Fix NDK version in Android CI

GCC 4.8.0 - 7.0 has a bug (https://gcc.gnu.org/bugzilla/show_bug.cgi?id=56480) involving specialization in a namespace enclosing the specialized template. This PR fixes an appearance of this bug in the span header.

.github/workflows/android.yml

@@ -29,7 +29,7 @@ jobs:
           echo "Emulator starting"
 
       - name: Configure
-        run: cmake -Werror=dev -DCMAKE_TOOLCHAIN_FILE=$ANDROID_HOME/ndk-bundle/build/cmake/android.toolchain.cmake -DANDROID_PLATFORM=16 -DANDROID_ABI=x86_64 -DCMAKE_BUILD_TYPE=Debug ..
+        run: cmake -Werror=dev -DCMAKE_TOOLCHAIN_FILE=$ANDROID_NDK_LATEST_HOME/build/cmake/android.toolchain.cmake -DANDROID_PLATFORM=16 -DANDROID_ABI=x86_64 -DCMAKE_BUILD_TYPE=Debug ..
 
       - name: Build
         run: cmake --build . --parallel

CMakeLists.txt

@@ -4,7 +4,7 @@ list(APPEND CMAKE_MODULE_PATH "${CMAKE_CURRENT_SOURCE_DIR}/cmake/")
 include(guidelineSupportLibrary)
 
 project(GSL
-    VERSION 3.1.0
+    VERSION 4.0.0
     LANGUAGES CXX
 )
 

README.md

@@ -85,17 +85,25 @@ This is based on [CppCoreGuidelines semi-specification](https://github.com/isocp
 [cg-concepts]: https://github.com/isocpp/CppCoreGuidelines/blob/master/CppCoreGuidelines.md#gslconcept-concepts
 
 # Quick Start
-## Supported Compilers
-The GSL officially supports the current and previous major release of MSVC, GCC, Clang, and XCode's Apple-Clang.
-See our latest test results for the most up-to-date list of supported configurations.
+## Supported Compilers / Toolsets
+The GSL officially supports the latest and previous major versions of VS with MSVC & LLVM, GCC, Clang, and XCode with Apple-Clang.
+Within these two major versions, we try to target the latest minor updates / revisions (although this may be affected by
+delays between a toolchain's release and when it becomes widely available for use).
+Below is a table showing the versions currently being tested.
 
 Compiler |Toolset Versions Currently Tested
 :------- |--:
- XCode |11.4 & 10.3
- GCC |9 & 8
- Clang |11 &  10
- Visual Studio with MSVC | VS2017 (15.9) & VS2019 (16.4) 
- Visual Studio with LLVM | VS2017 (Clang 9) & VS2019 (Clang 10)
+ XCode | 13.2.1 & 12.5.1
+ GCC | 11[^1] & 10[^2]
+ Clang | 12[^2] & 11[^2]
+ Visual Studio with MSVC | VS2022[^3] & VS2019[^4]
+ Visual Studio with LLVM | VS2022[^3] & VS2019[^4]
+
+
+[^1]: Precise version may be found in the [latest CI results](https://dev.azure.com/cppstat/GSL/_build?definitionId=1&branchFilter=26).
+[^2]: Precise version may be found in the [latest CI results](https://dev.azure.com/cppstat/GSL/_build?definitionId=1&branchFilter=26). Should be the version specified [here](https://github.com/actions/virtual-environments/blob/main/images/linux/Ubuntu2004-Readme.md#language-and-runtime).
+[^3]: Precise version may be found in the [latest CI results](https://dev.azure.com/cppstat/GSL/_build?definitionId=1&branchFilter=26). Should be the version specified [here](https://github.com/actions/virtual-environments/blob/main/images/win/Windows2022-Readme.md#visual-studio-enterprise-2022).
+[^4]: Precise version may be found in the [latest CI results](https://dev.azure.com/cppstat/GSL/_build?definitionId=1&branchFilter=26). Should be the version specified [here](https://github.com/actions/virtual-environments/blob/main/images/win/Windows2019-Readme.md#visual-studio-enterprise-2019).
 
 ---
 If you successfully port GSL to another platform, we would love to hear from you!

SECURITY.md

@@ -0,0 +1,41 @@
+<!-- BEGIN MICROSOFT SECURITY.MD V0.0.7 BLOCK -->
+
+## Security
+
+Microsoft takes the security of our software products and services seriously, which includes all source code repositories managed through our GitHub organizations, which include [Microsoft](https://github.com/Microsoft), [Azure](https://github.com/Azure), [DotNet](https://github.com/dotnet), [AspNet](https://github.com/aspnet), [Xamarin](https://github.com/xamarin), and [our GitHub organizations](https://opensource.microsoft.com/).
+
+If you believe you have found a security vulnerability in any Microsoft-owned repository that meets [Microsoft's definition of a security vulnerability](https://aka.ms/opensource/security/definition), please report it to us as described below.
+
+## Reporting Security Issues
+
+**Please do not report security vulnerabilities through public GitHub issues.**
+
+Instead, please report them to the Microsoft Security Response Center (MSRC) at [https://msrc.microsoft.com/create-report](https://aka.ms/opensource/security/create-report).
+
+If you prefer to submit without logging in, send email to [secure@microsoft.com](mailto:secure@microsoft.com).  If possible, encrypt your message with our PGP key; please download it from the [Microsoft Security Response Center PGP Key page](https://aka.ms/opensource/security/pgpkey).
+
+You should receive a response within 24 hours. If for some reason you do not, please follow up via email to ensure we received your original message. Additional information can be found at [microsoft.com/msrc](https://aka.ms/opensource/security/msrc). 
+
+Please include the requested information listed below (as much as you can provide) to help us better understand the nature and scope of the possible issue:
+
+  * Type of issue (e.g. buffer overflow, SQL injection, cross-site scripting, etc.)
+  * Full paths of source file(s) related to the manifestation of the issue
+  * The location of the affected source code (tag/branch/commit or direct URL)
+  * Any special configuration required to reproduce the issue
+  * Step-by-step instructions to reproduce the issue
+  * Proof-of-concept or exploit code (if possible)
+  * Impact of the issue, including how an attacker might exploit the issue
+
+This information will help us triage your report more quickly.
+
+If you are reporting for a bug bounty, more complete reports can contribute to a higher bounty award. Please visit our [Microsoft Bug Bounty Program](https://aka.ms/opensource/security/bounty) page for more details about our active programs.
+
+## Preferred Languages
+
+We prefer all communications to be in English.
+
+## Policy
+
+Microsoft follows the principle of [Coordinated Vulnerability Disclosure](https://aka.ms/opensource/security/cvd).
+
+<!-- END MICROSOFT SECURITY.MD BLOCK -->

azure-pipelines.yml

@@ -4,65 +4,63 @@ trigger:
 pr:
   autoCancel: true
 
-# GCC
 stages:
 - stage: GCC
   dependsOn: []
-  variables:
-  - name: CC
-    value: gcc
-  - name: CXX
-    value: g++
   jobs:
   - template: ./pipelines/jobs.yml
     parameters:
-      jobName: 'Validate GCC latest'
-      imageName: ubuntu-20.04
-  - template: ./pipelines/jobs.yml
-    parameters:
-      jobName: 'Validate GCC Previous'
-      imageName: ubuntu-18.04
+      compiler: gcc
+      image: ubuntu-20.04
+      compilerVersions: [ 11, 10 ]
+      setupfile: 'setup_gcc.yml'
 
-# Clang
 - stage: Clang
   dependsOn: []
-  variables:
-  - name: CC
-    value: clang
-  - name: CXX
-    value: clang++
   jobs:
   - template: ./pipelines/jobs.yml
     parameters:
-      jobName: 'Validate Clang latest'
-      imageName: ubuntu-20.04
-  - template: ./pipelines/jobs.yml
-    parameters:
-      jobName: 'Validate Clang Previous'
-      imageName: ubuntu-18.04
+      compiler: clang
+      image: ubuntu-20.04
+      compilerVersions: [ 12, 11 ]
+      setupfile: 'setup_clang.yml'
 
-# MSVC
-- stage: MSVC
+- stage: Xcode
   dependsOn: []
   jobs:
   - template: ./pipelines/jobs.yml
     parameters:
-      jobName: 'Validate MSVC latest'
-      imageName: windows-latest
-  - template: ./pipelines/jobs.yml
-    parameters:
-      jobName: 'Validate MSVC Previous'
-      imageName: vs2017-win2016
+      compiler: 'Xcode'
+      image: macOS-11
+      compilerVersions: [ '12.5.1', '13.2.1' ]
+      setupfile: 'setup_apple.yml'
 
-# Apple-Clang
-- stage: Apple_Clang
+- stage: VS_MSVC
   dependsOn: []
   jobs:
   - template: ./pipelines/jobs.yml
     parameters:
-      jobName: 'Validate Apple-Clang latest'
-      imageName: macos-10.15
+      compiler: 'VS2019 (MSVC)'
+      compilerVersions: [ 'default' ]
+      image: windows-2019
   - template: ./pipelines/jobs.yml
     parameters:
-      jobName: 'Validate Apple-Clang Previous'
-      imageName: macos-10.14
+      compiler: 'VS2022 (MSVC)'
+      compilerVersions: [ 'default' ]
+      image: windows-2022
+
+- stage: VS_LLVM
+  dependsOn: []
+  jobs:
+  - template: ./pipelines/jobs.yml
+    parameters:
+      compiler: 'VS2019 (LLVM)'
+      compilerVersions: [ 'default' ]
+      image: windows-2019
+      extraCmakeArgs: '-T ClangCL'
+  - template: ./pipelines/jobs.yml
+    parameters:
+      compiler: 'VS2022 (LLVM)'
+      compilerVersions: [ 'default' ]
+      image: windows-2022
+      extraCmakeArgs: '-T ClangCL'

include/gsl/algorithm

@@ -17,8 +17,8 @@
 #ifndef GSL_ALGORITHM_H
 #define GSL_ALGORITHM_H
 
-#include <gsl/assert> // for Expects
-#include <gsl/span>   // for dynamic_extent, span
+#include "assert" // for Expects
+#include "span"   // for dynamic_extent, span
 
 #include <algorithm>   // for copy_n
 #include <cstddef>     // for ptrdiff_t

include/gsl/gsl

@@ -17,16 +17,16 @@
 #ifndef GSL_GSL_H
 #define GSL_GSL_H
 
-#include <gsl/algorithm>   // copy
-#include <gsl/assert>      // Ensures/Expects
-#include <gsl/byte>        // byte
-#include <gsl/pointers>    // owner, not_null
-#include <gsl/span>        // span
-#include <gsl/string_span> // zstring, string_span, zstring_builder...
-#include <gsl/util>        // finally()/narrow_cast()...
+#include "algorithm"   // copy
+#include "assert"      // Ensures/Expects
+#include "byte"        // byte
+#include "pointers"    // owner, not_null
+#include "span"        // span
+#include "string_span" // zstring, string_span, zstring_builder...
+#include "util"        // finally()/narrow_cast()...
 
 #ifdef __cpp_exceptions
-#include <gsl/narrow> // narrow()
+#include "narrow" // narrow()
 #endif
 
 #endif // GSL_GSL_H

include/gsl/gsl_algorithm

@@ -1,4 +1,4 @@
 #pragma once
 #pragma message(                                                                                   \
     "This header will soon be removed. Use <gsl/algorithm> instead of <gsl/gsl_algorithm>")
-#include <gsl/algorithm>
+#include "algorithm"

include/gsl/gsl_assert

@@ -1,3 +1,3 @@
 #pragma once
 #pragma message("This header will soon be removed. Use <gsl/assert> instead of <gsl/gsl_assert>")
-#include <gsl/assert>
+#include "assert"

include/gsl/gsl_byte

@@ -1,3 +1,3 @@
 #pragma once
 #pragma message("This header will soon be removed. Use <gsl/byte> instead of <gsl/gsl_byte>")
-#include <gsl/byte>
+#include "byte"

include/gsl/gsl_narrow

@@ -1,3 +1,3 @@
 #pragma once
 #pragma message("This header will soon be removed. Use <gsl/narrow> instead of <gsl/gsl_narrow>")
-#include <gsl/narrow>
+#include "narrow"

include/gsl/gsl_util

@@ -1,3 +1,3 @@
 #pragma once
 #pragma message("This header will soon be removed. Use <gsl/util> instead of <gsl/gsl_util>")
-#include <gsl/util>
+#include "util"

include/gsl/narrow

@@ -16,8 +16,9 @@
 
 #ifndef GSL_NARROW_H
 #define GSL_NARROW_H
-#include <gsl/assert> // for Expects
-#include <gsl/util>   // for narrow_cast
+#include "assert"    // for GSL_SUPPRESS
+#include "util"      // for narrow_cast
+#include <exception> // for std::exception
 namespace gsl
 {
 struct narrowing_error : public std::exception
@@ -30,18 +31,34 @@ template <class T, class U, typename std::enable_if<std::is_arithmetic<T>::value
 // clang-format off
 GSL_SUPPRESS(type.1) // NO-FORMAT: attribute
 GSL_SUPPRESS(f.6) // NO-FORMAT: attribute // TODO: MSVC /analyze does not recognise noexcept(false)
+GSL_SUPPRESS(es.46) // NO-FORMAT: attribute // The warning suggests that a floating->unsigned conversion can occur
+                                            // in the static_cast below, and that gsl::narrow should be used instead.
+                                            // Suppress this warning, since gsl::narrow is defined in terms of
+                                            // static_cast
     // clang-format on
     constexpr T narrow(U u) noexcept(false)
 {
     constexpr const bool is_different_signedness =
         (std::is_signed<T>::value != std::is_signed<U>::value);
 
-    const T t = narrow_cast<T>(u);
+GSL_SUPPRESS(es.103) // NO-FORMAT: attribute // don't overflow
+GSL_SUPPRESS(es.104) // NO-FORMAT: attribute // don't underflow
+GSL_SUPPRESS(p.2) // NO-FORMAT: attribute // don't rely on undefined behavior
+    const T t = narrow_cast<T>(u); // While this is technically undefined behavior in some cases (i.e., if the source value is of floating-point type
+                                   // and cannot fit into the destination integral type), the resultant behavior is benign on the platforms
+                                   // that we target (i.e., no hardware trap representations are hit).
 
+#if defined(__clang__) || defined(__GNUC__)
+    #pragma GCC diagnostic push
+    #pragma GCC diagnostic ignored "-Wfloat-equal"
+#endif
     if (static_cast<U>(t) != u || (is_different_signedness && ((t < T{}) != (u < U{}))))
     {
         throw narrowing_error{};
     }
+#if defined(__clang__) || defined(__GNUC__)
+    #pragma GCC diagnostic pop
+#endif
 
     return t;
 }

include/gsl/pointers

@@ -17,7 +17,7 @@
 #ifndef GSL_POINTERS_H
 #define GSL_POINTERS_H
 
-#include <gsl/assert> // for Ensures, Expects
+#include "assert" // for Ensures, Expects
 
 #include <algorithm>    // for forward
 #include <cstddef>      // for ptrdiff_t, nullptr_t, size_t

include/gsl/span

@@ -17,15 +17,20 @@
 #ifndef GSL_SPAN_H
 #define GSL_SPAN_H
 
-#include <gsl/assert> // for Expects
-#include <gsl/byte>   // for byte
-#include <gsl/util>   // for narrow_cast
+#include "assert"   // for Expects
+#include "byte"     // for byte
+#include "span_ext" // for span specialization of gsl::at and other span-related extensions
+#include "util"     // for narrow_cast
 
-#include <array>        // for array
-#include <cstddef>      // for ptrdiff_t, size_t, nullptr_t
-#include <gsl/span_ext> // for span specialization of gsl::at and other span-related extensions
-#include <iterator>     // for reverse_iterator, distance, random_access_...
-#include <type_traits>  // for enable_if_t, declval, is_convertible, inte...
+#include <array>       // for array
+#include <cstddef>     // for ptrdiff_t, size_t, nullptr_t
+#include <iterator>    // for reverse_iterator, distance, random_access_...
+#include <memory>      // for pointer_traits
+#include <type_traits> // for enable_if_t, declval, is_convertible, inte...
+
+#if defined(__has_include) && __has_include(<version>)
+#include <version>
+#endif
 
 #if defined(_MSC_VER) && !defined(__clang__)
 #pragma warning(push)
@@ -110,6 +115,9 @@ namespace details
     class span_iterator
     {
     public:
+#if defined(__cpp_lib_ranges) || (defined(_MSVC_STL_VERSION) && defined(__cpp_lib_concepts))
+        using iterator_concept = std::contiguous_iterator_tag;
+#endif // __cpp_lib_ranges
         using iterator_category = std::random_access_iterator_tag;
         using value_type = std::remove_cv_t<Type>;
         using difference_type = std::ptrdiff_t;
@@ -329,8 +337,26 @@ namespace details
         pointer begin_ = nullptr;
         pointer end_ = nullptr;
         pointer current_ = nullptr;
-    };
 
+        template <typename Ptr>
+        friend struct std::pointer_traits;
+    };
+}} // namespace gsl::details
+
+namespace std
+{
+template <class Type>
+struct pointer_traits<::gsl::details::span_iterator<Type>>
+{
+    using pointer = ::gsl::details::span_iterator<Type>;
+    using element_type = Type;
+    using difference_type = ptrdiff_t;
+
+    static constexpr element_type* to_address(const pointer i) noexcept { return i.current_; }
+};
+} // namespace std
+
+namespace gsl { namespace details {
     template <std::size_t Ext>
     class extent_type
     {
@@ -682,14 +708,11 @@ private:
         template <class OtherExtentType>
         constexpr storage_type(KnownNotNull data, OtherExtentType ext)
             : ExtentType(ext), data_(data.p)
-        {
-            Expects(ExtentType::size() != dynamic_extent);
-        }
+        {}
 
         template <class OtherExtentType>
         constexpr storage_type(pointer data, OtherExtentType ext) : ExtentType(ext), data_(data)
         {
-            Expects(ExtentType::size() != dynamic_extent);
             Expects(data || ExtentType::size() == 0);
         }
 

include/gsl/span_ext

@@ -27,8 +27,8 @@
 //
 ///////////////////////////////////////////////////////////////////////////////
 
-#include <gsl/assert> // GSL_KERNEL_MODE
-#include <gsl/util>   // for narrow_cast, narrow
+#include "assert" // GSL_KERNEL_MODE
+#include "util"   // for narrow_cast, narrow
 
 #include <cstddef> // for ptrdiff_t, size_t
 #include <utility>
@@ -41,7 +41,7 @@ namespace gsl
 {
 
 // [span.views.constants], constants
-constexpr const std::size_t dynamic_extent = narrow_cast<std::size_t>(-1);
+GSL_INLINE constexpr const std::size_t dynamic_extent = narrow_cast<std::size_t>(-1);
 
 template <class ElementType, std::size_t Extent = dynamic_extent>
 class span;

include/gsl/string_span

@@ -17,9 +17,9 @@
 #ifndef GSL_STRING_SPAN_H
 #define GSL_STRING_SPAN_H
 
-#include <gsl/assert>   // for Ensures, Expects
-#include <gsl/span_ext> // for operator!=, operator==, dynamic_extent
-#include <gsl/util>     // for narrow_cast
+#include "assert"   // for Ensures, Expects
+#include "span_ext" // for operator!=, operator==, dynamic_extent
+#include "util"     // for narrow_cast
 
 #include <algorithm> // for equal, lexicographical_compare
 #include <array>     // for array

include/gsl/util

@@ -17,7 +17,7 @@
 #ifndef GSL_UTIL_H
 #define GSL_UTIL_H
 
-#include <gsl/assert> // for Expects
+#include "assert" // for Expects
 
 #include <array>
 #include <cstddef>          // for ptrdiff_t, size_t
@@ -45,6 +45,12 @@
 #define GSL_NODISCARD
 #endif // defined(__cplusplus) && (__cplusplus >= 201703L)
 
+#if defined(__cpp_inline_variables)
+#define GSL_INLINE inline
+#else
+#define GSL_INLINE
+#endif
+
 namespace gsl
 {
 //
@@ -143,10 +149,10 @@ GSL_SUPPRESS(bounds.1) // NO-FORMAT: attribute
 
 #if defined(__cpp_lib_span) && __cpp_lib_span >= 202002L
 template <class T, size_t extent = std::dynamic_extent>
-constexpr auto at(std::span<T, extent> sp, const index i)
+constexpr auto at(std::span<T, extent> sp, const index i) -> decltype(sp[sp.size()])
 {
-    Expects(i >= 0 && i < narrow_cast<i>(sp.size()));
-    return sp[i];
+    Expects(i >= 0 && i < narrow_cast<index>(sp.size()));
+    return sp[gsl::narrow_cast<size_t>(i)];
 }
 #endif // __cpp_lib_span >= 202002L
 } // namespace gsl

pipelines/jobs.yml

@@ -1,26 +1,43 @@
 parameters:
-  jobName: ''
-  imageName: ''
+  CXXVersions: [ 14, 17, 20 ]
+  buildTypes: [ 'Debug', 'Release' ]
+  image: ''
+
+  compiler: ''
+  compilerVersions: ["default"] # if default value, simply uses whatever version is on the machine.
+                                # the text of this default value doesn't actually matter.
+  setupfile: ''
+  extraCmakeArgs: ''
 
 jobs:
-- job:
-  displayName: ${{ parameters.imageName }}
-  pool:
-    vmImage: ${{ parameters.imageName }}
-  strategy:
-    matrix:
-      14_debug:
-        GSL_CXX_STANDARD: '14'
-        BUILD_TYPE: 'Debug'
-      14_release:
-        GSL_CXX_STANDARD: '14'
-        BUILD_TYPE: 'Release'
-      17_debug:
-        GSL_CXX_STANDARD: '17'
-        BUILD_TYPE: 'Debug'
-      17_release:
-        GSL_CXX_STANDARD: '17'
-        BUILD_TYPE: 'Release'
-  continueOnError: false
-  steps:
-  - template: ./steps.yml
+- ${{ each compilerVersion in parameters.compilerVersions }}:
+  - ${{ each CXXVersion in parameters.CXXVersions }}:
+    - ${{ each buildType in parameters.buildTypes }}:
+      - job:
+        displayName: ${{ format('{0} {1} C++{2} {3}', parameters.compiler, compilerVersion, CXXVersion, buildType) }}
+        pool:
+            vmImage: ${{ parameters.image }}
+        continueOnError: false
+
+        steps:
+          - ${{ if not(eq(parameters.setupfile, '')) }}:
+            - template: ${{ parameters.setupfile }}
+              parameters:
+                version: ${{ compilerVersion }}
+
+          - task: CMake@1
+            name: Configure
+            inputs:
+              workingDirectory: build
+              cmakeArgs: '-DGSL_CXX_STANDARD=${{ CXXVersion }} -DCMAKE_BUILD_TYPE=${{ buildType }} -DCI_TESTING:BOOL=ON -DCMAKE_VERBOSE_MAKEFILE:BOOL=ON -Werror=dev ${{ parameters.extraCmakeArgs }} .. '
+
+          - task: CMake@1
+            name: Build
+            inputs:
+              workingDirectory: build
+              cmakeArgs: '--build . '
+
+          - script: ctest . --output-on-failure --no-compress-output
+            name: CTest
+            workingDirectory: build
+            failOnStderr: true

pipelines/setup_apple.yml

@@ -0,0 +1,9 @@
+parameters:
+    version: 0
+
+steps:
+  - script: |
+      if [ "${{ parameters.version }}" != "default" ]; then sudo xcode-select -switch /Applications/Xcode_${{ parameters.version }}.app; fi
+
+    displayName: "Setup Xcode Version"
+    failOnStderr: true

pipelines/setup_clang.yml

@@ -0,0 +1,13 @@
+parameters:
+    version: 0
+
+steps:
+  - script: |
+      echo "##vso[task.setvariable variable=CXX;]${CXX}"
+      echo "##vso[task.setvariable variable=CC;]${CC}"
+
+    displayName: "Setup Clang Version"
+    failOnStderr: true
+    env:
+      CC: clang-${{ parameters.version }}
+      CXX: clang++-${{ parameters.version }}

pipelines/setup_gcc.yml

@@ -0,0 +1,14 @@
+parameters:
+    version: 0
+
+steps:
+  - script: |
+      echo "##vso[task.setvariable variable=CXX;]${CXX}"
+      echo "##vso[task.setvariable variable=CC;]${CC}"
+      if [ "${{ parameters.version }}" = "11" ]; then sudo apt-get install $CXX; fi
+
+    displayName: "Setup GCC Version"
+    failOnStderr: true
+    env:
+      CC: gcc-${{ parameters.version }}
+      CXX: g++-${{ parameters.version }}

pipelines/steps.yml

@@ -1,17 +0,0 @@
-steps:
-  - task: CMake@1
-    name: Configure
-    inputs:
-      workingDirectory: build
-      cmakeArgs: '-DCMAKE_CXX_STANDARD=$(GSL_CXX_STANDARD) -DCMAKE_BUILD_TYPE=$(BUILD_TYPE) -Werror=dev .. '
-
-  - task: CMake@1
-    name: Build
-    inputs:
-      workingDirectory: build
-      cmakeArgs: '--build . '
-
-  - script: ctest . --output-on-failure --no-compress-output
-    name: CTest
-    workingDirectory: build
-    failOnStderr: true

tests/CMakeLists.txt

@@ -9,6 +9,10 @@ include(ExternalProject)
 # will make visual studio generated project group files
 set_property(GLOBAL PROPERTY USE_FOLDERS ON)
 
+if(CI_TESTING AND GSL_CXX_STANDARD EQUAL 20)
+    add_compile_definitions(FORCE_STD_SPAN_TESTS=1)
+endif()
+
 if(IOS)
     add_compile_definitions(GTEST_HAS_DEATH_TEST=1 IOS_PROCESS_DELAY_WORKAROUND=1)
 endif()
@@ -54,10 +58,11 @@ if (CMAKE_CURRENT_SOURCE_DIR STREQUAL CMAKE_SOURCE_DIR)
     find_package(Microsoft.GSL REQUIRED)
 endif()
 
-if (MSVC AND (GSL_CXX_STANDARD EQUAL 17))
+if (MSVC AND (GSL_CXX_STANDARD GREATER_EQUAL 17))
     set(GSL_CPLUSPLUS_OPT -Zc:__cplusplus -permissive-)
 endif()
 
+include(CheckCXXCompilerFlag)
 # this interface adds compile options to how the tests are run
 # please try to keep entries ordered =)
 add_library(gsl_tests_config INTERFACE)
@@ -84,6 +89,7 @@ if(MSVC) # MSVC or simulating MSVC
         >
         $<$<CXX_COMPILER_ID:Clang>:
           -Weverything
+          -Wfloat-equal
           -Wno-c++98-compat
           -Wno-c++98-compat-pedantic
           -Wno-covered-switch-default # GTest
@@ -101,6 +107,10 @@ if(MSVC) # MSVC or simulating MSVC
           >
         >
     )
+    check_cxx_compiler_flag("-Wno-reserved-identifier" WARN_RESERVED_ID)
+    if (WARN_RESERVED_ID)
+        target_compile_options(gsl_tests_config INTERFACE "-Wno-reserved-identifier")
+    endif()
 else()
     target_compile_options(gsl_tests_config INTERFACE
         -fno-strict-aliasing
@@ -113,6 +123,7 @@ else()
         -Wpedantic
         -Wshadow
         -Wsign-conversion
+        -Wfloat-equal
         -Wno-deprecated-declarations # Allow tests for [[deprecated]] elements
         $<$<OR:$<CXX_COMPILER_ID:Clang>,$<CXX_COMPILER_ID:AppleClang>>:
           -Weverything
@@ -135,6 +146,11 @@ else()
           $<$<AND:$<VERSION_GREATER:$<CXX_COMPILER_VERSION>,4.99>,$<VERSION_LESS:$<CXX_COMPILER_VERSION>,6>>:
             $<$<EQUAL:${GSL_CXX_STANDARD},17>:-Wno-undefined-func-template>
           >
+          $<$<AND:$<EQUAL:${GSL_CXX_STANDARD},20>,$<OR:$<CXX_COMPILER_VERSION:11.0.0>,$<CXX_COMPILER_VERSION:10.0.0>>>:
+              -Wno-zero-as-null-pointer-constant  # failing Clang Ubuntu 20.04 tests, seems to be a bug with clang 10.0.0
+                                                  # and clang 11.0.0. (operator< is being re-written by the compiler
+                                                  # as operator<=> and raising the warning)
+          >
         >
         $<$<CXX_COMPILER_ID:AppleClang>:
           $<$<AND:$<VERSION_GREATER:$<CXX_COMPILER_VERSION>,9.1>,$<VERSION_LESS:$<CXX_COMPILER_VERSION>,10>>:
@@ -213,12 +229,17 @@ if(MSVC) # MSVC or simulating MSVC
         >
         $<$<CXX_COMPILER_ID:Clang>:
           -Weverything
+          -Wfloat-equal
           -Wno-c++98-compat
           -Wno-c++98-compat-pedantic
           -Wno-missing-prototypes
           -Wno-unknown-attributes
         >
     )
+    check_cxx_compiler_flag("-Wno-reserved-identifier" WARN_RESERVED_ID)
+    if (WARN_RESERVED_ID)
+        target_compile_options(gsl_tests_config_noexcept INTERFACE "-Wno-reserved-identifier")
+    endif()
 else()
     target_compile_options(gsl_tests_config_noexcept INTERFACE
         -fno-exceptions
@@ -232,6 +253,7 @@ else()
         -Wpedantic
         -Wshadow
         -Wsign-conversion
+        -Wfloat-equal
         $<$<OR:$<CXX_COMPILER_ID:Clang>,$<CXX_COMPILER_ID:AppleClang>>:
           -Weverything
           -Wno-c++98-compat

tests/algorithm_tests.cpp

@@ -27,7 +27,6 @@ namespace gsl
 struct fail_fast;
 } // namespace gsl
 
-using namespace std;
 using namespace gsl;
 
 TEST(algorithm_tests, same_type)
@@ -73,8 +72,8 @@ TEST(algorithm_tests, same_type)
         std::array<int, 5> src{1, 2, 3, 4, 5};
         std::array<int, 10> dst{};
 
-        const span<int> src_span(src);
-        const span<int, 10> dst_span(dst);
+        const gsl::span<int> src_span(src);
+        const gsl::span<int, 10> dst_span(dst);
 
         copy(src_span, dst_span);
         copy(src_span, dst_span.subspan(src_span.size()));

tests/at_tests.cpp

@@ -119,7 +119,7 @@ TEST(at_tests, InitializerList)
     EXPECT_DEATH(gsl::at({1, 2, 3, 4}, 4), expected);
 }
 
-#if defined(__cplusplus) && __cplusplus >= 202002L
+#if defined(FORCE_STD_SPAN_TESTS) || defined(__cpp_lib_span) && __cpp_lib_span >= 202002L
 TEST(at_tests, std_span)
 {
     std::vector<int> vec{1, 2, 3, 4, 5};
@@ -128,18 +128,24 @@ TEST(at_tests, std_span)
     std::vector<int> cvec{1, 2, 3, 4, 5};
     std::span csp{cvec};
 
-    for (size_t i = 0, i < vec.size(); ++i)
+    for (gsl::index i = 0; i < gsl::narrow_cast<gsl::index>(vec.size()); ++i)
     {
-        EXPECT_TRUE(&gsl::at(sp, i) == &vec[i]);
-        EXPECT_TRUE(&gsl::at(csp, i) == &cvec[i]);
+        EXPECT_TRUE(&gsl::at(sp, i) == &vec[gsl::narrow_cast<size_t>(i)]);
+        EXPECT_TRUE(&gsl::at(csp, i) == &cvec[gsl::narrow_cast<size_t>(i)]);
     }
 
+    const auto terminateHandler = std::set_terminate([] {
+        std::cerr << "Expected Death. std_span";
+        std::abort();
+    });
+    const auto expected = GetExpectedDeathString(terminateHandler);
+
     EXPECT_DEATH(gsl::at(sp, -1), expected);
-    EXPECT_DEATH(gsl::at(sp, sp.size()), expected);
+    EXPECT_DEATH(gsl::at(sp, gsl::narrow_cast<gsl::index>(sp.size())), expected);
     EXPECT_DEATH(gsl::at(csp, -1), expected);
-    EXPECT_DEATH(gsl::at(csp, sp.size()), expected);
+    EXPECT_DEATH(gsl::at(csp, gsl::narrow_cast<gsl::index>(sp.size())), expected);
 }
-#endif // __cplusplus >= 202002L
+#endif // defined(FORCE_STD_SPAN_TESTS) || defined(__cpp_lib_span) && __cpp_lib_span >= 202002L
 
 #if !defined(_MSC_VER) || defined(__clang__) || _MSC_VER >= 1910
 static constexpr bool test_constexpr()

tests/span_compatibility_tests.cpp

@@ -55,14 +55,14 @@ void ArrayConvertibilityCheck()
         EXPECT_TRUE(sp_const_nullptr_1.data() == stl_nullptr.data());
         EXPECT_TRUE(sp_const_nullptr_1.size() == 3);
 
-        span<const T* const> sp_const_nullptr_2{std::as_const(stl_nullptr)};
+        gsl::span<const T* const> sp_const_nullptr_2{std::as_const(stl_nullptr)};
         EXPECT_TRUE(sp_const_nullptr_2.data() == stl_nullptr.data());
         EXPECT_TRUE(sp_const_nullptr_2.size() == 3);
 
-        static_assert(std::is_same<decltype(span{stl_nullptr}), span<T*, 3>>::value,
+        static_assert(std::is_same<decltype(gsl::span{stl_nullptr}), gsl::span<T*, 3>>::value,
                       "std::is_same< decltype(span{stl_nullptr}), span<T*, 3>>::value");
         static_assert(
-            std::is_same<decltype(span{std::as_const(stl_nullptr)}), span<T* const, 3>>::value,
+            std::is_same<decltype(gsl::span{std::as_const(stl_nullptr)}), gsl::span<T* const, 3>>::value,
             "std::is_same< decltype(span{std::as_const(stl_nullptr)}), span<T* const, "
             "3>>::value");
     }

tests/span_ext_tests.cpp

@@ -48,7 +48,7 @@ TEST(span_ext_test, make_span_from_pointer_length_constructor)
 
     {
         int* p = nullptr;
-        auto s = make_span(p, narrow_cast<span<int>::size_type>(0));
+        auto s = make_span(p, narrow_cast<gsl::span<int>::size_type>(0));
         EXPECT_TRUE(s.size() == 0);
         EXPECT_TRUE(s.data() == nullptr);
     }
@@ -136,9 +136,9 @@ TEST(span_ext_test, make_span_from_std_array_constructor)
 
     // This test checks for the bug found in gcc 6.1, 6.2, 6.3, 6.4, 6.5 7.1, 7.2, 7.3 - issue #590
     {
-        span<int> s1 = make_span(arr);
+        gsl::span<int> s1 = make_span(arr);
 
-        static span<int> s2;
+        static gsl::span<int> s2;
         s2 = s1;
 
 #if defined(__GNUC__) && __GNUC__ == 6 && (__GNUC_MINOR__ == 4 || __GNUC_MINOR__ == 5) &&          \
@@ -194,7 +194,7 @@ TEST(span_ext_test, make_span_from_container_constructor)
 TEST(span_test, interop_with_gsl_at)
 {
     int arr[5] = {1, 2, 3, 4, 5};
-    span<int> s{arr};
+    gsl::span<int> s{arr};
     EXPECT_TRUE(at(s, 0) == 1);
     EXPECT_TRUE(at(s, 1) == 2);
 }
@@ -202,7 +202,7 @@ TEST(span_test, interop_with_gsl_at)
 TEST(span_ext_test, iterator_free_functions)
 {
     int a[] = {1, 2, 3, 4};
-    span<int> s{a};
+    gsl::span<int> s{a};
 
     EXPECT_TRUE((std::is_same<decltype(s.begin()), decltype(begin(s))>::value));
     EXPECT_TRUE((std::is_same<decltype(s.end()), decltype(end(s))>::value));
@@ -232,7 +232,7 @@ TEST(span_ext_test, iterator_free_functions)
 TEST(span_ext_test, ssize_free_function)
 {
     int a[] = {1, 2, 3, 4};
-    span<int> s{a};
+    gsl::span<int> s{a};
 
     EXPECT_FALSE((std::is_same<decltype(s.size()), decltype(ssize(s))>::value));
     EXPECT_TRUE(s.size() == static_cast<std::size_t>(ssize(s)));
@@ -242,8 +242,8 @@ TEST(span_ext_test, ssize_free_function)
 TEST(span_ext_test, comparison_operators)
 {
     {
-        span<int> s1;
-        span<int> s2;
+        gsl::span<int> s1;
+        gsl::span<int> s2;
         EXPECT_TRUE(s1 == s2);
         EXPECT_FALSE(s1 != s2);
         EXPECT_FALSE(s1 < s2);
@@ -260,8 +260,8 @@ TEST(span_ext_test, comparison_operators)
 
     {
         int arr[] = {2, 1};
-        span<int> s1 = arr;
-        span<int> s2 = arr;
+        gsl::span<int> s1 = arr;
+        gsl::span<int> s2 = arr;
 
         EXPECT_TRUE(s1 == s2);
         EXPECT_FALSE(s1 != s2);
@@ -280,8 +280,8 @@ TEST(span_ext_test, comparison_operators)
     {
         int arr[] = {2, 1}; // bigger
 
-        span<int> s1;
-        span<int> s2 = arr;
+        gsl::span<int> s1;
+        gsl::span<int> s2 = arr;
 
         EXPECT_TRUE(s1 != s2);
         EXPECT_TRUE(s2 != s1);
@@ -300,8 +300,8 @@ TEST(span_ext_test, comparison_operators)
     {
         int arr1[] = {1, 2};
         int arr2[] = {1, 2};
-        span<int> s1 = arr1;
-        span<int> s2 = arr2;
+        gsl::span<int> s1 = arr1;
+        gsl::span<int> s2 = arr2;
 
         EXPECT_TRUE(s1 == s2);
         EXPECT_FALSE(s1 != s2);
@@ -320,8 +320,8 @@ TEST(span_ext_test, comparison_operators)
     {
         int arr[] = {1, 2, 3};
 
-        span<int> s1 = {&arr[0], 2}; // shorter
-        span<int> s2 = arr;          // longer
+        gsl::span<int> s1 = {&arr[0], 2}; // shorter
+        gsl::span<int> s2 = arr;          // longer
 
         EXPECT_TRUE(s1 != s2);
         EXPECT_TRUE(s2 != s1);
@@ -341,8 +341,8 @@ TEST(span_ext_test, comparison_operators)
         int arr1[] = {1, 2}; // smaller
         int arr2[] = {2, 1}; // bigger
 
-        span<int> s1 = arr1;
-        span<int> s2 = arr2;
+        gsl::span<int> s1 = arr1;
+        gsl::span<int> s2 = arr2;
 
         EXPECT_TRUE(s1 != s2);
         EXPECT_TRUE(s2 != s1);

tests/span_tests.cpp

@@ -40,10 +40,12 @@
 #endif // __has_include(<string_view>)
 #endif // __has_include
 #endif // (defined(__cpp_deduction_guides) && (__cpp_deduction_guides >= 201611L))
+#if defined(__cplusplus) && __cplusplus >= 202002L
+#include <span>
+#endif // __cplusplus >= 202002L
 
 #include "deathTestCommon.h"
 
-using namespace std;
 using namespace gsl;
 
 namespace
@@ -1085,7 +1087,7 @@ TEST(span_test, as_bytes)
 
     int b[5] = {1, 2, 3, 4, 5};
     {
-        span<int> sp(begin(b), static_cast<size_t>(-2));
+        span<int> sp(std::begin(b), static_cast<size_t>(-2));
         EXPECT_DEATH((void) sp.size_bytes(), expected);
     }
 }
@@ -1298,3 +1300,20 @@ TEST(span_test, front_back)
     EXPECT_DEATH(s2.front(), expected);
     EXPECT_DEATH(s2.back(), expected);
 }
+
+#if defined(FORCE_STD_SPAN_TESTS) || defined(__cpp_lib_span) && __cpp_lib_span >= 202002L
+TEST(span_test, std_span)
+{
+    // make sure std::span can be constructed from gsl::span
+    int arr[5] = {1, 2, 3, 4, 5};
+    gsl::span<int> gsl_span{arr};
+#if defined(__cpp_lib_ranges) || (defined(_MSVC_STL_VERSION) && defined(__cpp_lib_concepts))
+    EXPECT_TRUE(std::to_address(gsl_span.begin()) == gsl_span.data());
+    EXPECT_TRUE(std::to_address(gsl_span.end()) == gsl_span.data() + gsl_span.size());
+#endif // __cpp_lib_ranges
+
+    std::span<int> std_span = gsl_span;
+    EXPECT_TRUE(std_span.data() == gsl_span.data());
+    EXPECT_TRUE(std_span.size() == gsl_span.size());
+}
+#endif // defined(FORCE_STD_SPAN_TESTS) || defined(__cpp_lib_span) && __cpp_lib_span >= 202002L

tests/string_span_tests.cpp

@@ -30,7 +30,6 @@
 
 #include "deathTestCommon.h"
 
-using namespace std;
 using namespace gsl;
 
 // Generic string functions

tests/utils_tests.cpp

@@ -149,5 +149,7 @@ TEST(utils_tests, narrow)
     EXPECT_TRUE(
         narrow<std::complex<float>>(std::complex<double>(4, 2)) == std::complex<float>(4, 2));
     EXPECT_THROW(narrow<std::complex<float>>(std::complex<double>(4.2)), narrowing_error);
+
+    EXPECT_TRUE(narrow<int>(float(1)) == 1);
 }
 #endif // GSL_KERNEL_MODE