From 61313dab524f2c82add8442e15d87fca5b7103de Mon Sep 17 00:00:00 2001 From: Xiangdong Ji Date: Sun, 18 Oct 2020 11:43:23 -0700 Subject: [PATCH] cmd/go: use the last -linkmode flag to determine external linking Current linkmode checking in determining package dependencies doesn't take multiple -linkmode options into consideration, may lead to redundant dependency on 'runtime/cgo'. Fixes the problem and adds a testcase. Change-Id: Iac5ea9fb3ca5ef931201afd0f3441f41f946c919 Reviewed-on: https://go-review.googlesource.com/c/go/+/263497 Trust: Jay Conrod Reviewed-by: Bryan C. Mills --- src/cmd/go/internal/load/pkg.go | 14 +++++++++----- src/cmd/go/testdata/script/gcflags_patterns.txt | 4 ++++ 2 files changed, 13 insertions(+), 5 deletions(-) diff --git a/src/cmd/go/internal/load/pkg.go b/src/cmd/go/internal/load/pkg.go index c9665265e9..f07bd3e075 100644 --- a/src/cmd/go/internal/load/pkg.go +++ b/src/cmd/go/internal/load/pkg.go @@ -1978,16 +1978,20 @@ func externalLinkingForced(p *Package) bool { // external linking mode, as of course does // -ldflags=-linkmode=external. External linking mode forces // an import of runtime/cgo. + // If there are multiple -linkmode options, the last one wins. pieCgo := cfg.BuildBuildmode == "pie" && !sys.InternalLinkPIESupported(cfg.BuildContext.GOOS, cfg.BuildContext.GOARCH) linkmodeExternal := false if p != nil { ldflags := BuildLdflags.For(p) - for i, a := range ldflags { - if a == "-linkmode=external" { - linkmodeExternal = true - } - if a == "-linkmode" && i+1 < len(ldflags) && ldflags[i+1] == "external" { + for i := len(ldflags) - 1; i >= 0; i-- { + a := ldflags[i] + if a == "-linkmode=external" || + a == "-linkmode" && i+1 < len(ldflags) && ldflags[i+1] == "external" { linkmodeExternal = true + break + } else if a == "-linkmode=internal" || + a == "-linkmode" && i+1 < len(ldflags) && ldflags[i+1] == "internal" { + break } } } diff --git a/src/cmd/go/testdata/script/gcflags_patterns.txt b/src/cmd/go/testdata/script/gcflags_patterns.txt index 5374493a43..f23cecefd3 100644 --- a/src/cmd/go/testdata/script/gcflags_patterns.txt +++ b/src/cmd/go/testdata/script/gcflags_patterns.txt @@ -63,6 +63,10 @@ stderr 'link.* -X=math.pi=3' go build -n -ldflags=-X=math.pi=3 stderr 'link.* -X=math.pi=3' +# cgo.a should not be a dependency of internally-linked go package +go build -ldflags='-linkmode=external -linkmode=internal' -n prog.go +! stderr 'packagefile .*runtime/cgo.a' + -- z1/z.go -- package z1 import _ "y" -- 2.48.1