From 6ff6f8fb3c7c8075a10bec1034176b44e0cc07c0 Mon Sep 17 00:00:00 2001
From: Miodrag Milanovic <mmicko@gmail.com>
Date: Wed, 13 May 2026 10:10:59 +0200
Subject: [PATCH] Bump required standard to C++20

---
 .github/workflows/test-compile.yml | 16 ++++++++--------
 Makefile                           |  4 ++--
 misc/create_vcxsrc.sh              |  2 +-
 3 files changed, 11 insertions(+), 11 deletions(-)

diff --git a/.github/workflows/test-compile.yml b/.github/workflows/test-compile.yml
index 9c75784bf..c322c25b2 100644
--- a/.github/workflows/test-compile.yml
+++ b/.github/workflows/test-compile.yml
@@ -82,20 +82,20 @@ jobs:
           $CXX --version
 
       # minimum standard
-      - name: Build C++17
-        shell: bash
-        run: |
-          make config-$CC_SHORT
-          make -j$procs CXXSTD=c++17 compile-only
-
-      # maximum standard, only on newest compilers
       - name: Build C++20
-        if: ${{ matrix.compiler == 'clang-19' || matrix.compiler == 'gcc-14' }}
         shell: bash
         run: |
           make config-$CC_SHORT
           make -j$procs CXXSTD=c++20 compile-only
 
+      # maximum standard, only on newest compilers
+      - name: Build C++26
+        if: ${{ matrix.compiler == 'clang-19' || matrix.compiler == 'gcc-14' }}
+        shell: bash
+        run: |
+          make config-$CC_SHORT
+          make -j$procs CXXSTD=c++26 compile-only
+
   test-compile-result:
     runs-on: ubuntu-latest
     needs:
diff --git a/Makefile b/Makefile
index 3c5c10cda..afbc11005 100644
--- a/Makefile
+++ b/Makefile
@@ -103,7 +103,7 @@ VPATH := $(YOSYS_SRC)
 # Unit test
 UNITESTPATH := $(YOSYS_SRC)/tests/unit
 
-export CXXSTD ?= c++17
+export CXXSTD ?= c++20
 CXXFLAGS := $(CXXFLAGS) -Wall -Wextra -Werror=unused -ggdb -I. -I"$(YOSYS_SRC)" -MD -MP -D_YOSYS_ -fPIC -I$(PREFIX)/include
 LIBS := $(LIBS) -lstdc++ -lm
 PLUGIN_LINKFLAGS :=
@@ -1142,7 +1142,7 @@ vcxsrc: $(GENFILES) $(EXTRA_TARGETS) kernel/version_$(GIT_REV).cc
 	rm -rf $(VCX_DIR_NAME){,.zip}
 	cp -f kernel/version_$(GIT_REV).cc kernel/version.cc
 	set -e; for f in `ls $(filter %.cc %.cpp,$(GENFILES)) $(addsuffix .cc,$(basename $(OBJS))) $(addsuffix .cpp,$(basename $(OBJS))) 2> /dev/null`; do \
-		echo "Analyse: $$f" >&2; cpp -std=c++17 -MM -I. -D_YOSYS_ $$f; done | sed 's,.*:,,; s,//*,/,g; s,/[^/]*/\.\./,/,g; y, \\,\n\n,;' | grep '^[^/]' | sort -u | grep -v kernel/version_ > srcfiles.txt
+		echo "Analyse: $$f" >&2; cpp -std=c++20 -MM -I. -D_YOSYS_ $$f; done | sed 's,.*:,,; s,//*,/,g; s,/[^/]*/\.\./,/,g; y, \\,\n\n,;' | grep '^[^/]' | sort -u | grep -v kernel/version_ > srcfiles.txt
 	echo "libs/fst/fst_win_unistd.h" >> srcfiles.txt
 	echo "kernel/version.cc" >> srcfiles.txt
 	bash misc/create_vcxsrc.sh $(VCX_DIR_NAME) $(YOSYS_VER)
diff --git a/misc/create_vcxsrc.sh b/misc/create_vcxsrc.sh
index 98c1817bd..c880c2a48 100644
--- a/misc/create_vcxsrc.sh
+++ b/misc/create_vcxsrc.sh
@@ -35,7 +35,7 @@ popd
 	tail -n +$((n+1)) "$vcxsrc"/YosysVS/YosysVS.vcxproj
 } > "$vcxsrc"/YosysVS/YosysVS.vcxproj.new
 
-sed -i 's,</AdditionalIncludeDirectories>,</AdditionalIncludeDirectories>\n      <LanguageStandard>stdcpp17</LanguageStandard>\n      <AdditionalOptions>/Zc:__cplusplus %(AdditionalOptions)</AdditionalOptions>,g' "$vcxsrc"/YosysVS/YosysVS.vcxproj.new
+sed -i 's,</AdditionalIncludeDirectories>,</AdditionalIncludeDirectories>\n      <LanguageStandard>stdcpp20</LanguageStandard>\n      <AdditionalOptions>/Zc:__cplusplus %(AdditionalOptions)</AdditionalOptions>,g' "$vcxsrc"/YosysVS/YosysVS.vcxproj.new
 sed -i 's,<PreprocessorDefinitions>,<PreprocessorDefinitions>YOSYS_ENABLE_THREADS;,g' "$vcxsrc"/YosysVS/YosysVS.vcxproj.new
 if [ -f "/usr/include/FlexLexer.h" ] ; then
 	sed -i 's,</AdditionalIncludeDirectories>,;..\\yosys\\libs\\flex</AdditionalIncludeDirectories>,g' "$vcxsrc"/YosysVS/YosysVS.vcxproj.new