Fix -Wsubobject-linkage warning (#6243)

* Fix -Wsubobject-linkage warning

Having tk::spline header-only implementation included from
SmallAreaInfillFlowCompensator.hpp makes
SmallAreaInfillFlowCompensator::flowModel have separate (albeit the
same) implementation in each translation unit.

In order to fix this issue, SmallAreaInfillFlowCompensator::flowModel
converted to opaque 'pimpl'

* spline: remove anonymous namespace

Remove outer anonymous namespace from splice.h to make
forward declaration for tk::spline possible.

src/libslic3r/GCode/SmallAreaInfillFlowCompensator.cpp

@@ -15,6 +15,7 @@
 #include "../PrintConfig.hpp"
 
 #include "SmallAreaInfillFlowCompensator.hpp"
+#include "spline/spline.h"
 #include <boost/log/trivial.hpp>
 
 namespace Slic3r {
@@ -79,6 +80,9 @@ SmallAreaInfillFlowCompensator::SmallAreaInfillFlowCompensator(const Slic3r::GCo
         BOOST_LOG_TRIVIAL(error) << "Error parsing small area infill compensation model: " << e.what();
     }
 }
+
+SmallAreaInfillFlowCompensator::~SmallAreaInfillFlowCompensator() = default;
+
 double SmallAreaInfillFlowCompensator::flow_comp_model(const double line_length)
 {
     if(flowModel == nullptr)

src/libslic3r/GCode/SmallAreaInfillFlowCompensator.hpp

@@ -4,25 +4,20 @@
 #include "../libslic3r.h"
 #include "../PrintConfig.hpp"
 #include "../ExtrusionEntity.hpp"
-#include "spline/spline.h"
 #include <memory>
 
-namespace Slic3r {
+namespace tk {
+class spline;
+} // namespace tk
 
-#ifndef _WIN32
-// Currently on Linux/macOS, this class spits out large amounts of subobject linkage
-// warnings because of the flowModel field. tk::spline is in an anonymous namespace which
-// causes this issue. Until the issue can be solved, this is a temporary solution.
-#pragma GCC diagnostic push
-#pragma GCC diagnostic ignored "-Wsubobject-linkage"
-#endif
+namespace Slic3r {
 
 class SmallAreaInfillFlowCompensator
 {
 public:
     SmallAreaInfillFlowCompensator() = delete;
     explicit SmallAreaInfillFlowCompensator(const Slic3r::GCodeConfig& config);
-    ~SmallAreaInfillFlowCompensator() = default;
+    ~SmallAreaInfillFlowCompensator();
 
     double modify_flow(const double line_length, const double dE, const ExtrusionRole role);
 
@@ -39,10 +34,6 @@ private:
     double max_modified_length() { return eLengths.back(); }
 };
 
-#ifndef _WIN32
-#pragma GCC diagnostic pop
-#endif
-
 } // namespace Slic3r
 
 #endif /* slic3r_GCode_SmallAreaInfillFlowCompensator_hpp_ */

src/spline/spline.h

@@ -46,11 +46,6 @@
 #pragma GCC diagnostic ignored "-Wunused-function"
 #endif
 
-// unnamed namespace only because the implementation is in this
-// header file and we don't want to export symbols to the obj files
-namespace
-{
-
 namespace tk
 {
 
@@ -942,8 +937,6 @@ std::vector<double> solve_cubic(double a, double b, double c, double d,
 } // namespace tk
 
 
-} // namespace
-
 #if !defined(_MSC_VER)
 #pragma GCC diagnostic pop
 #endif