From 141a2e36389795b3e6e9cae82c8639843446c4db Mon Sep 17 00:00:00 2001
From: Miodrag Milanovic <mmicko@gmail.com>
Date: Mon, 17 Jun 2024 16:55:36 +0200
Subject: [PATCH] Make C++17 compiler required

---
 .github/workflows/test-compile.yml | 4 ++--
 Makefile                           | 4 ++--
 kernel/yosys_common.h              | 6 +-----
 3 files changed, 5 insertions(+), 9 deletions(-)

diff --git a/.github/workflows/test-compile.yml b/.github/workflows/test-compile.yml
index 375ea7fc5..a892c91ce 100644
--- a/.github/workflows/test-compile.yml
+++ b/.github/workflows/test-compile.yml
@@ -64,11 +64,11 @@ jobs:
           $CXX --version
 
       # minimum standard
-      - name: Build C++11
+      - name: Build C++17
         shell: bash
         run: |
           make config-$CC_SHORT
-          make -j$procs CXXSTD=c++11 compile-only
+          make -j$procs CXXSTD=c++17 compile-only
 
       # maximum standard, only on newest compilers
       - name: Build C++20
diff --git a/Makefile b/Makefile
index 7760cec43..73ea0bcc1 100644
--- a/Makefile
+++ b/Makefile
@@ -90,7 +90,7 @@ all: top-all
 YOSYS_SRC := $(dir $(firstword $(MAKEFILE_LIST)))
 VPATH := $(YOSYS_SRC)
 
-CXXSTD ?= c++11
+CXXSTD ?= c++17
 CXXFLAGS := $(CXXFLAGS) -Wall -Wextra -ggdb -I. -I"$(YOSYS_SRC)" -MD -MP -D_YOSYS_ -fPIC -I$(PREFIX)/include
 LIBS := $(LIBS) -lstdc++ -lm
 PLUGIN_LINKFLAGS :=
@@ -1015,7 +1015,7 @@ qtcreator:
 vcxsrc: $(GENFILES) $(EXTRA_TARGETS)
 	rm -rf yosys-win32-vcxsrc-$(YOSYS_VER){,.zip}
 	set -e; for f in `ls $(filter %.cc %.cpp,$(GENFILES)) $(addsuffix .cc,$(basename $(OBJS))) $(addsuffix .cpp,$(basename $(OBJS))) 2> /dev/null`; do \
-		echo "Analyse: $$f" >&2; cpp -std=c++11 -MM -I. -D_YOSYS_ $$f; done | sed 's,.*:,,; s,//*,/,g; s,/[^/]*/\.\./,/,g; y, \\,\n\n,;' | grep '^[^/]' | sort -u | grep -v kernel/version_ > srcfiles.txt
+		echo "Analyse: $$f" >&2; cpp -std=c++17 -MM -I. -D_YOSYS_ $$f; done | sed 's,.*:,,; s,//*,/,g; s,/[^/]*/\.\./,/,g; y, \\,\n\n,;' | grep '^[^/]' | sort -u | grep -v kernel/version_ > srcfiles.txt
 	bash misc/create_vcxsrc.sh yosys-win32-vcxsrc $(YOSYS_VER) $(GIT_REV)
 	echo "namespace Yosys { extern const char *yosys_version_str; const char *yosys_version_str=\"Yosys (Version Information Unavailable)\"; }" > kernel/version.cc
 	zip yosys-win32-vcxsrc-$(YOSYS_VER)/genfiles.zip $(GENFILES) kernel/version.cc
diff --git a/kernel/yosys_common.h b/kernel/yosys_common.h
index 9f1bc2f58..56d2356b1 100644
--- a/kernel/yosys_common.h
+++ b/kernel/yosys_common.h
@@ -142,12 +142,8 @@ extern Tcl_Obj *Tcl_ObjSetVar2(Tcl_Interp *interp, Tcl_Obj *part1Ptr, Tcl_Obj *p
 
 #if __cplusplus >= 201703L
 #  define YS_FALLTHROUGH [[fallthrough]];
-#elif defined(__clang__)
-#  define YS_FALLTHROUGH [[clang::fallthrough]];
-#elif defined(__GNUC__)
-#  define YS_FALLTHROUGH [[gnu::fallthrough]];
 #else
-#  define YS_FALLTHROUGH
+#  error "C++17 or later compatible compiler is required"
 #endif