fix cppcorecheck warnings (#703)

* Added c++17 test configurations for clang5.0 and clang6.0

* Fixed CppCoreCheck warnings in GSL and tests

- Added CMakeSettings.json for VS Open Folder configuration
	- So we can easily run CppCoreCheck in VS
- Fixed CppCorecheck warnings where it made sense
- Suppressed the rest
	- Some suppression does not work due to compiler/tool bugs,
          so replaced by #pragma disable
	- CppCoreCheck has noise, suppressed those with comments
	- Catch produces many warnings, blanket-supressed them all
- Had to fix clang formatting to keep attributes in place
	- clang-format does not support attributes, so I am using
        - "CommentPragmas: '^ NO-FORMAT:'" to skip formatiting on them
- Removed GSL_NOEXCEPT macro, removed incorred noexcepts

* Ignore unknown attributes

* ignore unknown attributes in noexception mode tests

* fixed C26472 in at()

* created GSL_SUPPRESS macro to allow all compilers to parse suppression attributes

* try to fix gcc compilation problems with attributes

* ignore gsl::suppress for gcc

* move suppression to function level on return statements

clang5.0 and up does not allow attributes on return statemets in constexpr functions

* move suppression to function level on return statements

* use GSL_SUPPRESS in algorithm_tests

* Addressed PR comments

1 files changed, 31 insertions, 20 deletions

diff --git a/tests/algorithm_tests.cpp b/tests/algorithm_tests.cpp
index 388d17d..368b53d 100644
--- a/tests/algorithm_tests.cpp
+++ b/tests/algorithm_tests.cpp
@@ -14,6 +14,12 @@
 //
 ///////////////////////////////////////////////////////////////////////////////
 
+#ifdef _MSC_VER
+// blanket turn off warnings from CppCoreCheck from catch
+// so people aren't annoyed by them when running the tool.
+#pragma warning(disable : 26440 26426) // from catch
+#endif
+
 #include <catch/catch.hpp> // for AssertionHandler, StringRef, CHECK, CHE...
 
 #include <gsl/gsl_algorithm> // for copy
@@ -29,6 +35,8 @@ struct fail_fast;
 using namespace std;
 using namespace gsl;
 
+GSL_SUPPRESS(bounds.4) // NO-FORMAT: attribute
+GSL_SUPPRESS(bounds.2) // NO-FORMAT: attribute
 TEST_CASE("same_type")
 {
     // dynamic source and destination span
@@ -36,8 +44,8 @@ TEST_CASE("same_type")
         std::array<int, 5> src{1, 2, 3, 4, 5};
         std::array<int, 10> dst{};
 
-        span<int> src_span(src);
-        span<int> dst_span(dst);
+        const span<int> src_span(src);
+        const span<int> dst_span(dst);
 
         copy(src_span, dst_span);
         copy(src_span, dst_span.subspan(src_span.size()));
@@ -53,8 +61,8 @@ TEST_CASE("same_type")
         std::array<int, 5> src{1, 2, 3, 4, 5};
         std::array<int, 10> dst{};
 
-        span<int, 5> src_span(src);
-        span<int> dst_span(dst);
+        const span<int, 5> src_span(src);
+        const span<int> dst_span(dst);
 
         copy(src_span, dst_span);
         copy(src_span, dst_span.subspan(src_span.size()));
@@ -70,8 +78,8 @@ TEST_CASE("same_type")
         std::array<int, 5> src{1, 2, 3, 4, 5};
         std::array<int, 10> dst{};
 
-        span<int> src_span(src);
-        span<int, 10> dst_span(dst);
+        const span<int> src_span(src);
+        const span<int, 10> dst_span(dst);
 
         copy(src_span, dst_span);
         copy(src_span, dst_span.subspan(src_span.size()));
@@ -87,8 +95,8 @@ TEST_CASE("same_type")
         std::array<int, 5> src{1, 2, 3, 4, 5};
         std::array<int, 10> dst{};
 
-        span<int, 5> src_span(src);
-        span<int, 10> dst_span(dst);
+        const span<int, 5> src_span(src);
+        const span<int, 10> dst_span(dst);
 
         copy(src_span, dst_span);
         copy(src_span, dst_span.subspan(src_span.size()));
@@ -100,6 +108,9 @@ TEST_CASE("same_type")
     }
 }
 
+
+GSL_SUPPRESS(bounds.4) // NO-FORMAT: attribute
+GSL_SUPPRESS(bounds.2) // NO-FORMAT: attribute
 TEST_CASE("compatible_type")
 {
     // dynamic source and destination span
@@ -107,8 +118,8 @@ TEST_CASE("compatible_type")
         std::array<short, 5> src{1, 2, 3, 4, 5};
         std::array<int, 10> dst{};
 
-        span<short> src_span(src);
-        span<int> dst_span(dst);
+        const span<short> src_span(src);
+        const span<int> dst_span(dst);
 
         copy(src_span, dst_span);
         copy(src_span, dst_span.subspan(src_span.size()));
@@ -124,8 +135,8 @@ TEST_CASE("compatible_type")
         std::array<short, 5> src{1, 2, 3, 4, 5};
         std::array<int, 10> dst{};
 
-        span<short, 5> src_span(src);
-        span<int> dst_span(dst);
+        const span<short, 5> src_span(src);
+        const span<int> dst_span(dst);
 
         copy(src_span, dst_span);
         copy(src_span, dst_span.subspan(src_span.size()));
@@ -141,8 +152,8 @@ TEST_CASE("compatible_type")
         std::array<short, 5> src{1, 2, 3, 4, 5};
         std::array<int, 10> dst{};
 
-        span<short> src_span(src);
-        span<int, 10> dst_span(dst);
+        const span<short> src_span(src);
+        const span<int, 10> dst_span(dst);
 
         copy(src_span, dst_span);
         copy(src_span, dst_span.subspan(src_span.size()));
@@ -158,8 +169,8 @@ TEST_CASE("compatible_type")
         std::array<short, 5> src{1, 2, 3, 4, 5};
         std::array<int, 10> dst{};
 
-        span<short, 5> src_span(src);
-        span<int, 10> dst_span(dst);
+        const span<short, 5> src_span(src);
+        const span<int, 10> dst_span(dst);
 
         copy(src_span, dst_span);
         copy(src_span, dst_span.subspan(src_span.size()));
@@ -195,10 +206,10 @@ TEST_CASE("small_destination_span")
     std::array<int, 12> src{1, 2, 3, 4};
     std::array<int, 4> dst{};
 
-    span<int> src_span_dyn(src);
-    span<int, 12> src_span_static(src);
-    span<int> dst_span_dyn(dst);
-    span<int, 4> dst_span_static(dst);
+    const span<int> src_span_dyn(src);
+    const span<int, 12> src_span_static(src);
+    const span<int> dst_span_dyn(dst);
+    const span<int, 4> dst_span_static(dst);
 
     CHECK_THROWS_AS(copy(src_span_dyn, dst_span_dyn), fail_fast);
     CHECK_THROWS_AS(copy(src_span_dyn, dst_span_static), fail_fast);