Treat warnings as errors (#2490)

dlib/test/geometry.cpp

@@ -367,6 +367,19 @@ namespace
             }
         }
 
+        {
+            const rectangle input(1,1,6,4); 
+            const rectangle output = set_rect_area(input,4*input.area());
+            DLIB_TEST(output.area() == 4*input.area());
+            DLIB_TEST(output.width() == 2*input.width());
+            DLIB_TEST(output.height() == 2*input.height());
+
+            const auto input_center = center(input);
+            const auto output_center = center(output);
+            DLIB_TEST(std::abs(input_center.x() - output_center.x()) <= 1);
+            DLIB_TEST(std::abs(input_center.y() - output_center.y()) <= 1);
+        }
+
     }
 
 // ----------------------------------------------------------------------------------------

dlib/test/gui/main.cpp

@@ -411,7 +411,6 @@ public:
         group1(*this),
         group2(*this),
         group3(*this),
-        keyboard_count(1),
         keydown(*this),
         keyup(*this),
         l1(*this),
@@ -759,7 +758,6 @@ private:
     widget_group group1;
     widget_group group2;
     widget_group group3;
-    int keyboard_count;
     label keydown;
     label keyup;
     label l1;

dlib/test/invoke.cpp

@@ -323,6 +323,9 @@ namespace
         static_assert(dlib::invoke(multiply_ints, 2, 5) == 10, "this should be constexpr");
         static_assert(dlib::invoke_r<long>(multiply_ints, 2, 5) == 10, "this should be constexpr");
         constexpr constexpr_object constexpr_obj;
+#if defined (_MSC_VER)
+        constexpr_obj; // avoid warning C4101: 'constexpr_obj': unreferenced local variable
+#endif
         static_assert(dlib::invoke(&constexpr_object::multiply_ints, constexpr_obj, 2, 5) == 10, "this should be constexpr");
         static_assert(dlib::invoke_r<long>(&constexpr_object::multiply_ints, constexpr_obj, 2, 5) == 10, "this should be constexpr");
     }

dlib/unordered_pair.h

@@ -65,6 +65,14 @@ namespace dlib
                 - #first and #second contain copies of the items a and b.
         !*/ {}
 
+        unordered_pair (
+            const unordered_pair& p
+        ) = default;
+        /*!
+            ensures
+                - #*this is a copy of p
+        !*/
+
         template <typename U>
         unordered_pair (
             const unordered_pair <U>& p

examples/dnn_instance_segmentation_train_ex.cpp

@@ -29,9 +29,6 @@
 #include <dlib/dir_nav.h>
 #include <iterator>
 #include <thread>
-#if __cplusplus >= 201703L || (defined(_MSVC_LANG) && _MSVC_LANG >= 201703L)
-#include <execution>
-#endif // __cplusplus >= 201703L
 
 using namespace std;
 using namespace dlib;
@@ -555,14 +552,13 @@ std::vector<std::vector<truth_instance>> load_all_truth_instances(const std::vec
 {
     std::vector<std::vector<truth_instance>> truth_instances(listing.size());
 
-    std::transform(
-#if __cplusplus >= 201703L || (defined(_MSVC_LANG) && _MSVC_LANG >= 201703L)
-        std::execution::par,
-#endif // __cplusplus >= 201703L
-        listing.begin(),
-        listing.end(),
-        truth_instances.begin(),
-        load_truth_instances
+    parallel_for(
+        0,
+        listing.size(),
+        [&](size_t index)
+        {
+            truth_instances[index] = load_truth_instances(listing[index]);
+        }
     );
 
     return truth_instances;

examples/object_detector_advanced_ex.cpp

@@ -179,7 +179,7 @@ public:
     inline friend void serialize   ( const very_simple_feature_extractor& item, std::ostream& out)  { serialize(item.feat_image, out); }
     inline friend void deserialize ( very_simple_feature_extractor& item, std::istream& in ) { deserialize(item.feat_image, in); }
 
-    void copy_configuration ( const very_simple_feature_extractor& item){}
+    void copy_configuration ( const very_simple_feature_extractor&){}
 
 private:
     array2d<unsigned char> feat_image;

examples/server_iostream_ex.cpp

@@ -34,10 +34,10 @@ class serv : public server_iostream
         std::istream& in,
         std::ostream& out,
         const std::string& foreign_ip,
-        const std::string& local_ip,
-        unsigned short foreign_port,
-        unsigned short local_port,
-        uint64 connection_id
+        const std::string& /*local_ip*/,
+        unsigned short /*foreign_port*/,
+        unsigned short /*local_port*/,
+        uint64 /*connection_id*/
     )
     {
         // The details of the connection are contained in the last few arguments to