compiler: improve name mangling for packpaths

    
    The current implementation of Gogo::pkgpath_for_symbol was written in
    a way that allowed two distinct package paths to map to the same
    symbol, which could cause collisions at link- time or compile-time.
    
    Switch to a better mangling scheme to insure that we get a unique
    packagepath symbol for each package. In the new scheme instead of having
    separate mangling schemes for identifiers and package paths, the
    main identifier mangler ("go_encode_id") now handles mangling of
    both packagepath characters and identifier characters.
    
    The new mangling scheme is more intrusive: "foo/bar.Baz" is mangled as
    "foo..z2fbar.Baz" instead of "foo_bar.Baz". To mitigate this, this
    patch also adds a demangling capability so that function names
    returned from runtime.CallersFrames are converted back to their
    original unmangled form.
    
    Changing the pkgpath_for_symbol scheme requires updating a number of
    //go:linkname directives and C "__asm__" directives to match the new
    scheme, as well as updating the 'gotest' driver (which makes
    assumptions about the correct mapping from pkgpath symbol to package
    name).
    
    Fixes golang/go#27534.
    
    Reviewed-on: https://go-review.googlesource.com/c/135455

From-SVN: r265510

1 files changed, 1 insertions, 1 deletions

diff --git a/libgo/go/runtime/mgc.go b/libgo/go/runtime/mgc.go
index 4ef982d..de84084 100644
--- a/libgo/go/runtime/mgc.go
+++ b/libgo/go/runtime/mgc.go
@@ -219,7 +219,7 @@ func gcenable() {
 	memstats.enablegc = true // now that runtime is initialized, GC is okay
 }
 
-//go:linkname setGCPercent runtime_debug.setGCPercent
+//go:linkname setGCPercent runtime..z2fdebug.setGCPercent
 func setGCPercent(in int32) (out int32) {
 	lock(&mheap_.lock)
 	out = gcpercent