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, 4 insertions, 3 deletions

diff --git a/gcc/go/gofrontend/lex.h b/gcc/go/gofrontend/lex.h
index cf3de8d..75e37f8 100644
--- a/gcc/go/gofrontend/lex.h
+++ b/gcc/go/gofrontend/lex.h
@@ -440,6 +440,10 @@ class Lex
   static bool
   is_unicode_space(unsigned int c);
 
+  // Convert the specified hex char into an unsigned integer value.
+  static unsigned
+  hex_val(char c);
+
  private:
   ssize_t
   get_line();
@@ -462,9 +466,6 @@ class Lex
   octal_value(char c)
   { return c - '0'; }
 
-  static unsigned
-  hex_val(char c);
-
   Token
   make_invalid_token()
   { return Token::make_invalid_token(this->location()); }