fix(gnovm): count slice allocations before performing memory allocati…

…ons (#2781)

<!-- please provide a detailed description of the changes made in this
pull request. -->
This is to fix the first issue mentioned in #2738.

In short, when allocating and reallocating slices' underlying arrays,
the VM was building the `TypedValue` slice before making the necessary
VM allocations. It is important the VM allocations be done before the
`TypedValue` allocations to ensure the values being allocated won't
exceed the VM's limit. In extreme cases, unchecked allocations resulted
in the VM hanging as it tried to allocate massive `TypedValue` slices in
the go runtime.
<details><summary>Contributors' checklist...</summary>

- [x] Added new tests, or not needed, or not feasible
- [x] Provided an example (e.g. screenshot) to aid review or the PR is
self-explanatory
- [x] Updated the official documentation or not needed
- [x] No breaking changes were made, or a `BREAKING CHANGE: xxx` message
was included in the description
- [x] Added references to related issues and PRs
- [x] Provided any useful hints for running manual tests
- [x] Added new benchmarks to [generated
graphs](https://gnoland.github.io/benchmarks), if any. More info
[here](https://github.com/gnolang/gno/blob/master/.benchmarks/README.md).
</details>

gno.land/cmd/gnoland/testdata/alloc_array.txtar

@@ -0,0 +1,16 @@
+loadpkg gno.land/r/alloc $WORK
+
+gnoland start
+
+! gnokey maketx call -pkgpath gno.land/r/alloc -func DoAlloc -gas-fee 1000000ugnot -gas-wanted 2000000 -broadcast -chainid=tendermint_test test1
+stderr 'Data: allocation limit exceeded'
+
+-- alloc.gno --
+package alloc
+
+var buffer interface{}
+
+func DoAlloc() {
+	var arr [1_000_000_000_000_000]byte
+	buffer = arr
+}

gno.land/cmd/gnoland/testdata/alloc_byte_slice.txtar

@@ -0,0 +1,16 @@
+loadpkg gno.land/r/alloc $WORK
+
+gnoland start
+
+! gnokey maketx call -pkgpath gno.land/r/alloc -func DoAlloc -gas-fee 1000000ugnot -gas-wanted 2000000 -broadcast -chainid=tendermint_test test1
+stderr 'Data: allocation limit exceeded'
+
+-- alloc.gno --
+package alloc
+
+var buffer []byte
+
+func DoAlloc() {
+ 	buffer := make([]byte, 1_000_000_000_000)
+  buffer[1] = 'a'
+}

gno.land/cmd/gnoland/testdata/alloc_slice.txtar

@@ -0,0 +1,16 @@
+loadpkg gno.land/r/alloc $WORK
+
+gnoland start
+
+! gnokey maketx call -pkgpath gno.land/r/alloc -func DoAlloc -gas-fee 1000000ugnot -gas-wanted 2000000 -broadcast -chainid=tendermint_test test1
+stderr 'Data: allocation limit exceeded'
+
+-- alloc.gno --
+package alloc
+
+var buffer []int
+
+func DoAlloc() {
+ 	buffer := make([]int, 1_000_000_000_000)
+  buffer[1] = 1
+}

gnovm/pkg/gnolang/alloc.go

@@ -223,7 +223,12 @@ func (alloc *Allocator) NewSlice(base Value, offset, length, maxcap int) *SliceV
 	}
 }
 
-// NOTE: also allocates the underlying array from list.
+// NewSliceFromList allocates a new slice with the underlying array value
+// populated from `list`. This should not be called from areas in the codebase
+// that are doing allocations with potentially large user provided values, e.g.
+// `make()` and `append()`. Using `Alloc.NewListArray` can be used is most cases
+// to allocate the space for the `TypedValue` list before doing the allocation
+// in the go runtime -- see the `make()` code in uverse.go.
 func (alloc *Allocator) NewSliceFromList(list []TypedValue) *SliceValue {
 	alloc.AllocateSlice()
 	alloc.AllocateListArray(int64(cap(list)))
@@ -238,7 +243,9 @@ func (alloc *Allocator) NewSliceFromList(list []TypedValue) *SliceValue {
 	}
 }
 
-// NOTE: also allocates the underlying array from data.
+// NewSliceFromData allocates a new slice with the underlying data array
+// value populated from `data`. See the doc for `NewSliceFromList` for
+// correct usage notes.
 func (alloc *Allocator) NewSliceFromData(data []byte) *SliceValue {
 	alloc.AllocateSlice()
 	alloc.AllocateDataArray(int64(cap(data)))

gnovm/pkg/gnolang/uverse.go

@@ -193,32 +193,32 @@ func UverseNode() *PackageNode {
 						return
 					} else if arg0Type.Elem().Kind() == Uint8Kind {
 						// append(nil, *SliceValue) new data bytes ---
-						data := make([]byte, arg1Length)
+						arrayValue := m.Alloc.NewDataArray(arg1Length)
 						if arg1Base.Data == nil {
 							copyListToData(
-								data[:arg1Length],
+								arrayValue.Data[:arg1Length],
 								arg1Base.List[arg1Offset:arg1EndIndex])
 						} else {
 							copy(
-								data[:arg1Length],
+								arrayValue.Data[:arg1Length],
 								arg1Base.Data[arg1Offset:arg1EndIndex])
 						}
 						m.PushValue(TypedValue{
 							T: arg0Type,
-							V: m.Alloc.NewSliceFromData(data),
+							V: m.Alloc.NewSlice(arrayValue, 0, arg1Length, arg1Length),
 						})
 						return
 					} else {
 						// append(nil, *SliceValue) new list ---------
-						list := make([]TypedValue, arg1Length)
-						if 0 < arg1Length {
+						arrayValue := m.Alloc.NewListArray(arg1Length)
+						if arg1Length > 0 {
 							for i := 0; i < arg1Length; i++ {
-								list[i] = arg1Base.List[arg1Offset+i].unrefCopy(m.Alloc, m.Store)
+								arrayValue.List[i] = arg1Base.List[arg1Offset+i].unrefCopy(m.Alloc, m.Store)
 							}
 						}
 						m.PushValue(TypedValue{
 							T: arg0Type,
-							V: m.Alloc.NewSliceFromList(list),
+							V: m.Alloc.NewSlice(arrayValue, 0, arg1Length, arg1Length),
 						})
 						return
 					}
@@ -236,27 +236,27 @@ func UverseNode() *PackageNode {
 						return
 					} else if arg0Type.Elem().Kind() == Uint8Kind {
 						// append(nil, *NativeValue) new data bytes --
-						data := make([]byte, arg1NativeValueLength)
+						arrayValue := m.Alloc.NewDataArray(arg1NativeValueLength)
 						copyNativeToData(
-							data[:arg1NativeValueLength],
+							arrayValue.Data[:arg1NativeValueLength],
 							arg1NativeValue, arg1NativeValueLength)
 						m.PushValue(TypedValue{
 							T: arg0Type,
-							V: m.Alloc.NewSliceFromData(data),
+							V: m.Alloc.NewSlice(arrayValue, 0, arg1NativeValueLength, arg1NativeValueLength),
 						})
 						return
 					} else {
 						// append(nil, *NativeValue) new list --------
-						list := make([]TypedValue, arg1NativeValueLength)
-						if 0 < arg1NativeValueLength {
+						arrayValue := m.Alloc.NewListArray(arg1NativeValueLength)
+						if arg1NativeValueLength > 0 {
 							copyNativeToList(
 								m.Alloc,
-								list[:arg1NativeValueLength],
+								arrayValue.List[:arg1NativeValueLength],
 								arg1NativeValue, arg1NativeValueLength)
 						}
 						m.PushValue(TypedValue{
 							T: arg0Type,
-							V: m.Alloc.NewSliceFromList(list),
+							V: m.Alloc.NewSlice(arrayValue, 0, arg1NativeValueLength, arg1NativeValueLength),
 						})
 						return
 					}
@@ -344,63 +344,65 @@ func UverseNode() *PackageNode {
 						}
 					} else if arg0Type.Elem().Kind() == Uint8Kind {
 						// append(*SliceValue, *SliceValue) new data bytes ---
-						data := make([]byte, arg0Length+arg1Length)
+						newLength := arg0Length + arg1Length
+						arrayValue := m.Alloc.NewDataArray(newLength)
 						if 0 < arg0Length {
 							if arg0Base.Data == nil {
 								copyListToData(
-									data[:arg0Length],
+									arrayValue.Data[:arg0Length],
 									arg0Base.List[arg0Offset:arg0Offset+arg0Length])
 							} else {
 								copy(
-									data[:arg0Length],
+									arrayValue.Data[:arg0Length],
 									arg0Base.Data[arg0Offset:arg0Offset+arg0Length])
 							}
 						}
 						if 0 < arg1Length {
 							if arg1Base.Data == nil {
 								copyListToData(
-									data[arg0Length:arg0Length+arg1Length],
+									arrayValue.Data[arg0Length:newLength],
 									arg1Base.List[arg1Offset:arg1Offset+arg1Length])
 							} else {
 								copy(
-									data[arg0Length:arg0Length+arg1Length],
+									arrayValue.Data[arg0Length:newLength],
 									arg1Base.Data[arg1Offset:arg1Offset+arg1Length])
 							}
 						}
 						m.PushValue(TypedValue{
 							T: arg0Type,
-							V: m.Alloc.NewSliceFromData(data),
+							V: m.Alloc.NewSlice(arrayValue, 0, newLength, newLength),
 						})
 						return
 					} else {
 						// append(*SliceValue, *SliceValue) new list ---------
-						list := make([]TypedValue, arg0Length+arg1Length)
-						if 0 < arg0Length {
+						arrayLen := arg0Length + arg1Length
+						arrayValue := m.Alloc.NewListArray(arrayLen)
+						if arg0Length > 0 {
 							if arg0Base.Data == nil {
 								for i := 0; i < arg0Length; i++ {
-									list[i] = arg0Base.List[arg0Offset+i].unrefCopy(m.Alloc, m.Store)
+									arrayValue.List[i] = arg0Base.List[arg0Offset+i].unrefCopy(m.Alloc, m.Store)
 								}
 							} else {
 								panic("should not happen")
 							}
 						}
 
-						if 0 < arg1Length {
+						if arg1Length > 0 {
 							if arg1Base.Data == nil {
 								for i := 0; i < arg1Length; i++ {
-									list[arg0Length+i] = arg1Base.List[arg1Offset+i].unrefCopy(m.Alloc, m.Store)
+									arrayValue.List[arg0Length+i] = arg1Base.List[arg1Offset+i].unrefCopy(m.Alloc, m.Store)
 								}
 							} else {
 								copyDataToList(
-									list[arg0Length:arg0Length+arg1Length],
+									arrayValue.List[arg0Length:arg0Length+arg1Length],
 									arg1Base.Data[arg1Offset:arg1Offset+arg1Length],
 									arg1Type.Elem(),
 								)
 							}
 						}
 						m.PushValue(TypedValue{
 							T: arg0Type,
-							V: m.Alloc.NewSliceFromList(list),
+							V: m.Alloc.NewSlice(arrayValue, 0, arrayLen, arrayLen),
 						})
 						return
 					}
@@ -441,46 +443,47 @@ func UverseNode() *PackageNode {
 						}
 					} else if arg0Type.Elem().Kind() == Uint8Kind {
 						// append(*SliceValue, *NativeValue) new data bytes --
-						data := make([]byte, arg0Length+arg1NativeValueLength)
+						newLength := arg0Length + arg1NativeValueLength
+						arrayValue := m.Alloc.NewDataArray(newLength)
 						if 0 < arg0Length {
 							if arg0Base.Data == nil {
 								copyListToData(
-									data[:arg0Length],
+									arrayValue.Data[:arg0Length],
 									arg0Base.List[arg0Offset:arg0Offset+arg0Length])
 							} else {
 								copy(
-									data[:arg0Length],
+									arrayValue.Data[:arg0Length],
 									arg0Base.Data[arg0Offset:arg0Offset+arg0Length])
 							}
 						}
 						if 0 < arg1NativeValueLength {
 							copyNativeToData(
-								data[arg0Length:arg0Length+arg1NativeValueLength],
+								arrayValue.Data[arg0Length:newLength],
 								arg1NativeValue, arg1NativeValueLength)
 						}
 						m.PushValue(TypedValue{
 							T: arg0Type,
-							V: m.Alloc.NewSliceFromData(data),
+							V: m.Alloc.NewSlice(arrayValue, 0, newLength, newLength),
 						})
 						return
 					} else {
 						// append(*SliceValue, *NativeValue) new list --------
 						listLen := arg0Length + arg1NativeValueLength
-						list := make([]TypedValue, listLen)
+						arrayValue := m.Alloc.NewListArray(listLen)
 						if 0 < arg0Length {
 							for i := 0; i < listLen; i++ {
-								list[i] = arg0Base.List[arg0Offset+i].unrefCopy(m.Alloc, m.Store)
+								arrayValue.List[i] = arg0Base.List[arg0Offset+i].unrefCopy(m.Alloc, m.Store)
 							}
 						}
 						if 0 < arg1NativeValueLength {
 							copyNativeToList(
 								m.Alloc,
-								list[arg0Length:listLen],
+								arrayValue.List[arg0Length:listLen],
 								arg1NativeValue, arg1NativeValueLength)
 						}
 						m.PushValue(TypedValue{
 							T: arg0Type,
-							V: m.Alloc.NewSliceFromList(list),
+							V: m.Alloc.NewSlice(arrayValue, 0, listLen, listLen),
 						})
 						return
 					}
@@ -779,25 +782,25 @@ func UverseNode() *PackageNode {
 					lv := vargs.TV.GetPointerAtIndexInt(m.Store, 0).Deref()
 					li := lv.ConvertGetInt()
 					if et.Kind() == Uint8Kind {
-						data := make([]byte, li)
+						arrayValue := m.Alloc.NewDataArray(li)
 						m.PushValue(TypedValue{
 							T: tt,
-							V: m.Alloc.NewSliceFromData(data),
+							V: m.Alloc.NewSlice(arrayValue, 0, li, li),
 						})
 						return
 					} else {
-						list := make([]TypedValue, li)
+						arrayValue := m.Alloc.NewListArray(li)
 						if et.Kind() == InterfaceKind {
 							// leave as is
 						} else {
 							// init zero elements with concrete type.
 							for i := 0; i < li; i++ {
-								list[i] = defaultTypedValue(m.Alloc, et)
+								arrayValue.List[i] = defaultTypedValue(m.Alloc, et)
 							}
 						}
 						m.PushValue(TypedValue{
 							T: tt,
-							V: m.Alloc.NewSliceFromList(list),
+							V: m.Alloc.NewSlice(arrayValue, 0, li, li),
 						})
 						return
 					}
@@ -807,30 +810,37 @@ func UverseNode() *PackageNode {
 					cv := vargs.TV.GetPointerAtIndexInt(m.Store, 1).Deref()
 					ci := cv.ConvertGetInt()
 					if et.Kind() == Uint8Kind {
-						data := make([]byte, li, ci)
+						arrayValue := m.Alloc.NewDataArray(ci)
 						m.PushValue(TypedValue{
 							T: tt,
-							V: m.Alloc.NewSliceFromData(data),
+							V: m.Alloc.NewSlice(arrayValue, 0, li, ci),
 						})
 						return
 					} else {
-						list := make([]TypedValue, li, ci)
+						arrayValue := m.Alloc.NewListArray(ci)
 						if et := bt.Elem(); et.Kind() == InterfaceKind {
 							// leave as is
 						} else {
-							// init zero elements with concrete type.
-							// the elements beyond len l within cap c
-							// must also be initialized, for a future
-							// slice operation may refer to them.
-							// XXX can this be removed?
-							list2 := list[:ci]
+							// Initialize all elements within capacity with default
+							// type values. These need to be initialized because future
+							// slice operations could get messy otherwise. Simple capacity
+							// expansions like `a = a[:cap(a)]` would make it trivial to
+							// initialize zero values at the time of the slice operation.
+							// But sequences of operations like:
+							// 		a := make([]int, 1, 10)
+							// 		a = a[7:cap(a)]
+							// 		a = a[3:5]
+							//
+							// require a bit more work to handle correctly, requiring that
+							// all new TypedValue slice elements be checked to ensure they have
+							// a value for every slice operation, which is not desirable.
 							for i := 0; i < ci; i++ {
-								list2[i] = defaultTypedValue(m.Alloc, et)
+								arrayValue.List[i] = defaultTypedValue(m.Alloc, et)
 							}
 						}
 						m.PushValue(TypedValue{
 							T: tt,
-							V: m.Alloc.NewSliceFromList(list),
+							V: m.Alloc.NewSlice(arrayValue, 0, li, ci),
 						})
 						return
 					}