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-rw-r--r--src/cmd/go/alldocs.go6
-rw-r--r--src/cmd/go/internal/help/helpdoc.go6
2 files changed, 12 insertions, 0 deletions
diff --git a/src/cmd/go/alldocs.go b/src/cmd/go/alldocs.go
index 46bca7480b..1029d1e8c2 100644
--- a/src/cmd/go/alldocs.go
+++ b/src/cmd/go/alldocs.go
@@ -2190,6 +2190,12 @@
// building the package for Windows; similarly, math_386.s will be included
// only when building the package for 32-bit x86.
//
+// By convention, packages with assembly implementations may provide a go-only
+// version under the "purego" build constraint. This does not limit the use of
+// cgo (use the "cgo" build constraint) or unsafe. For example:
+//
+// //go:build purego
+//
// Go versions 1.16 and earlier used a different syntax for build constraints,
// with a "// +build" prefix. The gofmt command will add an equivalent //go:build
// constraint when encountering the older syntax.
diff --git a/src/cmd/go/internal/help/helpdoc.go b/src/cmd/go/internal/help/helpdoc.go
index ab04ce001c..1d3ffefc97 100644
--- a/src/cmd/go/internal/help/helpdoc.go
+++ b/src/cmd/go/internal/help/helpdoc.go
@@ -1009,6 +1009,12 @@ Naming a file dns_windows.go will cause it to be included only when
building the package for Windows; similarly, math_386.s will be included
only when building the package for 32-bit x86.
+By convention, packages with assembly implementations may provide a go-only
+version under the "purego" build constraint. This does not limit the use of
+cgo (use the "cgo" build constraint) or unsafe. For example:
+
+ //go:build purego
+
Go versions 1.16 and earlier used a different syntax for build constraints,
with a "// +build" prefix. The gofmt command will add an equivalent //go:build
constraint when encountering the older syntax.