Avoid compiler warnings from function pointer conversions

gcc8 -Wextra prints a warning when reinterpret_cast is used for conversion
between different types of function pointers. Avoid that by instead using
a union with members of the two types of function pointers.

See https://github.com/libsigcplusplus/libsigcplusplus/issues/1

2 files changed, 12 insertions, 3 deletions

diff --git a/tests/giomm_stream_vfuncs/main.cc b/tests/giomm_stream_vfuncs/main.cc
index df1cde20..ad42e989 100644
--- a/tests/giomm_stream_vfuncs/main.cc
+++ b/tests/giomm_stream_vfuncs/main.cc
@@ -160,7 +160,7 @@ int main(int, char**)
       return EXIT_FAILURE;
     }
   }
-  catch (Gio::Error e)
+  catch (const Gio::Error& e)
   {
     std::cout << "Gio error: " << e.what() << std::endl;
     return EXIT_FAILURE;
diff --git a/tests/glibmm_vector/main.cc b/tests/glibmm_vector/main.cc
index 31138cf0..0f039356 100644
--- a/tests/glibmm_vector/main.cc
+++ b/tests/glibmm_vector/main.cc
@@ -196,14 +196,23 @@ public:
 
   ~Cache()
   {
+    // Conversion between different types of function pointers with
+    // reinterpret_cast can make gcc8 print a warning.
+    // https://github.com/libsigcplusplus/libsigcplusplus/issues/1
+    union {
+      GFunc pf;
+      decltype(&g_object_unref) pou;
+    } u;
+    u.pou = &g_object_unref;
+
     if (glist_)
     {
-      g_list_foreach(glist_, reinterpret_cast<GFunc>(g_object_unref), nullptr);
+      g_list_foreach(glist_, u.pf, nullptr);
       g_list_free(glist_);
     }
     if (gslist_)
     {
-      g_slist_foreach(gslist_, reinterpret_cast<GFunc>(g_object_unref), nullptr);
+      g_slist_foreach(gslist_, u.pf, nullptr);
       g_slist_free(gslist_);
     }
     if (garray_)