runtime: delete cgo_allocate

This memory is untyped and can't be used anymore.
The next version of SWIG won't need it.

Change-Id: I592b287c5f5186975ee09a9b28d8efe3b57134e7
Reviewed-on: https://go-review.googlesource.com/8956Reviewed-by: Ian Lance Taylor <iant@golang.org>

misc/cgo/test/callback.go

@@ -9,7 +9,6 @@ void callback(void *f);
 void callGoFoo(void);
 void callGoStackCheck(void);
 void callPanic(void);
-void callCgoAllocate(void);
 int callGoReturnVal(void);
 int returnAfterGrow(void);
 int returnAfterGrowFromGo(void);
@@ -17,7 +16,6 @@ int returnAfterGrowFromGo(void);
 import "C"
 
 import (
-	"os"
 	"path"
 	"runtime"
 	"strings"
@@ -211,23 +209,6 @@ func testPanicFromC(t *testing.T) {
 	C.callPanic()
 }
 
-func testAllocateFromC(t *testing.T) {
-	if strings.Contains(os.Getenv("GODEBUG"), "wbshadow=") {
-		// This test is writing pointers to Go heap objects from C.
-		// As such, those writes have no write barriers, and
-		// wbshadow=2 mode correctly discovers that and crashes.
-		// Disable test if any wbshadow mode is enabled.
-		// TODO(rsc): I am not sure whether the test is fundamentally
-		// incompatible with concurrent collection and should be
-		// turned off or rewritten entirely. The test is attempting to
-		// mimic some SWIG behavior, so it is important to work
-		// through what we expect before trying SWIG and C++
-		// with the concurrent collector.
-		t.Skip("test is incompatible with wbshadow=")
-	}
-	C.callCgoAllocate() // crashes or exits on failure
-}
-
 // Test that C code can return a value if it calls a Go function that
 // causes a stack copy.
 func testReturnAfterGrow(t *testing.T) {

misc/cgo/test/callback_c_gc.c

@@ -23,58 +23,3 @@ callPanic(void)
 	crosscall2(_cgo_panic, &a, sizeof a);
 	*(int*)1 = 1;
 }
-
-/* Test calling cgo_allocate from C. This is what SWIG does. */
-
-typedef struct List List;
-struct List
-{
-	List *next;
-	int x;
-};
-
-void
-callCgoAllocate(void)
-{
-	int i;
-	struct { size_t n; void *ret; } a;
-	List *l, *head, **tail;
-
-	// Make sure this doesn't crash.
-	// And make sure it returns non-nil.
-	a.n = 0;
-	a.ret = 0;
-	crosscall2(_cgo_allocate, &a, sizeof a);
-	if(a.ret == 0) {
-		fprintf(stderr, "callCgoAllocate: alloc 0 returned nil\n");
-		exit(2);
-	}
-	
-	head = 0;
-	tail = &head;
-	for(i=0; i<100; i++) {
-		a.n = sizeof *l;
-		crosscall2(_cgo_allocate, &a, sizeof a);
-		l = a.ret;
-		l->x = i;
-		l->next = 0;
-		*tail = l;
-		tail = &l->next;
-	}
-	
-	gc();
-	
-	l = head;
-	for(i=0; i<100; i++) {
-		if(l->x != i) {
-			fprintf(stderr, "callCgoAllocate: lost memory\n");
-			exit(2);
-		}
-		l = l->next;
-	}
-	if(l != 0) {
-		fprintf(stderr, "callCgoAllocate: lost memory\n");
-		exit(2);
-	}
-}
-

misc/cgo/test/callback_c_gccgo.c

@@ -19,52 +19,3 @@ callPanic(void)
 {
 	_cgo_panic("panic from C");
 }
-
-/* Test calling cgo_allocate from C. This is what SWIG does. */
-
-typedef struct List List;
-struct List
-{
-	List *next;
-	int x;
-};
-
-void
-callCgoAllocate(void)
-{
-	int i;
-	List *l, *head, **tail;
-	
-	// Make sure this doesn't crash.
-	// And make sure it returns non-nil.
-	if(_cgo_allocate(0) == 0) {
-		fprintf(stderr, "callCgoAllocate: alloc 0 returned nil\n");
-		exit(2);
-	}
-
-	head = 0;
-	tail = &head;
-	for(i=0; i<100; i++) {
-		l = _cgo_allocate(sizeof *l);
-		l->x = i;
-		l->next = 0;
-		*tail = l;
-		tail = &l->next;
-	}
-	
-	gc();
-	
-	l = head;
-	for(i=0; i<100; i++) {
-		if(l->x != i) {
-			fprintf(stderr, "callCgoAllocate: lost memory\n");
-			exit(2);
-		}
-		l = l->next;
-	}
-	if(l != 0) {
-		fprintf(stderr, "callCgoAllocate: lost memory\n");
-		exit(2);
-	}
-}
-

misc/cgo/test/cgo_test.go

@@ -23,7 +23,6 @@ func TestCallbackPanic(t *testing.T)         { testCallbackPanic(t) }
 func TestCallbackPanicLoop(t *testing.T)     { testCallbackPanicLoop(t) }
 func TestCallbackPanicLocked(t *testing.T)   { testCallbackPanicLocked(t) }
 func TestPanicFromC(t *testing.T)            { testPanicFromC(t) }
-func TestAllocateFromC(t *testing.T)         { testAllocateFromC(t) }
 func TestZeroArgCallback(t *testing.T)       { testZeroArgCallback(t) }
 func TestBlocking(t *testing.T)              { testBlocking(t) }
 func Test1328(t *testing.T)                  { test1328(t) }

src/runtime/cgo/callbacks.go

@@ -22,32 +22,6 @@ func _runtime_cgocallback(unsafe.Pointer, unsafe.Pointer, uintptr)
 //go:cgo_export_static crosscall2
 //go:cgo_export_dynamic crosscall2
 
-// Allocate memory.  This allocates the requested number of bytes in
-// memory controlled by the Go runtime.  The allocated memory will be
-// zeroed.  You are responsible for ensuring that the Go garbage
-// collector can see a pointer to the allocated memory for as long as
-// it is valid, e.g., by storing a pointer in a local variable in your
-// C function, or in memory allocated by the Go runtime.  If the only
-// pointers are in a C global variable or in memory allocated via
-// malloc, then the Go garbage collector may collect the memory.
-
-// Call like this in code compiled with gcc:
-//   struct { size_t len; void *ret; } a;
-//   a.len = /* number of bytes to allocate */;
-//   crosscall2(_cgo_allocate, &a, sizeof a);
-//   /* Here a.ret is a pointer to the allocated memory.  */
-
-//go:linkname _runtime_cgo_allocate_internal runtime._cgo_allocate_internal
-var _runtime_cgo_allocate_internal byte
-
-//go:linkname _cgo_allocate _cgo_allocate
-//go:cgo_export_static _cgo_allocate
-//go:cgo_export_dynamic _cgo_allocate
-//go:nosplit
-func _cgo_allocate(a unsafe.Pointer, n int32) {
-	_runtime_cgocallback(unsafe.Pointer(&_runtime_cgo_allocate_internal), a, uintptr(n))
-}
-
 // Panic.  The argument is converted into a Go string.
 
 // Call like this in code compiled with gcc:

src/runtime/cgocall.go

@@ -132,12 +132,6 @@ func cgocall_errno(fn, arg unsafe.Pointer) int32 {
 //go:nosplit
 func endcgo(mp *m) {
 	mp.ncgo--
-	if mp.ncgo == 0 {
-		// We are going back to Go and are not in a recursive
-		// call.  Let the GC collect any memory allocated via
-		// _cgo_allocate that is no longer referenced.
-		mp.cgomal = nil
-	}
 
 	if raceenabled {
 		raceacquire(unsafe.Pointer(&racecgosync))

src/runtime/cgocallback.go

@@ -4,35 +4,8 @@
 
 package runtime
 
-import "unsafe"
-
 // These functions are called from C code via cgo/callbacks.go.
 
-// Allocate memory.  This allocates the requested number of bytes in
-// memory controlled by the Go runtime.  The allocated memory will be
-// zeroed.  You are responsible for ensuring that the Go garbage
-// collector can see a pointer to the allocated memory for as long as
-// it is valid, e.g., by storing a pointer in a local variable in your
-// C function, or in memory allocated by the Go runtime.  If the only
-// pointers are in a C global variable or in memory allocated via
-// malloc, then the Go garbage collector may collect the memory.
-//
-// TODO(rsc,iant): This memory is untyped.
-// Either we need to add types or we need to stop using it.
-
-func _cgo_allocate_internal(len uintptr) unsafe.Pointer {
-	if len == 0 {
-		len = 1
-	}
-	ret := unsafe.Pointer(&make([]unsafe.Pointer, (len+ptrSize-1)/ptrSize)[0])
-	c := new(cgomal)
-	c.alloc = ret
-	gp := getg()
-	c.next = gp.m.cgomal
-	gp.m.cgomal = c
-	return ret
-}
-
 // Panic.
 
 func _cgo_panic_internal(p *byte) {

src/runtime/mgc.go

@@ -127,15 +127,6 @@ const (
 	_RootCount       = 5
 )
 
-//go:linkname weak_cgo_allocate go.weak.runtime._cgo_allocate_internal
-var weak_cgo_allocate byte
-
-// Is _cgo_allocate linked into the binary?
-//go:nowritebarrier
-func have_cgo_allocate() bool {
-	return &weak_cgo_allocate != nil
-}
-
 // heapminimum is the minimum number of bytes in the heap.
 // This cleans up the corner case of where we have a very small live set but a lot
 // of allocations and collecting every GOGC * live set is expensive.

src/runtime/runtime2.go

@@ -283,7 +283,6 @@ type m struct {
 	fastrand      uint32
 	ncgocall      uint64 // number of cgo calls in total
 	ncgo          int32  // number of cgo calls currently in progress
-	cgomal        *cgomal
 	park          note
 	alllink       *m // on allm
 	schedlink     *m
@@ -485,13 +484,6 @@ type lfnode struct {
 	pushcnt uintptr
 }
 
-// Track memory allocated by code not written in Go during a cgo call,
-// so that the garbage collector can see them.
-type cgomal struct {
-	next  *cgomal
-	alloc unsafe.Pointer
-}
-
 // Indicates to write barrier and sychronization task to preform.
 const (
 	_GCoff             = iota // GC not running, write barrier disabled