ := os.Pipe(); r.SetDeadline(time.Now().Add(C.US31 * time.Microsecond))`,
 356                 fail:    false,
 357         },
 358         {
 359                 // Test for double evaluation of channel receive.
 360                 name:    "chanrecv",
 361                 c:       `void f32(char** p) {}`,
 362                 imports: []string{"time"},
 363                 body:    `c := make(chan []*C.char, 2); c <- make([]*C.char, 1); go func() { time.Sleep(10 * time.Second); panic("received twice from chan") }(); C.f32(&(<-c)[0]);`,
 364                 fail:    false,
 365         },
 366         {
 367                 // Test that converting the address of a struct field
 368                 // to unsafe.Pointer still just checks that field.
 369                 // Issue #25941.
 370                 name:    "structfield",
 371                 c:       `void f33(void* p) {}`,
 372                 imports: []string{"unsafe"},
 373                 support: `type S33 struct { p *int; a [8]byte; u uintptr }`,
 374                 body:    `s := &S33{p: new(int)}; C.f33(unsafe.Pointer(&s.a))`,
 375                 fail:    false,
 376         },
 377         {
 378                 // Test that converting multiple struct field
 379                 // addresses to unsafe.Pointer still just checks those
 380                 // fields. Issue #25941.
 381                 name:    "structfield2",
 382                 c:       `void f34(void* p, int r, void* s) {}`,
 383                 imports: []string{"unsafe"},
 384                 support: `type S34 struct { a [8]byte; p *int; b int64; }`,
 385                 body:    `s := &S34{p: new(int)}; C.f34(unsafe.Pointer(&s.a), 32, unsafe.Pointer(&s.b))`,
 386                 fail:    false,
 387         },
 388         {
 389                 // Test that second argument to cgoCheckPointer is
 390                 // evaluated when a deferred function is deferred, not
 391                 // when it is run.
 392                 name:    "defer2",
 393                 c:       `void f35(char **pc) {}`,
 394                 support: `type S35a struct { s []*C.char }; type S35b struct { ps *S35a }`,
 395                 body:    `p := &S35b{&S35a{[]*C.char{nil}}}; defer C.f35(&p.ps.s[0]); p.ps = nil`,
 396                 fail:    false,
 397         },
 398         {
 399                 // Test that indexing into a function call still
 400                 // examines only the slice being indexed.
 401                 name:    "buffer",
 402                 c:       `void f36(void *p) {}`,
 403                 imports: []string{"bytes", "unsafe"},
 404                 body:    `var b bytes.Buffer; b.WriteString("a"); C.f36(unsafe.Pointer(&b.Bytes()[0]))`,
 405                 fail:    false,
 406         },
 407         {
 408                 // Test that bgsweep releasing a finalizer is OK.
 409                 name:    "finalizer",
 410                 c:       `// Nothing to declare.`,
 411                 imports: []string{"os"},
 412                 support: `func open37() { os.Open(os.Args[0]) }; var G37 [][]byte`,
 413                 body:    `for i := 0; i < 10000; i++ { G37 = append(G37, make([]byte, 4096)); if i % 100 == 0 { G37 = nil; open37() } }`,
 414                 fail:    false,
 415         },
 416         {
 417                 // Test that converting generated struct to interface is OK.
 418                 name:    "structof",
 419                 c:       `// Nothing to declare.`,
 420                 imports: []string{"reflect"},
 421                 support: `type MyInt38 int; func (i MyInt38) Get() int { return int(i) }; type Getter38 interface { Get() int }`,
 422                 body:    `t := reflect.StructOf([]reflect.StructField{{Name: "MyInt38", Type: reflect.TypeOf(MyInt38(0)), Anonymous: true}}); v := reflect.New(t).Elem(); v.Interface().(Getter38).Get()`,
 423                 fail:    false,
 424         },
 425         {
 426                 // Test that a converted address of a struct field results
 427                 // in a check for just that field and not the whole struct.
 428                 name:    "structfieldcast",
 429                 c:       `struct S40i { int i; int* p; }; void f40(struct S40i* p) {}`,
 430                 support: `type S40 struct { p *int; a C.struct_S40i }`,
 431                 body:    `s := &S40{p: new(int)}; C.f40((*C.struct_S40i)(&s.a))`,
 432                 fail:    false,
 433         },
 434 }
 435
 436 func TestPointerChecks(t *testing.T) {
 437         dir, exe := buildPtrTests(t)
 438
 439         // We (TestPointerChecks) return before the parallel subtest functions do,
 440         // so we can't just defer os.RemoveAll(dir). Instead we have to wait for
 441         // the parallel subtests to finish. This code looks racy but is not:
 442         // the add +1 run in serial before testOne blocks. The -1 run in parallel
 443         // after testOne finishes.
 444         var pending int32
 445         for _, pt := range ptrTests {
 446                 pt := pt
 447                 t.Run(pt.name, func(t *testing.T) {
 448                         atomic.AddInt32(&pending, +1)
 449                         defer func() {
 450                                 if atomic.AddInt32(&pending, -1) == 0 {
 451                                         os.RemoveAll(dir)
 452                                 }
 453                         }()
 454                         testOne(t, pt, exe)
 455                 })
 456         }
 457 }
 458
 459 func buildPtrTests(t *testing.T) (dir, exe string) {
 460         var gopath string
 461         if *tmp != "" {
 462                 gopath = *tmp
 463                 dir = ""
 464         } else {
 465                 d, err := os.MkdirTemp("", filepath.Base(t.Name()))
 466                 if err != nil {
 467                         t.Fatal(err)
 468                 }
 469                 dir = d
 470                 gopath = d
 471         }
 472
 473         src := filepath.Join(gopath, "src", "ptrtest")
 474         if err := os.MkdirAll(src, 0777); err != nil {
 475                 t.Fatal(err)
 476         }
 477         if err := os.WriteFile(filepath.Join(src, "go.mod"), []byte("module ptrtest"), 0666); err != nil {
 478                 t.Fatal(err)
 479         }
 480
 481         // Prepare two cgo inputs: one for standard cgo and one for //export cgo.
 482         // (The latter cannot have C definitions, only declarations.)
 483         var cgo1, cgo2 bytes.Buffer
 484         fmt.Fprintf(&cgo1, "package main\n\n/*\n")
 485         fmt.Fprintf(&cgo2, "package main\n\n/*\n")
 486
 487         // C code
 488         for _, pt := range ptrTests {
 489                 cgo := &cgo1
 490                 if strings.Contains(pt.support, "//export") {
 491                         cgo = &cgo2
 492                 }
 493                 fmt.Fprintf(cgo, "%s\n", pt.c)
 494                 fmt.Fprintf(&cgo1, "%s\n", pt.c1)
 495         }
 496         fmt.Fprintf(&cgo1, "*/\nimport \"C\"\n\n")
 497         fmt.Fprintf(&cgo2, "*/\nimport \"C\"\n\n")
 498
 499         // Imports
 500         did1 := make(map[string]bool)
 501         did2 := make(map[string]bool)
 502         did1["os"] = true // for ptrTestMain
 503         fmt.Fprintf(&cgo1, "import \"os\"\n")
 504
 505         for _, pt := range ptrTests {
 506                 did := did1
 507                 cgo := &cgo1
 508                 if strings.Contains(pt.support, "//export") {
 509                         did = did2
 510                         cgo = &cgo2
 511                 }
 512                 for _, imp := range pt.imports {
 513                         if !did[imp] {
 514                                 did[imp] = true
 515                                 fmt.Fprintf(cgo, "import %q\n", imp)
 516                         }
 517                 }
 518         }
 519
 520         // Func support and bodies.
 521         for _, pt := range ptrTests {
 522                 cgo := &cgo1
 523                 if strings.Contains(pt.support, "//export") {
 524                         cgo = &cgo2
 525                 }
 526                 fmt.Fprintf(cgo, "%s\nfunc %s() {\n%s\n}\n", pt.support, pt.name, pt.body)
 527         }
 528
 529         // Func list and main dispatch.
 530         fmt.Fprintf(&cgo1, "var funcs = map[string]func() {\n")
 531         for _, pt := range ptrTests {
 532                 fmt.Fprintf(&cgo1, "\t%q: %s,\n", pt.name, pt.name)
 533         }
 534         fmt.Fprintf(&cgo1, "}\n\n")
 535         fmt.Fprintf(&cgo1, "%s\n", ptrTestMain)
 536
 537         if err := os.WriteFile(filepath.Join(src, "cgo1.go"), cgo1.Bytes(), 0666); err != nil {
 538                 t.Fatal(err)
 539         }
 540         if err := os.WriteFile(filepath.Join(src, "cgo2.go"), cgo2.Bytes(), 0666); err != nil {
 541                 t.Fatal(err)
 542         }
 543
 544         cmd := exec.Command("go", "build", "-o", "ptrtest.exe")
 545         cmd.Dir = src
 546         cmd.Env = append(os.Environ(), "GOPATH="+gopath)
 547         out, err := cmd.CombinedOutput()
 548         if err != nil {
 549                 t.Fatalf("go build: %v\n%s", err, out)
 550         }
 551
 552         return dir, filepath.Join(src, "ptrtest.exe")
 553 }
 554
 555 const ptrTestMain = `
 556 func main() {
 557         for _, arg := range os.Args[1:] {
 558                 f := funcs[arg]
 559                 if f == nil {
 560                         panic("missing func "+arg)
 561                 }
 562                 f()
 563         }
 564 }
 565 `
 566
 567 var csem = make(chan bool, 16)
 568
 569 func testOne(t *testing.T, pt ptrTest, exe string) {
 570         t.Parallel()
 571
 572         // Run the tests in parallel, but don't run too many
 573         // executions in parallel, to avoid overloading the system.
 574         runcmd := func(cgocheck string) ([]byte, error) {
 575                 csem <- true
 576                 defer func() { <-csem }()
 577                 cmd := exec.Command(exe, pt.name)
 578                 cmd.Env = append(os.Environ(), "GODEBUG=cgocheck="+cgocheck)
 579                 return cmd.CombinedOutput()
 580         }
 581
 582         if pt.expensive {
 583                 buf, err := runcmd("1")
 584                 if err != nil {
 585                         t.Logf("%s", buf)
 586                         if pt.fail {
 587                                 t.Fatalf("test marked expensive, but failed when not expensive: %v", err)
 588                         } else {
 589                                 t.Errorf("failed unexpectedly with GODEBUG=cgocheck=1: %v", err)
 590                         }
 591                 }
 592
 593         }
 594
 595         cgocheck := ""
 596         if pt.expensive {
 597                 cgocheck = "2"
 598         }
 599
 600         buf, err := runcmd(cgocheck)
 601         if pt.fail {
 602                 if err == nil {
 603                         t.Logf("%s", buf)
 604                         t.Fatalf("did not fail as expected")
 605                 } else if !bytes.Contains(buf, []byte("Go pointer")) {
 606                         t.Logf("%s", buf)
 607                         t.Fatalf("did not print expected error (failed with %v)", err)
 608                 }
 609         } else {
 610                 if err != nil {
 611                         t.Logf("%s", buf)
 612                         t.Fatalf("failed unexpectedly: %v", err)
 613                 }
 614
 615                 if !pt.expensive {
 616                         // Make sure it passes with the expensive checks.
 617                         buf, err := runcmd("2")
 618                         if err != nil {
 619                                 t.Logf("%s", buf)
 620                                 t.Fatalf("failed unexpectedly with expensive checks: %v", err)
 621                         }
 622                 }
 623         }
 624
 625         if pt.fail {
 626                 buf, err := runcmd("0")
 627                 if err != nil {
 628                         t.Logf("%s", buf)
 629                         t.Fatalf("failed unexpectedly with GODEBUG=cgocheck=0: %v", err)
 630                 }
 631         }
 632 }