Fix usage of is_trivially_copyable on older GCC (for real this time)

src/libslic3r/Fill/FillBase.hpp

@@ -11,6 +11,7 @@
 #include "../libslic3r.h"
 #include "../BoundingBox.hpp"
 #include "../PrintConfig.hpp"
+#include "../Utils.hpp"
 
 namespace Slic3r {
 
@@ -40,11 +41,7 @@ struct FillParams
     // in this case we don't try to make more continuous paths
     bool        complete;
 };
-#if (!defined __GNUC__) || __GNUC__ > 4
-// Older GCCs don't have std::is_trivially_copyable
-// cf. https://gcc.gnu.org/onlinedocs/gcc-4.9.4/libstdc++/manual/manual/status.html#status.iso.2011
-static_assert(std::is_trivially_copyable<FillParams>::value, "FillParams class is not POD (and it should be - see constructor).");
-#endif
+static_assert(IsTriviallyCopyable<FillParams>::value, "FillParams class is not POD (and it should be - see constructor).");
 
 class Fill
 {

src/libslic3r/Slicing.hpp

@@ -10,6 +10,7 @@
 #include <vector>
 
 #include "libslic3r.h"
+#include "Utils.hpp"
 namespace Slic3r
 {
 
@@ -93,7 +94,7 @@ struct SlicingParameters
     coordf_t 	object_print_z_min;
     coordf_t 	object_print_z_max;
 };
-static_assert(std::is_trivially_copyable<SlicingParameters>::value, "SlicingParameters class is not POD (and it should be - see constructor).");
+static_assert(IsTriviallyCopyable<SlicingParameters>::value, "SlicingParameters class is not POD (and it should be - see constructor).");
 
 
 // The two slicing parameters lead to the same layering as long as the variable layer thickness is not in action.

src/libslic3r/Utils.hpp

@@ -159,6 +159,16 @@ template<class T> size_t next_highest_power_of_2(T v,
 extern std::string xml_escape(std::string text);
 
 
+#if defined __GNUC__ & __GNUC__ < 5
+// Older GCCs don't have std::is_trivially_copyable
+// cf. https://gcc.gnu.org/onlinedocs/gcc-4.9.4/libstdc++/manual/manual/status.html#status.iso.2011
+#warning "GCC version < 5, faking std::is_trivially_copyable"
+template<typename T> struct IsTriviallyCopyable { static constexpr bool value = true; };
+#else
+template<typename T> struct IsTriviallyCopyable : public std::is_trivially_copyable<T> {};
+#endif
+
+
 class ScopeGuard
 {
 public: