On Fri, Feb 7, 2025 at 2:59 PM 'Pierre Gimalac' via golang-nuts <golang-nuts@googlegroups.com> wrote: > > I noticed that when importing the std "plugin" package then (some ?) > unexported methods are kept in the binary. > > Disclaimer it's something I only observed on a complex binary, I could not > make a minimal reproducible example, so I'm probably misunderstanding > something. > > When using `-ldflags=-dumpdep` on my complex binary I was seeing something > like `type:*text/template.Template -> text/template.(*Template).execute`, so > just having the type `Template` makes the unexported method reachable. It > disappeared when removing the "plugin" import. > > I believe the associated code in the linker is > https://github.com/golang/go/blob/go1.23.6/src/cmd/link/internal/ld/deadcode.go#L455. > We can see that if we have reflect and the binary is dynamically linked (with > plugin or shared build modes), then unexported methods are also kept. Note > that when `dynlink` is true then `reflectSeen` is also set to true, so I > think you actually don't even need to use reflect for that to happen. > > I'm curious why ? The documentation of `Plugin.Lookup` says the symbol must > be exported https://pkg.go.dev/plugin#Plugin.Lookup . > I would have expected the first part of the condition to be `m.isExported() > && (d.reflectSeen || d.dynlink)` instead. > > This makes binaries importing "plugin" (and probably plugins and shared > builds too) significantly bigger, in my case removing the "plugin" import > reduced the size of various binaries by around 30%. > See https://github.com/containerd/containerd/issues/11202 and > https://github.com/DataDog/datadog-agent/pull/32538 for details.
As the comment in the linker code says, the linker is ensuring that all methods of any reachable interface are kept. An interface can have unexported methods, and in the general case we must keep any method that may satisfy that interface. Ian -- You received this message because you are subscribed to the Google Groups "golang-nuts" group. To unsubscribe from this group and stop receiving emails from it, send an email to golang-nuts+unsubscr...@googlegroups.com. To view this discussion visit https://groups.google.com/d/msgid/golang-nuts/CAOyqgcU2hfh6gNEKcDT-0TUrCaTarUVcXbxpHcb2kdY8A%3D8kcQ%40mail.gmail.com.
