[release-branch.go1.14] cmd/go: permit CGO_LDFLAGS to appear in //go:ldflag

For #42565
Fixes #42566

Change-Id: If7cf39905d124dbd54dfac6a53ee38270498efed
Reviewed-on: https://go-review.googlesource.com/c/go/+/269818
Trust: Ian Lance Taylor <iant@golang.org>
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Jay Conrod <jayconrod@google.com>
(cherry picked from commit 782cf560db4c919790fdb476d1bbe18e5ddf5ffd)
Reviewed-on: https://go-review.googlesource.com/c/go/+/270080

diff --git a/src/cmd/go/internal/work/exec.go b/src/cmd/go/internal/work/exec.go
index 6e20c055fab317c57263fa82c173c0231e6330c0..a87bc802c1c0cc8419bc4ea6e7f58770448fb298 100644 (file)
--- a/src/cmd/go/internal/work/exec.go
+++ b/src/cmd/go/internal/work/exec.go
@@ -2687,6 +2687,21 @@ func (b *Builder) cgo(a *Action, cgoExe, objdir string, pcCFLAGS, pcLDFLAGS, cgo
                                idx = bytes.Index(src, []byte(cgoLdflag))
                        }
                }
+
+               // We expect to find the contents of cgoLDFLAGS in flags.
+               if len(cgoLDFLAGS) > 0 {
+               outer:
+                       for i := range flags {
+                               for j, f := range cgoLDFLAGS {
+                                       if f != flags[i+j] {
+                                               continue outer
+                                       }
+                               }
+                               flags = append(flags[:i], flags[i+len(cgoLDFLAGS):]...)
+                               break
+                       }
+               }
+
                if err := checkLinkerFlags("LDFLAGS", "go:cgo_ldflag", flags); err != nil {
                        return nil, nil, err
                }

diff --git a/src/cmd/go/testdata/script/ldflag.txt b/src/cmd/go/testdata/script/ldflag.txt
new file mode 100644 (file)
index 0000000..6ceb33b
--- /dev/null
+++ b/src/cmd/go/testdata/script/ldflag.txt
@@ -0,0 +1,44 @@
+# Issue #42565
+
+[!cgo] skip
+
+# We can't build package bad, which uses #cgo LDFLAGS.
+cd bad
+! go build
+stderr no-such-warning
+
+# We can build package ok with the same flags in CGO_LDFLAGS.
+env CGO_LDFLAGS=-Wno-such-warning -Wno-unknown-warning-option
+cd ../ok
+go build
+
+# Build a main program that actually uses LDFLAGS.
+cd ..
+go build -ldflags=-v
+
+# Because we passed -v the Go linker should print the external linker
+# command which should include the flag we passed in CGO_LDFLAGS.
+stderr no-such-warning
+
+-- go.mod --
+module ldflag
+
+-- bad/bad.go --
+package bad
+
+// #cgo LDFLAGS: -Wno-such-warning -Wno-unknown-warning
+import "C"
+
+func F() {}
+-- ok/ok.go --
+package ok
+
+import "C"
+
+func F() {}
+-- main.go --
+package main
+
+import _ "ldflag/ok"
+
+func main() {}