Refactored Print::validate() method to not throw an exception, but

to return a string with an error message instead. This was necessary
to avoid a hang-up on some Strawberry Perl distributions, when
a perl "croak" function is called after a C++ exception is caught.

lib/Slic3r/Print.pm

@@ -450,4 +450,13 @@ sub expanded_output_filepath {
     return $self->placeholder_parser->process($path);
 }
 
+# Wrapper around the C++ Slic3r::Print::validate()
+# to produce a Perl exception without a hang-up on some Strawberry perls.
+sub validate
+{
+    my $self = shift;
+    my $err = $self->_validate;
+    die $err . "\n" if (defined($err) && $err ne '');
+}
+
 1;

xs/src/libslic3r/Print.cpp

@@ -577,7 +577,7 @@ bool Print::has_skirt() const
         || this->has_infinite_skirt();
 }
 
-void
+std::string
 Print::validate() const
 {
     if (this->config.complete_objects) {
@@ -619,7 +619,7 @@ Print::validate() const
                     Polygon p = convex_hull;
                     p.translate(*copy);
                     if (intersects(a, p))
-                        throw PrintValidationException("Some objects are too close; your extruder will collide with them.");
+                        return "Some objects are too close; your extruder will collide with them.";
                     
                     union_(a, p, &a);
                 }
@@ -638,7 +638,7 @@ Print::validate() const
             // it will be printed as last one so its height doesn't matter
             object_height.pop_back();
             if (!object_height.empty() && object_height.back() > scale_(this->config.extruder_clearance_height.value))
-                throw PrintValidationException("Some objects are too tall and cannot be printed without extruder collisions.");
+                return "Some objects are too tall and cannot be printed without extruder collisions.";
         }
     } // end if (this->config.complete_objects)
     
@@ -646,16 +646,16 @@ Print::validate() const
         size_t total_copies_count = 0;
         FOREACH_OBJECT(this, i_object) total_copies_count += (*i_object)->copies().size();
         if (total_copies_count > 1)
-            throw PrintValidationException("The Spiral Vase option can only be used when printing a single object.");
+            return "The Spiral Vase option can only be used when printing a single object.";
         if (this->regions.size() > 1)
-            throw PrintValidationException("The Spiral Vase option can only be used when printing single material objects.");
+            return "The Spiral Vase option can only be used when printing single material objects.";
     }
     
     {
         // find the smallest nozzle diameter
         std::set<size_t> extruders = this->extruders();
         if (extruders.empty())
-            throw PrintValidationException("The supplied settings will cause an empty print.");
+            return "The supplied settings will cause an empty print.";
         
         std::set<double> nozzle_diameters;
         for (std::set<size_t>::iterator it = extruders.begin(); it != extruders.end(); ++it)
@@ -679,13 +679,15 @@ Print::validate() const
                 first_layer_min_nozzle_diameter = min_nozzle_diameter;
             }
             if (first_layer_height > first_layer_min_nozzle_diameter)
-                throw PrintValidationException("First layer height can't be greater than nozzle diameter");
+                return "First layer height can't be greater than nozzle diameter";
             
             // validate layer_height
             if (object->config.layer_height.value > min_nozzle_diameter)
-                throw PrintValidationException("Layer height can't be greater than nozzle diameter");
+                return "Layer height can't be greater than nozzle diameter";
         }
     }
+
+    return std::string();
 }
 
 // the bounding box of objects placed in copies position

xs/src/libslic3r/Print.hpp

@@ -4,7 +4,7 @@
 #include "libslic3r.h"
 #include <set>
 #include <vector>
-#include <stdexcept>
+#include <string>
 #include "BoundingBox.hpp"
 #include "Flow.hpp"
 #include "PrintConfig.hpp"
@@ -29,11 +29,6 @@ enum PrintObjectStep {
     posInfill, posSupportMaterial,
 };
 
-class PrintValidationException : public std::runtime_error {
-    public:
-    PrintValidationException(const std::string &error) : std::runtime_error(error) {};
-};
-
 // To be instantiated over PrintStep or PrintObjectStep enums.
 template <class StepType>
 class PrintState
@@ -203,7 +198,8 @@ class Print
     bool apply_config(DynamicPrintConfig config);
     bool has_infinite_skirt() const;
     bool has_skirt() const;
-    void validate() const;
+    // Returns an empty string if valid, otherwise returns an error message.
+    std::string validate() const;
     BoundingBox bounding_box() const;
     BoundingBox total_bounding_box() const;
     double skirt_first_layer_height() const;

xs/xsp/Print.xsp

@@ -219,14 +219,8 @@ _constant()
         %code%{ RETVAL = THIS->apply_config(*config); %};
     bool has_infinite_skirt();
     bool has_skirt();
-    void validate()
-        %code%{
-            try {
-                THIS->validate();
-            } catch (PrintValidationException &e) {
-                croak("%s\n", e.what());
-            }
-        %};
+    std::string _validate()
+        %code%{ RETVAL = THIS->validate(); %};
     Clone<BoundingBox> bounding_box();
     Clone<BoundingBox> total_bounding_box();
     double skirt_first_layer_height();