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/8956
Reviewed-by: Ian Lance Taylor <iant@golang.org>

5 files changed, 0 insertions, 76 deletions

diff --git a/src/runtime/cgo/callbacks.go b/src/runtime/cgo/callbacks.go
index cbaf064bd8..1682341596 100644
--- a/src/runtime/cgo/callbacks.go
+++ b/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:
diff --git a/src/runtime/cgocall.go b/src/runtime/cgocall.go
index d4d0cf47c3..c01d616ca7 100644
--- a/src/runtime/cgocall.go
+++ b/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))
diff --git a/src/runtime/cgocallback.go b/src/runtime/cgocallback.go
index 20ce87d4ca..f93acaba03 100644
--- a/src/runtime/cgocallback.go
+++ b/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) {
diff --git a/src/runtime/mgc.go b/src/runtime/mgc.go
index bf916f841d..126b95a475 100644
--- a/src/runtime/mgc.go
+++ b/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.
diff --git a/src/runtime/runtime2.go b/src/runtime/runtime2.go
index cdbaebcc09..609c7cf6f6 100644
--- a/src/runtime/runtime2.go
+++ b/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