Merge pull request #5882 from YosysHQ/std_cpp20

Bump required standard to C++20

.github/workflows/test-compile.yml

@@ -44,18 +44,18 @@ jobs:
           - ubuntu-latest
         compiler:
           # oldest supported
-          - 'clang-10'
+          - 'clang-14'
-          - 'gcc-10'
+          - 'gcc-11'
           # newest, make sure to update maximum standard step to match
-          - 'clang-19'
+          - 'clang-22'
-          - 'gcc-14'
+          - 'gcc-15'
         include:
           # macOS x86
           - os: macos-15-intel
-            compiler: 'clang-19'
+            compiler: 'clang-22'
           # macOS arm
           - os: macos-latest
-            compiler: 'clang-19'
+            compiler: 'clang-22'
       fail-fast: false
     steps:
       - name: Checkout Yosys
@@ -74,6 +74,7 @@ jobs:
         uses: aminya/setup-cpp@v1
         with:
           compiler: ${{ matrix.compiler }}
+          gcc: ${{ (matrix.os == 'ubuntu-latest' && matrix.compiler == 'clang-14') && '12' || '' }}
 
       - name: Tool versions
         shell: bash
@@ -81,21 +82,26 @@ jobs:
           $CC --version
           $CXX --version
 
-      # minimum standard
+      - name: Fix clang-14 toolchain
-      - name: Build C++17
+        if: matrix.os == 'ubuntu-latest' && matrix.compiler == 'clang-14'
-        shell: bash
         run: |
-          make config-$CC_SHORT
+          echo 'CXXFLAGS=--gcc-toolchain=/usr -isystem /usr/include/c++/12 -isystem /usr/include/x86_64-linux-gnu/c++/12' >> $GITHUB_ENV
-          make -j$procs CXXSTD=c++17 compile-only
 
-      # maximum standard, only on newest compilers
+      # minimum standard
       - 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: ${{ matrix.compiler == 'clang-22' || matrix.compiler == 'gcc-15' }}
+        shell: bash
+        run: |
+          make config-$CC_SHORT
+          make -j$procs CXXSTD=c++26 compile-only
+
   test-compile-result:
     runs-on: ubuntu-latest
     needs:

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)

docs/source/getting_started/installation.rst

@@ -87,7 +87,7 @@ not regularly tested:
 Build prerequisites
 ^^^^^^^^^^^^^^^^^^^
 
-A C++ compiler with C++17 support is required as well as some standard tools
+A C++ compiler with C++20 support is required as well as some standard tools
 such as GNU Flex, GNU Bison (>=3.8), Make, and Python (>=3.11). Some additional
 tools: readline, libffi, Tcl and zlib; are optional but enabled by default (see
 :makevar:`ENABLE_*` settings in Makefile). Graphviz and Xdot are used by the

docs/source/yosys_internals/extending_yosys/contributing.rst

@@ -286,7 +286,7 @@ have incorrect results in unusual situations.
 Coding style
 ~~~~~~~~~~~~
 
-Yosys is written in C++17.
+Yosys is written in C++20.
 
 In general Yosys uses ``int`` instead of ``size_t``. To avoid compiler warnings
 for implicit type casts, always use ``GetSize(foobar)`` instead of

docs/source/yosys_internals/index.rst

@@ -25,7 +25,7 @@ wide range of real-world designs, including the `OpenRISC 1200 CPU`_, the
 
 .. _k68 CPU: http://opencores.org/projects/k68
 
-Yosys is written in C++, targeting C++17 at minimum. This chapter describes some
+Yosys is written in C++, targeting C++20 at minimum. This chapter describes some
 of the fundamental Yosys data structures. For the sake of simplicity the C++
 type names used in the Yosys implementation are used in this chapter, even
 though the chapter only explains the conceptual idea behind it and can be used

kernel/fmt.cc

@@ -804,8 +804,10 @@ std::string Fmt::render() const
 								buf += 'X';
 							else if (has_z)
 								buf += 'Z';
-							else
+							else {
-								buf += (part.hex_upper ? "0123456789ABCDEF" : "0123456789abcdef")[subvalue.as_int()];
+								const char *digits = part.hex_upper ? "0123456789ABCDEF" : "0123456789abcdef";
+								buf += digits[subvalue.as_int()];
+							}
 						}
 					} else if (part.base == 10) {
 						if (part.show_base)

kernel/io.h

@@ -475,7 +475,8 @@ public:
 private:
 	std::string_view fmt;
 	bool has_escapes = false;
-	FoundFormatSpec specs[sizeof...(Args)] = {};
+	// Making array at least size of one to make MSVC happy and strict to standards 
+	FoundFormatSpec specs[sizeof...(Args) ? sizeof...(Args) : 1] = {};
 };
 
 template <typename T> struct WrapType { using type = T; };

kernel/yosys_common.h

@@ -120,10 +120,10 @@
 #  define YS_MAYBE_UNUSED
 #endif
 
-#if __cplusplus >= 201703L
+#if __cplusplus >= 202002L
 #  define YS_FALLTHROUGH [[fallthrough]];
 #else
-#  error "C++17 or later compatible compiler is required"
+#  error "C++20 or later compatible compiler is required"
 #endif
 
 #if defined(__has_cpp_attribute) && __has_cpp_attribute(gnu::cold)

misc/create_vcxsrc.sh

@@ -25,6 +25,7 @@ if [ -f "/usr/include/FlexLexer.h" ] ; then
 	cp /usr/include/FlexLexer.h libs/flex/FlexLexer.h
 	ls libs/flex/*.h >> ../../srcfiles.txt
 fi
+sed -i '\#libs/../kernel/yosys.h#d' ../../srcfiles.txt
 
 popd
 {
@@ -35,7 +36,7 @@ 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

passes/cmds/timeest.cc

@@ -100,7 +100,7 @@ struct EstimateSta {
 								cell, cell->type.unescape());
 					continue;
 				}
-				if (ff.sig_clk != clk)
+				if (!clk || ff.sig_clk.as_bit() != *clk)
 					continue;
 				launch.append(ff.sig_q);
 				sample.append(ff.sig_d);
@@ -144,12 +144,12 @@ struct EstimateSta {
 					log_error("Unsupported async memory port '%s'\n", rd.cell);
 					continue;
 				}
-				if (sigmap(rd.clk) != clk)
+				if (!clk || sigmap(rd.clk).as_bit() != *clk)
 					continue;
 				add_seq(rd.cell, rd.data, {rd.addr, rd.srst, rd.en});
 			}
 			for (auto &wr : mem.wr_ports) {
-				if (sigmap(wr.clk) != clk)
+				if (!clk || sigmap(wr.clk).as_bit() != *clk)
 					continue;
 				add_seq(wr.cell, {}, {wr.en, wr.addr, wr.data});
 			}

passes/sat/formalff.cc

@@ -767,7 +767,7 @@ struct FormalFfPass : public Pass {
 							ff.sig_d = ff.sig_ad;
 						}
 
-						if (!ff.has_clk || sigmap(ff.sig_clk) != gate_clock || ff.pol_clk != pol_clk) {
+						if (!ff.has_clk || sigmap(ff.sig_clk).as_bit() != gate_clock || ff.pol_clk != pol_clk) {
 							log_debug("FF driver for gate enable %s.%s of gated clk bit %s.%s has incompatible clocking: "
 								  "%s %s.%s\n",
 								  module, log_signal(SigSpec(gate_enable)), module,
@@ -798,7 +798,7 @@ struct FormalFfPass : public Pass {
 								auto &mem = memories.at(clocked_cell->name);
 								bool changed = false;
 								for (auto &rd_port : mem.rd_ports) {
-									if (rd_port.clk_enable && rd_port.clk == clk && rd_port.clk_polarity == pol_clk) {
+									if (rd_port.clk_enable && rd_port.clk.as_bit() == clk && rd_port.clk_polarity == pol_clk) {
 										log_debug("patching rd port\n");
 										changed = true;
 										rd_port.clk = gate_clock;
@@ -808,7 +808,7 @@ struct FormalFfPass : public Pass {
 									}
 								}
 								for (auto &wr_port : mem.wr_ports) {
-									if (wr_port.clk_enable && wr_port.clk == clk && wr_port.clk_polarity == pol_clk) {
+									if (wr_port.clk_enable && wr_port.clk.as_bit() == clk && wr_port.clk_polarity == pol_clk) {
 										log_debug("patching wr port\n");
 										changed = true;
 										wr_port.clk = gate_clock;

pyosys/generator.py

@@ -376,7 +376,7 @@ class PyosysWrapperGenerator(object):
     def make_preprocessor_options(self):
         py_include = get_paths()["include"]
         preprocessor_bin = shutil.which("clang++") or "g++"
-        cxx_std = os.getenv("CXX_STD", "c++17")
+        cxx_std = os.getenv("CXX_STD", "c++20")
         return ParserOptions(
             preprocessor=make_gcc_preprocessor(
                 defines=["_YOSYS_", "YOSYS_ENABLE_PYTHON"],

tests/functional/test_functional.py

@@ -21,7 +21,7 @@ def yosys(script):
     run([base_path / 'yosys', '-Q', '-p', script])
 
 def compile_cpp(in_path, out_path, args):
-    run(['g++', '-g', '-std=c++17'] + args + [str(in_path), '-o', str(out_path)])
+    run(['g++', '-g', '-std=c++20'] + args + [str(in_path), '-o', str(out_path)])
 
 def yosys_synth(verilog_file, rtlil_file):
     yosys(f"read_verilog {quote(verilog_file)} ; prep ; setundef -undriven -undef ; write_rtlil {quote(rtlil_file)}")