build!: Move to C++17 minimum (AcademySoftwareFoundation#4199)

These are build-breaking changes that impose a variety of new minimum
dependencies for the toolchain.

C++17 is the new minimum. All hail C++17.

Bump minimum compiler versions to the respective releases of each one
that is requred to fully support C++17 for us. This means new minimum
changes of gcc 6.1 -> 9.3, clang 3.4 -> 5.0, icc 17 -> 19, and MSVS
v19.14 or higher now.

Remove CI tests for too-old platforms, and adjust some others that
needed particular components upgraded. We now will no longer attempt to
test on "VFX Platform 2019" or 2020. The 2021 platforms are the earliest
we claim to support (reflecting VFXP's guidance about trying to support
up to 3 years back).

By removing the old test cases, we're also removing the last platforms
that test Python 2.7. So while this PR isn't the one that officially
removes the last vestiges of Python 2, it does mean that once this is
merged, we will no longer be testing less than Python 3.7. (A separate
PR removing all Python 2 support will follow and presumably be merged
around the same time.)

With C++17 min, remove traces of boost::filesystem. We can rely on
std::filesystem now.

Clean up pre-C++17 macros in platform.h

Needless to say, this will not be backported to any release branches,
which guarantee that they will never raise the minimum supported
versions of any dependencies. This is just for future OIIO. I won't
merge this until after April 1, at which point I will also tag the last
spot in master that is known to work with C++14/gcc6.

Signed-off-by: Larry Gritz <[email protected]>

.github/workflows/ci.yml

@@ -34,29 +34,6 @@ jobs:
       fail-fast: false
       matrix:
         include:
-          - desc: gcc6/C++14 py2.7 boost1.66 exr2.4 ocio1.1
-            nametag: linux-vfx2019
-            runner: ubuntu-latest
-            container: aswf/ci-osl:2019
-            vfxyear: 2019
-            cxx_std: 14
-            openexr_ver: v2.4.3
-            python_ver: 2.7
-            simd: sse4.2
-            fmt_ver: 7.0.1
-            pybind11_ver: v2.4.2
-            setenvs: export PUGIXML_VERSION=v1.9 CMAKE_VERSION=3.15.5
-          - desc: gcc6/C++14 py3.7 boost1.70 exr2.4 ocio1.1
-            nametag: linux-vfx2020
-            runner: ubuntu-latest
-            container: aswf/ci-osl:2020
-            vfxyear: 2020
-            cxx_std: 14
-            python_ver: 3.7
-            simd: avx
-            fmt_ver: 7.0.1
-            pybind11_ver: v2.5.0
-            setenvs: export PUGIXML_VERSION=v1.9 WEBP_VERSION=v1.1.0
           - desc: gcc9/C++17 py3.7 boost1.73 exr2.5 ocio2.0
             nametag: linux-vfx2021
             runner: ubuntu-latest
@@ -68,14 +45,14 @@ jobs:
             fmt_ver: 7.1.0
             pybind11_ver: v2.7.0
             setenvs: export PUGIXML_VERSION=v1.9 WEBP_VERSION=v1.1.0
-          - desc: clang10/C++14 avx2 exr2.5 ocio2.0
+          - desc: clang10/C++17 avx2 exr2.5 ocio2.0
             nametag: linux-clang10-cpp14
             runner: ubuntu-latest
             container: aswf/ci-osl:2021-clang10
             vfxyear: 2021
             cc_compiler: clang
             cxx_compiler: clang++
-            cxx_std: 14
+            cxx_std: 17
             pybind11_ver: v2.6.2
             python_ver: 3.7
             simd: "avx2,f16c"
@@ -163,18 +140,18 @@ jobs:
             simd: "avx2,f16c"
             fmt_ver: 10.1.1
             pybind11_ver: v2.10.0
-          - desc: oldest/hobbled gcc6.3/C++14 py2.7 boost-1.66 exr-2.4 no-sse no-ocio
+          - desc: oldest/hobbled gcc9.3/C++17 py3.7 boost-1.66 exr-2.4 no-sse no-ocio
             # Oldest versions of the dependencies that we can muster, and various
             # things disabled (no SSE, OCIO, or OpenCV, don't embed plugins).
             nametag: linux-oldest
             runner: ubuntu-latest
-            container: aswf/ci-osl:2019
-            vfxyear: 2019
-            cxx_std: 14
+            container: aswf/ci-osl:2021
+            vfxyear: 2021
+            cxx_std: 17
             fmt_ver: 7.0.1
             openexr_ver: v2.4.0
             pybind11_ver: v2.4.2
-            python_ver: 2.7
+            python_ver: 3.7
             simd: 0
             setenvs: export  EMBEDPLUGINS=0
                              CMAKE_VERSION=3.15.5
@@ -352,13 +329,13 @@ jobs:
                             OPENCOLORIO_VERSION=v2.1.2
                             USE_OPENVDB=0
                             # The installed OpenVDB has a TLS conflict with Python 3.8
-          - desc: debug gcc7/C++14, sse4.2, exr2.4
-            nametag: linux-gcc7-cpp14-debug
+          - desc: debug gcc9/C++17, sse4.2, exr2.4
+            nametag: linux-gcc9-cpp17-debug
             runner: ubuntu-20.04
             container:
               image: ubuntu-18.04
-            cxx_compiler: g++-7
-            cxx_std: 14
+            cxx_compiler: g++-9
+            cxx_std: 17
             python_ver: 2.7
             simd: sse4.2
             openexr_ver: v2.4.3
@@ -367,25 +344,13 @@ jobs:
                             PUGIXML_VERSION=v1.9
                             CTEST_TEST_TIMEOUT=1200
 
-          - desc: gcc8 C++17 avx exr2.5
-            nametag: linux-gcc8
-            runner: ubuntu-20.04
-            container:
-              image: ubuntu-18.04
-            cc_compiler: gcc-8
-            cxx_compiler: g++-8
-            cxx_std: 17
-            openexr_ver: v2.5.8
-            pybind11_ver: v2.5.0
-            simd: avx
-            setenvs: export EXTRA_DEP_PACKAGES=libjpeg-turbo8-dev
-          - desc: static libs gcc7 C++14 exr2.4
+          - desc: static libs gcc9 C++17 exr2.4
             nametag: linux-static
             runner: ubuntu-20.04
             container:
               image: ubuntu-18.04
-            cxx_compiler: g++-7
-            cxx_std: 14
+            cxx_compiler: g++-9
+            cxx_std: 17
             openexr_ver: v2.4.3
             pybind11_ver: v2.6.2
             setenvs: export BUILD_SHARED_LIBS=OFF

INSTALL.md

@@ -14,12 +14,11 @@ NEW or CHANGED MINIMUM dependencies since the last major release are **bold**.
 
 ### Required dependencies -- OIIO will not build at all without these
 
- * C++14 or higher (also builds with C++17, and C++20)
+ * **C++17 or higher** (also builds with C++20)
      * The default build mode is C++17. This can be controlled by via the
-       CMake configuration flag: `-DCMAKE_CXX_STANDARD=14`, etc.
-     * ADVISORY: We expect that OIIO 2.6 in 2024 will require C++17 or higher.
- * Compilers: gcc 6.1 - 13.1, clang 3.4 - 17, MSVS 2017 - 2019,
-   Intel icc 17+, Intel OneAPI C++ compiler 2022+.
+       CMake configuration flag: `-DCMAKE_CXX_STANDARD=20`, etc.
+ * Compilers: **gcc 9.3** - 13.1, **clang 5** - 17, MSVS 2017 - 2019 (**v19.14
+   and up**), **Intel icc 19+**, Intel OneAPI C++ compiler 2022+.
  * **CMake >= 3.15** (tested through 3.28)
  * **OpenEXR/Imath >= 2.4** (recommended: 3.1 or higher; tested through 3.2
    and main) (ADVISORY: We expect that OIIO 2.6 in 2024 will require OpenEXR >= 3.1)

Makefile

@@ -356,7 +356,7 @@ help:
 	@echo "      VERBOSE=1                Show all compilation commands"
 	@echo "      STOP_ON_WARNING=0        Do not stop building if compiler warns"
 	@echo "      MYCC=xx MYCXX=yy         Use custom compilers"
-	@echo "      CMAKE_CXX_STANDARD=14    C++ standard to build with (default is 17)"
+	@echo "      CMAKE_CXX_STANDARD=20    C++ standard to build with (default is 17)"
 	@echo "      USE_LIBCPLUSPLUS=1       For clang, use libc++"
 	@echo "      GLIBCXX_USE_CXX11_ABI=1  For gcc, use the new string ABI"
 	@echo "      EXTRA_CPP_ARGS=          Additional args to the C++ command"

src/build-scripts/ci-startup.bash

@@ -37,7 +37,7 @@ export OpenImageIO_CI=true
 export USE_NINJA=${USE_NINJA:=1}
 export CMAKE_GENERATOR=${CMAKE_GENERATOR:=Ninja}
 export CMAKE_BUILD_TYPE=${CMAKE_BUILD_TYPE:=Release}
-export CMAKE_CXX_STANDARD=${CMAKE_CXX_STANDARD:=14}
+export CMAKE_CXX_STANDARD=${CMAKE_CXX_STANDARD:=17}
 
 export LOCAL_DEPS_DIR=${LOCAL_DEPS_DIR:=$HOME/ext}
 export PATH=${LOCAL_DEPS_DIR}/dist/bin:$PATH

src/build-scripts/gh-installdeps.bash

@@ -118,20 +118,16 @@ else
 
     export CMAKE_PREFIX_PATH=/usr/lib/x86_64-linux-gnu:$CMAKE_PREFIX_PATH
 
-    if [[ "$CXX" == "g++-6" ]] ; then
-        time sudo apt-get install -y g++-6
-    elif [[ "$CXX" == "g++-7" ]] ; then
-        time sudo apt-get install -y g++-7
-    elif [[ "$CXX" == "g++-8" ]] ; then
-        time sudo apt-get install -y g++-8
-    elif [[ "$CXX" == "g++-9" ]] ; then
+    if [[ "$CXX" == "g++-9" ]] ; then
         time sudo apt-get install -y g++-9
     elif [[ "$CXX" == "g++-10" ]] ; then
         time sudo apt-get install -y g++-10
     elif [[ "$CXX" == "g++-11" ]] ; then
         time sudo apt-get install -y g++-11
     elif [[ "$CXX" == "g++-12" ]] ; then
         time sudo apt-get install -y g++-12
+    elif [[ "$CXX" == "g++-13" ]] ; then
+        time sudo apt-get install -y g++-13
     fi
 
     if [[ "$CXX" == "icpc" || "$CC" == "icc" || "$USE_ICC" != "" || "$USE_ICX" != "" ]] ; then

src/cmake/compiler.cmake

@@ -48,10 +48,10 @@ endmacro ()
 ###########################################################################
 # C++ language standard
 #
-set (CMAKE_CXX_MINIMUM 14)
+set (CMAKE_CXX_MINIMUM 17)
 set (CMAKE_CXX_STANDARD 17 CACHE STRING
      "C++ standard to build with (14, 17, 20, etc.) Minimum is ${CMAKE_CXX_MINIMUM}.")
-set (DOWNSTREAM_CXX_STANDARD 14 CACHE STRING
+set (DOWNSTREAM_CXX_STANDARD 17 CACHE STRING
      "C++ minimum standard to impose on downstream clients")
 set (CMAKE_CXX_STANDARD_REQUIRED ON)
 set (CMAKE_CXX_EXTENSIONS OFF)
@@ -389,29 +389,6 @@ if (NOT MSVC AND NOT APPLE AND NOT ANDROID)
 endif ()
 
 
-###########################################################################
-# Check if we need have std::filesystem on this platform.
-#
-cmake_push_check_state ()
-set (CMAKE_REQUIRED_DEFINITIONS ${CSTD_FLAGS})
-check_cxx_source_compiles("#include <filesystem>
-      int main() { std::filesystem::path p; return 0; }"
-      USE_STD_FILESYSTEM)
-if (USE_STD_FILESYSTEM AND GCC_VERSION AND GCC_VERSION VERSION_LESS 9.0)
-    message (STATUS "Excluding USE_STD_FILESYSTEM because gcc is ${GCC_VERSION}")
-    set (USE_STD_FILESYSTEM OFF)
-endif ()
-if (USE_STD_FILESYSTEM)
-    # Note: std::filesystem seems unreliable for gcc until 9
-    message (STATUS "Compiler supports std::filesystem")
-    proj_add_compile_definitions (-DUSE_STD_FILESYSTEM)
-else ()
-    message (STATUS "Using Boost::filesystem")
-    proj_add_compile_definitions (-DUSE_BOOST_FILESYSTEM)
-endif ()
-cmake_pop_check_state ()
-
-
 ###########################################################################
 # Code coverage options
 #

src/cmake/externalpackages.cmake

@@ -53,9 +53,6 @@ if (MSVC)
 endif ()
 
 set (Boost_COMPONENTS thread)
-if (NOT USE_STD_FILESYSTEM)
-    list (APPEND Boost_COMPONENTS filesystem)
-endif ()
 message (STATUS "Boost_COMPONENTS = ${Boost_COMPONENTS}")
 # The FindBoost.cmake interface is broken if it uses boost's installed
 # cmake output (e.g. boost 1.70.0, cmake <= 3.14). Specifically it fails
@@ -232,8 +229,8 @@ if (LibRaw_FOUND AND LibRaw_VERSION VERSION_LESS 0.20 AND CMAKE_CXX_STANDARD VER
     # Currently, we issue the above warning and let them take their chances.
     # If we wish to disable the LibRaw<0.20/C++17 combination that may fail,
     # just uncomment the following two lines.
-    # set (LibRaw_FOUND 0)
-    # set (LIBRAW_FOUND 0)
+    set (LibRaw_FOUND 0)
+    set (LIBRAW_FOUND 0)
 endif ()
 
 checked_find_package (OpenJPEG VERSION_MIN 2.0

src/doc/Doxyfile

@@ -2164,7 +2164,6 @@ PREDEFINED             = DOXYGEN_SHOULD_SKIP_THIS \
                          OIIO_HOSTDEVICE= \
                          OIIO_NAMESPACE_BEGIN="namespace OIIO {" \
                          OIIO_NAMESPACE_END="}" \
-                         OIIO_CONSTEXPR14=constexpr \
                          OIIO_CONSTEXPR17=constexpr \
                          OIIO_CONSTEXPR20=constexpr \
                          OIIO_INLINE_CONSTEXPR="inline constexpr" \

src/include/OpenImageIO/detail/farmhash.h

@@ -83,19 +83,13 @@
 // Make static inline 'const expr, if possible.  Also, try to make CUDA friendly
 // for device code.
 #undef STATIC_INLINE
-#if OIIO_CPLUSPLUS_VERSION >= 14
-#  define HASH_CAN_USE_CONSTEXPR 1
-#endif
-#define STATIC_INLINE OIIO_HOSTDEVICE inline OIIO_CONSTEXPR14
+#define HASH_CAN_USE_CONSTEXPR 1
+#define STATIC_INLINE OIIO_HOSTDEVICE inline constexpr
 
 // FARMHASH PORTABILITY LAYER: Runtime error if misconfigured
 
 #ifndef FARMHASH_DIE_IF_MISCONFIGURED
-#ifdef HASH_CAN_USE_CONSTEXPR
 #define FARMHASH_DIE_IF_MISCONFIGURED
-#else
-#define FARMHASH_DIE_IF_MISCONFIGURED do { *(char*)(len % 17) = 0; } while (0)
-#endif
 #endif
 
 // FARMHASH PORTABILITY LAYER: endianness and byteswapping functions

src/include/OpenImageIO/oiioversion.h.in

@@ -185,7 +185,7 @@ namespace @PROJ_NAME@ = @PROJ_NAMESPACE_V@;
 #define OIIO_USING_IMATH_VERSION_MAJOR @Imath_VERSION_MAJOR@
 #define OIIO_USING_IMATH_VERSION_MINOR @Imath_VERSION_MINOR@
 
-// Which CPP standard (11, 14, etc.) was this copy of OIIO *built* with?
+// Which CPP standard (17, 20, etc.) was this copy of OIIO *built* with?
 #define OIIO_BUILD_CPP @CMAKE_CXX_STANDARD@
 
 // DEPRECATED(2.1): old macros separately giving compatibility.

src/include/OpenImageIO/platform.h

@@ -64,7 +64,7 @@
 // OIIO_INLINE_CONSTEXPR : inline constexpr variables, added in C++17. For
 //                         older C++, static constexpr.
 //
-// Note: oiioversion.h defines OIIO_BUILD_CPP (set to 14, 17, etc.)
+// Note: oiioversion.h defines OIIO_BUILD_CPP (set to 17, 20, etc.)
 // reflecting what OIIO itself was *built* with.  In contrast,
 // OIIO_CPLUSPLUS_VERSION defined below will be set to the right number for
 // the C++ standard being compiled RIGHT NOW. These two things may be the
@@ -77,18 +77,13 @@
 #    define OIIO_CONSTEXPR17 constexpr
 #    define OIIO_CONSTEXPR20 constexpr
 #    define OIIO_INLINE_CONSTEXPR inline constexpr
-#elif (__cplusplus >= 201703L)
+#elif (__cplusplus >= 201703L) || (defined(_MSC_VER) && _MSC_VER >= 1914)
 #    define OIIO_CPLUSPLUS_VERSION 17
 #    define OIIO_CONSTEXPR17 constexpr
 #    define OIIO_CONSTEXPR20 /* not constexpr before C++20 */
 #    define OIIO_INLINE_CONSTEXPR inline constexpr
-#elif (__cplusplus >= 201402L) || (defined(_MSC_VER) && _MSC_VER >= 1914)
-#    define OIIO_CPLUSPLUS_VERSION 14
-#    define OIIO_CONSTEXPR17 /* not constexpr before C++17 */
-#    define OIIO_CONSTEXPR20 /* not constexpr before C++20 */
-#    define OIIO_INLINE_CONSTEXPR static constexpr
 #else
-#    error "This version of OIIO is meant to work only with C++14 and above"
+#    error "This version of OIIO is meant to work only with C++17 and above"
 #endif
 
 // DEPRECATED(2.3): use C++14 constexpr
@@ -113,12 +108,6 @@
 #    define __has_attribute(x) 0
 #endif
 
-// In C++17 (and some compilers before that), __has_include("blah.h") or
-// __has_include(<blah.h>) can test for presence of an include file.
-#ifndef __has_include
-#    define __has_include(x) 0
-#endif
-
 
 
 // Detect which compiler and version we're using
@@ -389,7 +378,7 @@
 #endif
 
 
-// OIIO_FORCELINE is a function attribute that attempts to make the function
+// OIIO_FORCEINLINE is a function attribute that attempts to make the function
 // always inline. On many compilers regular 'inline' is only advisory. Put
 // this attribute before the function return type, just like you would use
 // 'inline'.
@@ -431,15 +420,11 @@
 #    define OIIO_CONST_FUNC
 #endif
 
-// OIIO_MAYBE_UNUSED is a function or variable attribute that assures the
-// compiler that it's fine for the item to appear to be unused.
-#if OIIO_CPLUSPLUS_VERSION >= 17 || __has_cpp_attribute(maybe_unused)
-#    define OIIO_MAYBE_UNUSED [[maybe_unused]]
-#elif defined(__GNUC__) || defined(__clang__) || defined(__INTEL_COMPILER) || __has_attribute(unused)
-#    define OIIO_MAYBE_UNUSED __attribute__((unused))
-#else
-#    define OIIO_MAYBE_UNUSED
-#endif
+// OIIO_MAYBE_UNUSED is an annotator for function or variable attribute that
+// assures the compiler that it's fine for the item to appear to be unused.
+// Consider this deprecated (as of OIIO 3.0), you should favor C++17's
+// [[maybe_unused]] attribute.
+#define OIIO_MAYBE_UNUSED [[maybe_unused]]
 
 // DEPRECATED(1.9) name:
 #define OIIO_UNUSED_OK OIIO_MAYBE_UNUSED
@@ -455,26 +440,18 @@
 
 
 // OIIO_DEPRECATED before a function declaration marks it as deprecated in
-// a way that will generate compile warnings if it is called.
-#if OIIO_CPLUSPLUS_VERSION >= 14 || __has_cpp_attribute(deprecated)
-#    define OIIO_DEPRECATED(msg) [[deprecated(msg)]]
-#elif defined(__GNUC__) || defined(__clang__) || __has_attribute(deprecated)
-#    define OIIO_DEPRECATED(msg) __attribute__((deprecated(msg)))
-#elif defined(_MSC_VER)
-#    define OIIO_DEPRECATED(msg) __declspec(deprecated(msg))
-#else
-#    define OIIO_DEPRECATED(msg)
-#endif
+// a way that will generate compile warnings if it is called. This should
+// itself be considered deprecated (as of OIIO 3.0) and code should use
+// [[deprecated(msg)]] instead.
+#define OIIO_DEPRECATED(msg) [[deprecated(msg)]]
 
 
 // OIIO_FALLTHROUGH at the end of a `case` label's statements documents that
 // the switch statement case is intentionally falling through to the code
 // for the next case.
-#if OIIO_CPLUSPLUS_VERSION >= 17 || __has_cpp_attribute(fallthrough)
-#    define OIIO_FALLTHROUGH [[fallthrough]]
-#else
-#    define OIIO_FALLTHROUGH
-#endif
+// Consider this deprecated (as of OIIO 3.0), you should favor C++17's
+// [[fallthrough]] attribute.
+#define OIIO_FALLTHROUGH [[fallthrough]]
 
 
 // OIIO_NODISCARD following a function declaration documents that the