Export witness table and RTTI objects in compiled libraries. (#1514)

* Export witness table objects in compiled code.

- Ensure that witness tables are preceeded with `extern "C"` modifier in the generated C++ code.
- RTTI objects use the mangled name of the type directly, so that can be queried using the type's mangled name directly from the resulting DLL.
- Expose `Linkage::getTypeConformanceWitnessMangledName` to return the mangled name of witness tables to the host.
- Ensure that all witness tables (including those for associated types) have proper mangled name.

* Fix GCC error in Slang generated code.

1 files changed, 4 insertions, 0 deletions

diff --git a/source/slang/slang-compiler.h b/source/slang/slang-compiler.h
index 8996f5512..ac22270f8 100755
--- a/source/slang/slang-compiler.h
+++ b/source/slang/slang-compiler.h
@@ -1205,6 +1205,10 @@ namespace Slang
             SlangInt               targetIndex = 0,
             slang::LayoutRules     rules = slang::LayoutRules::Default,
             ISlangBlob**    outDiagnostics = nullptr) override;
+        SLANG_NO_THROW SlangResult SLANG_MCALL getTypeConformanceWitnessMangledName(
+            slang::TypeReflection* type,
+            slang::TypeReflection* interfaceType,
+            ISlangBlob** outNameBlob) override;
         SLANG_NO_THROW SlangResult SLANG_MCALL createCompileRequest(
             SlangCompileRequest**   outCompileRequest) override;