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/mheap.go b/libgo/go/runtime/mheap.go
index 65622f4..eb98083 100644
--- a/libgo/go/runtime/mheap.go
+++ b/libgo/go/runtime/mheap.go
@@ -1165,7 +1165,7 @@ func (h *mheap) scavenge(k int32, now, limit uint64) {
 	}
 }
 
-//go:linkname runtime_debug_freeOSMemory runtime_debug.freeOSMemory
+//go:linkname runtime_debug_freeOSMemory runtime..z2fdebug.freeOSMemory
 func runtime_debug_freeOSMemory() {
 	GC()
 	systemstack(func() { mheap_.scavenge(-1, ^uint64(0), 0) })