[PATCH] Remove warnings from v0_mangle functions in rust-mangle.cc

[Mark Wielaard <mark@klomp.org>]

There were two warnings in rust-mangle.cc

rust-mangle.cc: In function ‘std::string Rust::Compile::v0_mangle_item
(const Rust::TyTy::BaseType*, const Rust::Resolver::CanonicalPath&, const string&)’:
rust-mangle.cc:198:1: warning: no return statement in function returning non-void

rust-mangle.cc: At global scope:
rust-mangle.cc:201:1: warning: ‘std::string Rust::Compile::v0_mangle_impl_item
(const Rust::TyTy::BaseType*, const Rust::TyTy::BaseType*, const string&, const string&)’
 declared ‘static’ but never defined [-Wunused-function]

The first results in undefined behaviour, the second points out that the
function isn't ever called/used.

Fix the first by adding a gcc_unreachable () to turn the calling of the
function into an abort ().  Fix the second by adding the call in
Mangler::mangle_impl_item. And add an implementation simply calling
gcc-unreachable (). This turns the warnings and undefined behaviour into
explicit runtime aborts when these functions are actually called.
---
 gcc/rust/backend/rust-mangle.cc | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

https://code.wildebeest.org/git/user/mjw/gccrs/commit/?h=rust-mangle-unreachable

diff --git a/gcc/rust/backend/rust-mangle.cc b/gcc/rust/backend/rust-mangle.cc
index 840acb992e0..0e6643c64ae 100644
--- a/gcc/rust/backend/rust-mangle.cc
+++ b/gcc/rust/backend/rust-mangle.cc
@@ -195,11 +195,15 @@ v0_mangle_item (const TyTy::BaseType *ty, const Resolver::CanonicalPath &path,
 		const std::string &crate_name)
 {
   auto ty_prefix = v0_type_prefix (ty);
+  gcc_unreachable ();
 }
 
 static std::string
 v0_mangle_impl_item (const TyTy::BaseType *self, const TyTy::BaseType *ty,
-		     const std::string &name, const std::string &crate_name);
+		     const std::string &name, const std::string &crate_name)
+{
+  gcc_unreachable ();
+}
 
 std::string
 Mangler::mangle_item (const TyTy::BaseType *ty,
@@ -227,7 +231,7 @@ Mangler::mangle_impl_item (const TyTy::BaseType *self, const TyTy::BaseType *ty,
     case Mangler::MangleVersion::LEGACY:
       return legacy_mangle_impl_item (self, ty, name, crate_name);
     case Mangler::MangleVersion::V0:
-      gcc_unreachable ();
+      return v0_mangle_impl_item (self, ty, name, crate_name);
     default:
       gcc_unreachable ();
     }
-- 
2.32.0