[llgo] cmd/gllgo: handle/ignore more flags

[axw]

Summary

This diff is to support Debian packaging,
which sets various hardening-rleated flags
in CFLAGS. They don't make sense for Go,
so we just ignore them.

[pcc]

cmd/gllgo/gllgo.go

329

You might want to add a TODO to enable the stack protector anyway; it could still be useful for protecting against the scenario where a C library called via cgo is manipulated into overwriting a Go stack frame.

331–335

It may be simpler to ignore everything beginning with -W, as some other distribution may be using some other set of warning flags.

[pcc]

Otherwise LGTM

[axw]

• Ignore all -W prefixes (apart from -Wl,)
• add TODO to handle -fstack-protector*

[axw]

This comment was removed by axw.

cmd/gllgo/gllgo.go

case strings.HasPrefix(args[0], "-fgccgo-path="):
       opts.gccgoPath = args[0][13:]
 
     case strings.HasPrefix(args[0], "-fgo-pkgpath="):
       opts.pkgpath = args[0][13:]
 
     case strings.HasPrefix(args[0], "-fgo-relative-import-path="):
       // TODO(pcc): Handle this.
 
+    case strings.HasPrefix(args[0], "-fstack-protector"):
+      // TODO(axw) set ssp function attributes. This can be useful
+      // even for Go, if it interfaces with code written in a non-
+      // memory safe language (e.g. via cgo).
+
+    case strings.HasPrefix(args[0], "-W"):
+      // Go doesn't do warnings. Ignore.
+
     case args[0] == "-fload-plugin":
       if len(args) == 1 {
         return opts, errors.New("missing argument after '-fload-plugin'")
       }
       opts.plugins = append(opts.plugins, args[1])
       consumedArgs = 2
 
     case args[0] == "-fno-toplevel-reorder":
       // This is a GCC-specific code generation option. Ignore.