Export std hash template specializations from dylibs

CMakeLists.txt

@@ -462,6 +462,10 @@ if(BUILD_STATIC_LIB)
 else()
   message(STATUS "Building libbinaryen as shared library.")
   add_library(binaryen SHARED)
+  if(LINUX)
+    # Disable interposition and resolve Binaryen symbols locally.
+    add_link_flag("-Bsymbolic")
+  endif()
 endif()
 target_link_libraries(binaryen Threads::Threads)
 if(BUILD_LLVM_DWARF)

src/compiler-support.h

@@ -31,4 +31,23 @@
 #define WASM_BUILTIN_UNREACHABLE __assume(false)
 #endif
 
+// Forces symbols to be exported from libbinaryen dynamic library. Currently
+// we are just using the default flags, causing most of our symbols to have
+// "default" visibility, meaning they can all be used from the tool sources.
+// However a recent libc++ change caused functions declared in namespace std
+// (e.g. hash template specializations) to have hidden visibility, inherited.
+// from the namespece (see https://github.com/llvm/llvm-project/pull/131156).
+// So this macro forces them to be exported. Currently it is only applied to
+// the hash specializations that are defined in libbinaryen and used in the
+// tool code. In the future if we want to compile libbinaryen with
+// -fvisibility-hidden or use a DLL on Windows, we'll need
+// to explicitly annotate everything we want to export. But that's probably
+// only useful if we want external users to link against libbinaryen.so
+// (currently we don't; it's only used to reduce our install size).
+#if defined(__ELF__) || defined(__MACH__)
+#define DLLEXPORT [[gnu::visibility("default")]]
+#else
+#define DLLEXPORT
+#endif
+
 #endif // wasm_compiler_support_h

src/wasm-type-shape.h

@@ -20,6 +20,7 @@
 #include <functional>
 #include <vector>
 
+#include "compiler-support.h"
 #include "wasm-features.h"
 #include "wasm-type.h"
 
@@ -74,7 +75,7 @@ namespace std {
 
 template<> class hash<wasm::RecGroupShape> {
 public:
-  size_t operator()(const wasm::RecGroupShape& shape) const;
+  DLLEXPORT size_t operator()(const wasm::RecGroupShape& shape) const;
 };
 
 } // namespace std

src/wasm-type.h

@@ -25,6 +25,7 @@
 #include <variant>
 #include <vector>
 
+#include "compiler-support.h"
 #include "support/index.h"
 #include "support/name.h"
 #include "support/parent_index_iterator.h"
@@ -1005,35 +1006,35 @@ namespace std {
 
 template<> class hash<wasm::Type> {
 public:
-  size_t operator()(const wasm::Type&) const;
+  DLLEXPORT size_t operator()(const wasm::Type&) const;
 };
 template<> class hash<wasm::Signature> {
 public:
-  size_t operator()(const wasm::Signature&) const;
+  DLLEXPORT size_t operator()(const wasm::Signature&) const;
 };
 template<> class hash<wasm::Continuation> {
 public:
-  size_t operator()(const wasm::Continuation&) const;
+  DLLEXPORT size_t operator()(const wasm::Continuation&) const;
 };
 template<> class hash<wasm::Field> {
 public:
-  size_t operator()(const wasm::Field&) const;
+  DLLEXPORT size_t operator()(const wasm::Field&) const;
 };
 template<> class hash<wasm::Struct> {
 public:
-  size_t operator()(const wasm::Struct&) const;
+  DLLEXPORT size_t operator()(const wasm::Struct&) const;
 };
 template<> class hash<wasm::Array> {
 public:
-  size_t operator()(const wasm::Array&) const;
+  DLLEXPORT size_t operator()(const wasm::Array&) const;
 };
 template<> class hash<wasm::HeapType> {
 public:
-  size_t operator()(const wasm::HeapType&) const;
+  DLLEXPORT size_t operator()(const wasm::HeapType&) const;
 };
 template<> class hash<wasm::RecGroup> {
 public:
-  size_t operator()(const wasm::RecGroup&) const;
+  DLLEXPORT size_t operator()(const wasm::RecGroup&) const;
 };
 
 } // namespace std