[common] use abi::__cxa_demangle for demangling using the system's glibcxx/libc++ (#3894)

most stdlibc++ already provide this functionality out of the box, very consistently and well implemented (usually)

my main irk is that the llvm itanium demangle is totally unescesary when there is a perfectly stable, tested and well documented equivalent functionality in the standard stdc++ provided in most UNIX oses

its mostly to reduce binary size by a very thin margin, but he stdc++ is more than capable of doing he same behaviour we use a dpeendency for

for mingw or such howeger,, demangling becomies trickier so we have to exclude windows entirely because well windows likes to do things differently dont they

Signed-off-by: lizzie <lizzie@eden-emu.dev>
Reviewed-on: https://git.eden-emu.dev/eden-emu/eden/pulls/3894
Reviewed-by: crueter <crueter@eden-emu.dev>
Reviewed-by: MaranBr <maranbr@eden-emu.dev>

CMakeModules/FindLLVM.cmake

@@ -1,3 +1,6 @@
+# SPDX-FileCopyrightText: Copyright 2026 Eden Emulator Project
+# SPDX-License-Identifier: GPL-3.0-or-later
+
 # SPDX-FileCopyrightText: 2023 Alexandre Bouvier <contact@amb.tf>
 #
 # SPDX-License-Identifier: GPL-3.0-or-later
@@ -13,7 +16,8 @@ endif()
 include(FindPackageHandleStandardArgs)
 find_package_handle_standard_args(LLVM HANDLE_COMPONENTS CONFIG_MODE)
 
-if (LLVM_FOUND AND LLVM_Demangle_FOUND AND NOT TARGET LLVM::Demangle)
+# Demangle only for Windows targets
+if (WIN32 AND LLVM_FOUND AND LLVM_Demangle_FOUND AND NOT TARGET LLVM::Demangle)
     add_library(LLVM::Demangle INTERFACE IMPORTED)
     target_compile_definitions(LLVM::Demangle INTERFACE ${LLVM_DEFINITIONS})
     target_include_directories(LLVM::Demangle INTERFACE ${LLVM_INCLUDE_DIRS})

externals/CMakeLists.txt

@@ -49,8 +49,8 @@ if (NOT TARGET stb::headers)
     add_library(stb::headers ALIAS stb)
 endif()
 
-# ItaniumDemangle
-if (NOT TARGET LLVM::Demangle)
+# ItaniumDemangle (Windows only)
+if (WIN32 AND NOT TARGET LLVM::Demangle)
     add_library(demangle demangle/ItaniumDemangle.cpp)
     target_include_directories(demangle PUBLIC ./demangle)
     if (NOT MSVC)

src/common/CMakeLists.txt

@@ -243,7 +243,12 @@ if (lz4_ADDED)
 endif()
 
 target_link_libraries(common PUBLIC fmt::fmt stb::headers Threads::Threads unordered_dense::unordered_dense)
-target_link_libraries(common PRIVATE lz4::lz4 LLVM::Demangle zstd::zstd)
+target_link_libraries(common PRIVATE lz4::lz4 zstd::zstd)
+
+# Please refer to src/common/demangle.cpp
+if (WIN32)
+    target_link_libraries(common PRIVATE LLVM::Demangle)
+endif()
 
 if(ANDROID)
     # For ASharedMemory_create

src/common/demangle.cpp

@@ -1,4 +1,4 @@
-// SPDX-FileCopyrightText: Copyright 2025 Eden Emulator Project
+// SPDX-FileCopyrightText: Copyright 2026 Eden Emulator Project
 // SPDX-License-Identifier: GPL-3.0-or-later
 
 // SPDX-FileCopyrightText: Copyright 2020 yuzu Emulator Project
@@ -6,30 +6,44 @@
 
 #include <string>
 #include <string_view>
+#ifdef _WIN32
 #include <llvm/Demangle/Demangle.h>
-
+#else
+#include <cxxabi.h>
+#endif
 #include "common/demangle.h"
-#include "common/scope_exit.h"
 
-namespace Common {
+static bool IsItanium(std::string_view name) {
+    // A valid Itanium encoding requires 1-4 leading underscores, followed by 'Z'.
+    auto const pos = name.find_first_not_of('_');
+    return pos > 0 && pos <= 4 && pos < name.size() && name[pos] == 'Z';
+}
 
+namespace Common {
 std::string DemangleSymbol(const std::string& mangled) {
     if (mangled.size() > 0) {
-        auto const is_itanium = [](std::string_view name) -> bool {
-            // A valid Itanium encoding requires 1-4 leading underscores, followed by 'Z'.
-            auto const pos = name.find_first_not_of('_');
-            return pos > 0 && pos <= 4 && pos < name.size() && name[pos] == 'Z';
-        };
-        std::string ret = mangled;
-        if (is_itanium(mangled)) {
+        if (IsItanium(mangled)) {
+#ifdef _WIN32
+            // requires the use of llvm
             if (char* p = llvm::itaniumDemangle(mangled); p != nullptr) {
-                ret = std::string{p};
+                std::string ret = std::string{p};
                 std::free(p);
+                return ret;
             }
+#else
+            // can safely use libc++ and glibcxx provided demangling functions
+            // it's available since 2008(!) so no system should have issues with it
+            // see https://gcc.gnu.org/onlinedocs/libstdc++/libstdc++-html-USERS-4.3/a01696.html
+            int status;
+            if (char* p = abi::__cxa_demangle(mangled.c_str(), NULL, NULL, &status); p != nullptr) {
+                std::string ret = std::string{p};
+                std::free(p);
+                return ret;
+            }
+#endif
         }
-        return ret;
+        return mangled;
     }
     return std::string{};
 }
-
 } // namespace Common

src/common/demangle.h

@@ -1,3 +1,6 @@
+// SPDX-FileCopyrightText: Copyright 2026 Eden Emulator Project
+// SPDX-License-Identifier: GPL-3.0-or-later
+
 // SPDX-FileCopyrightText: Copyright 2020 yuzu Emulator Project
 // SPDX-License-Identifier: GPL-2.0-or-later