From f613cc4088e3330e5feba40c68c929da3858cf36 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Mateusz=20=C5=81oskot?= <mateusz@loskot.net>
Date: Fri, 21 Sep 2018 18:42:27 +0200
Subject: [PATCH] Remove re-assignment of functor from for_each_pixel (Trac
 7092)

The assignment was superfluous in general case and incorrect in specific
case when the algorithm was given a lambda expression.
The copy assignment operator is defined as deleted for lambda
expressions.

Add minimal test for for_each_pixel algorithm to verify it compiles with
lambda expression.
---
 include/boost/gil/algorithm.hpp   |  2 +-
 test/algorithm/Jamfile            | 17 ++++++++++++++++
 test/algorithm/for_each_pixel.cpp | 32 +++++++++++++++++++++++++++++++
 3 files changed, 50 insertions(+), 1 deletion(-)
 create mode 100644 test/algorithm/Jamfile
 create mode 100644 test/algorithm/for_each_pixel.cpp

diff --git a/include/boost/gil/algorithm.hpp b/include/boost/gil/algorithm.hpp
index 5c8159450..c7226fddf 100644
--- a/include/boost/gil/algorithm.hpp
+++ b/include/boost/gil/algorithm.hpp
@@ -765,7 +765,7 @@ F for_each_pixel(const V& img, F fun) {
         return std::for_each(img.begin().x(), img.end().x(), fun);
     } else {
         for (std::ptrdiff_t y=0; y<img.height(); ++y)
-            fun = std::for_each(img.row_begin(y),img.row_end(y),fun);
+            std::for_each(img.row_begin(y),img.row_end(y),fun);
         return fun;
     }
 }
diff --git a/test/algorithm/Jamfile b/test/algorithm/Jamfile
new file mode 100644
index 000000000..f477d572d
--- /dev/null
+++ b/test/algorithm/Jamfile
@@ -0,0 +1,17 @@
+# Boost.GIL (Generic Image Library) - tests
+#
+# Copyright (c) 2018 Mateusz Loskot <mateusz at loskot dot net>
+#
+# Distributed under the Boost Software License, Version 1.0.
+# (See accompanying file LICENSE_1_0.txt or
+# copy at http://www.boost.org/LICENSE_1_0.txt)
+
+import testing ;
+
+project
+    : requirements
+    <include>$(BOOST_ROOT)
+    <include>..
+    ;
+
+run for_each_pixel.cpp ;
diff --git a/test/algorithm/for_each_pixel.cpp b/test/algorithm/for_each_pixel.cpp
new file mode 100644
index 000000000..28c5210ab
--- /dev/null
+++ b/test/algorithm/for_each_pixel.cpp
@@ -0,0 +1,32 @@
+//
+// Copyright 2018 Mateusz Loskot <mateusz at loskot dot net>
+//
+// Distributed under the Boost Software License, Version 1.0
+// See accompanying file LICENSE_1_0.txt or copy at
+// http://www.boost.org/LICENSE_1_0.txt
+//
+#include <boost/gil/algorithm.hpp>
+#include <boost/gil/image.hpp>
+
+#include <boost/core/lightweight_test.hpp>
+
+namespace gil = boost::gil;
+
+void test_lambda_expression()
+{
+    gil::gray8_pixel_t const gray128(128);
+    gil::gray8_image_t image(2, 2, gray128);
+
+    int sum{0};
+    gil::for_each_pixel(gil::view(image), [&sum](gil::gray8_pixel_t& p) {
+        sum += gil::at_c<0>(p);
+    });
+    BOOST_TEST(sum == 2 * 2 * 128);
+}
+
+int main()
+{
+    test_lambda_expression();
+
+    return boost::report_errors();
+}