Merge branch 'master' into encoding_add_full_support_for_marshalers_with_pointer_receivers

Author: zenovich

api/next/62516.txt

@@ -0,0 +1,4 @@
+pkg testing, method (*B) Chdir(string) #62516
+pkg testing, method (*F) Chdir(string) #62516
+pkg testing, method (*T) Chdir(string) #62516
+pkg testing, type TB interface, Chdir(string) #62516

doc/godebug.md

@@ -151,7 +151,18 @@ see the [runtime documentation](/pkg/runtime#hdr-Environment_Variables)
 and the [go command documentation](/cmd/go#hdr-Build_and_test_caching).
 
 ### Go 1.24
-Go 1.24 made XML marshaling consistent: custom marshalers ([`MarshalXML`](/pkg/encoding/xml#Marshaler), [`MarshalXMLAttr`](/pkg/encoding/xml#MarshalerAttr), [`MarshalText`](/pkg/encoding#TextMarshaler)) are now always called when appropriate no matter if their receivers are pointers or values even if the related data fields are non-addressable. Also, [`MarshalXMLAttr`](/pkg/encoding/xml#MarshalerAttr) and [`MarshalText`](/pkg/encoding#TextMarshaler) are now called when appropriate for struct fields marked as attribute/CDATA/chardata even if the field type is an interface. This behavior can be reverted with the [`xmlinconsistentmarshal` setting](/pkg/encoding/xml/#Marshal).
+Go 1.24 made XML marshaling consistent: custom marshalers ([`MarshalXML`](/pkg/encoding/xml#Marshaler),
+[`MarshalXMLAttr`](/pkg/encoding/xml#MarshalerAttr), [`MarshalText`](/pkg/encoding#TextMarshaler))
+are now always called when appropriate no matter if their receivers are pointers or values
+even if the related data fields are non-addressable. Also, [`MarshalXMLAttr`](/pkg/encoding/xml#MarshalerAttr)
+and [`MarshalText`](/pkg/encoding#TextMarshaler) are now called when appropriate for struct fields
+marked as attribute/CDATA/chardata even if the field type is an interface.
+This behavior can be reverted with the [`xmlinconsistentmarshal` setting](/pkg/encoding/xml/#Marshal).
+
+Go 1.24 changed the global [`math/rand.Seed`](/pkg/math/rand/#Seed) to be a
+no-op. This setting is controlled by the `randseednop` setting.
+For Go 1.24 it defaults to `randseednop=1`.
+Using `randseednop=0` reverts to the pre-Go 1.24 behavior.
 
 ### Go 1.23
 

doc/next/6-stdlib/99-minor/math/rand/67273.md

@@ -0,0 +1,3 @@
+Calls to the deprecated top-level [Seed] function no longer have any effect. To
+restore the old behavior set `GODEBUG=randseednop=0`. For more background see
+the proposal [#67273](/issue/67273).

doc/next/6-stdlib/99-minor/testing/62516.md

@@ -0,0 +1,2 @@
+The new [T.Chdir] and [B.Chdir] methods can be used to change the working
+directory for the duration of a test or benchmark.

src/bytes/bytes_test.go

@@ -489,7 +489,7 @@ func TestIndexRune(t *testing.T) {
 		{"a☺b☻c☹d\xe2\x98�\xff�\xed\xa0\x80", 0xD800, -1}, // Surrogate pair
 		{"a☺b☻c☹d\xe2\x98�\xff�\xed\xa0\x80", utf8.MaxRune + 1, -1},
 
-		// Test the cutover to to bytealg.Index when it is triggered in
+		// Test the cutover to bytealg.Index when it is triggered in
 		// the middle of rune that contains consecutive runs of equal bytes.
 		{"aaaaaKKKK\U000bc104", '\U000bc104', 17}, // cutover: (n + 16) / 8
 		{"aaaaaKKKK鄄", '鄄', 17},

src/cmd/cgo/doc.go

@@ -425,6 +425,30 @@ passing uninitialized C memory to Go code if the Go code is going to
 store pointer values in it. Zero out the memory in C before passing it
 to Go.
 
+# Optimizing calls of C code
+
+When passing a Go pointer to a C function the compiler normally ensures
+that the Go object lives on the heap. If the C function does not keep
+a copy of the Go pointer, and never passes the Go pointer back to Go code,
+then this is unnecessary. The #cgo noescape directive may be used to tell
+the compiler that no Go pointers escape via the named C function.
+If the noescape directive is used and the C function does not handle the
+pointer safely, the program may crash or see memory corruption.
+
+For example:
+
+	// #cgo noescape cFunctionName
+
+When a Go function calls a C function, it prepares for the C function to
+call back to a Go function. The #cgo nocallback directive may be used to
+tell the compiler that these preparations are not necessary.
+If the nocallback directive is used and the C function does call back into
+Go code, the program will panic.
+
+For example:
+
+	// #cgo nocallback cFunctionName
+
 # Special cases
 
 A few special C types which would normally be represented by a pointer

src/cmd/cgo/gcc.go

@@ -94,10 +94,8 @@ func (f *File) ProcessCgoDirectives() {
 				directive := fields[1]
 				funcName := fields[2]
 				if directive == "nocallback" {
-					fatalf("#cgo nocallback disabled until Go 1.23")
 					f.NoCallbacks[funcName] = true
 				} else if directive == "noescape" {
-					fatalf("#cgo noescape disabled until Go 1.23")
 					f.NoEscapes[funcName] = true
 				}
 			}

src/cmd/cgo/internal/test/test.go

@@ -117,8 +117,8 @@ int add(int x, int y) {
 
 // escape vs noescape
 
-// TODO(#56378): enable in Go 1.23:
-// #cgo noescape handleGoStringPointerNoescape
+#cgo noescape handleGoStringPointerNoescape
+#cgo nocallback handleGoStringPointerNoescape
 void handleGoStringPointerNoescape(void *s) {}
 
 void handleGoStringPointerEscape(void *s) {}

src/cmd/cgo/internal/testerrors/testdata/notmatchedcfunction.go

@@ -5,8 +5,7 @@
 package main
 
 /*
-// TODO(#56378): change back to "#cgo noescape noMatchedCFunction: no matched C function" in Go 1.23
-// ERROR MESSAGE: #cgo noescape disabled until Go 1.23
+// ERROR MESSAGE: #cgo noescape noMatchedCFunction: no matched C function
 #cgo noescape noMatchedCFunction
 */
 import "C"

src/cmd/cgo/out.go

@@ -104,6 +104,9 @@ func (p *Package) writeDefs() {
 		fmt.Fprintf(fgo2, "var _Cgo_always_false bool\n")
 		fmt.Fprintf(fgo2, "//go:linkname _Cgo_use runtime.cgoUse\n")
 		fmt.Fprintf(fgo2, "func _Cgo_use(interface{})\n")
+		fmt.Fprintf(fgo2, "//go:linkname _Cgo_keepalive runtime.cgoKeepAlive\n")
+		fmt.Fprintf(fgo2, "//go:noescape\n")
+		fmt.Fprintf(fgo2, "func _Cgo_keepalive(interface{})\n")
 	}
 	fmt.Fprintf(fgo2, "//go:linkname _Cgo_no_callback runtime.cgoNoCallback\n")
 	fmt.Fprintf(fgo2, "func _Cgo_no_callback(bool)\n")
@@ -639,17 +642,20 @@ func (p *Package) writeDefsFunc(fgo2 io.Writer, n *Name, callsMalloc *bool) {
 		fmt.Fprintf(fgo2, "\t_Cgo_no_callback(false)\n")
 	}
 
-	// skip _Cgo_use when noescape exist,
+	// Use _Cgo_keepalive instead of _Cgo_use when noescape & nocallback exist,
 	// so that the compiler won't force to escape them to heap.
-	if !p.noEscapes[n.C] {
-		fmt.Fprintf(fgo2, "\tif _Cgo_always_false {\n")
-		if d.Type.Params != nil {
-			for i := range d.Type.Params.List {
-				fmt.Fprintf(fgo2, "\t\t_Cgo_use(p%d)\n", i)
-			}
+	// Instead, make the compiler keep them alive by using _Cgo_keepalive.
+	touchFunc := "_Cgo_use"
+	if p.noEscapes[n.C] && p.noCallbacks[n.C] {
+		touchFunc = "_Cgo_keepalive"
+	}
+	fmt.Fprintf(fgo2, "\tif _Cgo_always_false {\n")
+	if d.Type.Params != nil {
+		for _, name := range paramnames {
+			fmt.Fprintf(fgo2, "\t\t%s(%s)\n", touchFunc, name)
 		}
-		fmt.Fprintf(fgo2, "\t}\n")
 	}
+	fmt.Fprintf(fgo2, "\t}\n")
 	fmt.Fprintf(fgo2, "\treturn\n")
 	fmt.Fprintf(fgo2, "}\n")
 }