Update build configuration to C++20 (see #3611)

BUILD.gn

@@ -17,10 +17,10 @@
 #
 #      > set GN_DEFINES=is_official_build=true
 #
-#    Example B: Generate VS2017 project files in addition to the default Ninja
+#    Example B: Generate VS2022 project files in addition to the default Ninja
 #               build files on Windows:
 #
-#      > set GN_ARGUMENTS=--ide=vs2017 --sln=cef --filters=//cef/*
+#      > set GN_ARGUMENTS=--ide=vs2022 --sln=cef --filters=//cef/*
 #
 #      After completing the "GN Automated Build" or "GN Manual Build" section
 #      open "out\<build_dir>\cef.sln" for editing and debugging. Building must
@@ -1232,15 +1232,15 @@ config("libcef_dll_wrapper_config") {
   # avoid accidental usage of new/unsupported language features in sample apps.
   # For Chromium defaults see //build/config/compiler/BUILD.gn.
   #
-  # Mixing C++17 and C++20 leads to build errors with modules enabled. Dependent
+  # Mixing C++20 and C++23 leads to build errors with modules enabled. Dependent
   # targets must therefore also set use_libcxx_modules = false (see issue #3611).
   if (is_win) {
-    cflags_cc = [ "/std:c++17" ]
+    cflags_cc = [ "/std:c++20" ]
   } else {
-    cflags_cc = [ "-std=c++17" ]
+    cflags_cc = [ "-std=c++20" ]
   }
   if (is_mac) {
-    cflags_objcc = [ "-std=c++17" ]
+    cflags_objcc = [ "-std=c++20" ]
   }
 
   if (cef_api_version != "") {

bazel/library_helpers.bzl

@@ -62,24 +62,24 @@ def declare_cc_library(copts=[], local_defines=[], **kwargs):
         **kwargs
     )
 
-def declare_objc_library(copts=[], enable_cxx17=True, **kwargs):
+def declare_objc_library(copts=[], enable_cxx20=True, **kwargs):
     """
     objc_library wrapper that applies common copts.
 
     Args:
         copts: Additional compiler options to add.
-        enable_cxx17: If True (default), adds -std=c++17 for Objective-C++ (.mm) files.
+        enable_cxx20: If True (default), adds -std=c++20 for Objective-C++ (.mm) files.
                      Set to False for pure Objective-C (.m) files that should not use C++ standard.
         **kwargs: Additional arguments passed to objc_library.
     """
     # NOTE: objc_library does not support local_defines on MacOS, so on
     # that platform we put the defines in copts instead.
 
-    # Add C++17 standard for Objective-C++ files on macOS (default behavior)
+    # Add C++20 standard for Objective-C++ files on macOS (default behavior)
     # This allows .mm files to properly parse C++ headers while allowing
     # pure .m files to opt out when needed.
     cxx_standard = select({
-        "@platforms//os:macos": ["-std=c++17"] if enable_cxx17 else [],
+        "@platforms//os:macos": ["-std=c++20"] if enable_cxx20 else [],
         "//conditions:default": [],
     })
 

cmake/cef_variables.cmake.in

@@ -115,7 +115,7 @@ if(OS_LINUX)
     -fno-rtti                       # Disable real-time type information
     -fno-threadsafe-statics         # Don't generate thread-safe statics
     -fvisibility-inlines-hidden     # Give hidden visibility to inlined class member functions
-    -std=c++17                      # Use the C++17 language standard
+    -std=c++20                      # Use the C++20 language standard
     -Wsign-compare                  # Warn about mixed signed/unsigned type comparisons
     )
   list(APPEND CEF_COMPILER_FLAGS_DEBUG
@@ -287,7 +287,7 @@ if(OS_MAC)
     -fno-threadsafe-statics         # Don't generate thread-safe statics
     -fobjc-call-cxx-cdtors          # Call the constructor/destructor of C++ instance variables in ObjC objects
     -fvisibility-inlines-hidden     # Give hidden visibility to inlined class member functions
-    -std=c++17                      # Use the C++17 language standard
+    -std=c++20                      # Use the C++20 language standard
     -Wno-narrowing                  # Don't warn about type narrowing
     -Wsign-compare                  # Warn about mixed signed/unsigned type comparisons
     )
@@ -427,7 +427,7 @@ if(OS_WINDOWS)
     /GF           # Enable string pooling
     )
   list(APPEND CEF_CXX_COMPILER_FLAGS
-    /std:c++17    # Use the C++17 language standard
+    /std:c++20    # Use the C++20 language standard
     )
   list(APPEND CEF_LINKER_FLAGS_DEBUG
     /DEBUG        # Generate debug information

tests/cefsimple_capi/CMakeLists.txt.in

@@ -67,7 +67,7 @@ if(OS_WINDOWS)
   # Remove C++ standard flag since this is a C-only target.
   # The Visual Studio generator sets both <LanguageStandard> and <LanguageStandard_C>
   # properties, and <LanguageStandard> takes precedence when compiling C files.
-  list(REMOVE_ITEM CEF_CXX_COMPILER_FLAGS "/std:c++17")
+  list(REMOVE_ITEM CEF_CXX_COMPILER_FLAGS "/std:c++20")
 endif()
 
 

tools/distrib/bazel/.bazelrc

@@ -12,11 +12,11 @@ build --enable_platform_specific_config
 # Common configuration.
 #
 
-# Build with C++17.
-# See also the enable_cxx17 argument to declare_objc_library()
-build:linux --cxxopt='-std=c++17'
-build:macos --cxxopt='-std=c++17'
-build:windows --cxxopt='/std:c++17'
+# Build with C++20.
+# See also the enable_cxx20 argument to declare_objc_library()
+build:linux --cxxopt='-std=c++20'
+build:macos --cxxopt='-std=c++20'
+build:windows --cxxopt='/std:c++20'
 
 #
 # Windows configuration.

tools/distrib/bazel/tests-cefsimple_capi-BUILD.bazel.in

@@ -60,7 +60,7 @@ declare_cc_library(
 declare_objc_library(
     name = "BrowserLibMac_ObjC",
     srcs = srcs_browser_mac,  # .m files
-    enable_cxx17 = False,  # Pure Objective-C, not Objective-C++
+    enable_cxx20 = False,  # Pure Objective-C, not Objective-C++
     target_compatible_with = [
         "@platforms//os:macos",
     ],