diff --git a/.github/workflows/build.yml b/.github/workflows/build.yml
new file mode 100644
index 0000000..0b1048a
--- /dev/null
+++ b/.github/workflows/build.yml
@@ -0,0 +1,21 @@
+name: Build
+
+on:
+  push:
+  pull_request:
+
+jobs:
+  build:
+    name: Build
+    runs-on: ubuntu-24.04
+    steps:
+      - name: Install dependencies
+        run: |
+          sudo apt-get update
+          sudo apt-get install --assume-yes --no-install-recommends ca-certificates build-essential git googletest libgtest-dev
+      - uses: actions/checkout@v4
+        with:
+          submodules: recursive
+      - name: Build
+        run: |
+          make recsplit ranksel fenwick dynranksel
diff --git a/Makefile b/Makefile
index d38e7d5..62cb4c6 100644
--- a/Makefile
+++ b/Makefile
@@ -1,4 +1,4 @@
-CXXFLAGS = -g -std=c++17 -Wall -Wextra -O0 -march=native -l gtest -I./ -fsanitize=address -fsanitize=undefined
+CXXFLAGS = -g -std=c++20 -Wall -Wextra -O0 -march=native -l gtest -I./ -fsanitize=address -fsanitize=undefined
 
 bin/bits: test/bits/* sux/bits/* sux/util/Vector.hpp sux/support/*
 	@mkdir -p bin
@@ -22,39 +22,39 @@ ALLOC_TYPE?=MALLOC
 
 recsplit: benchmark/function/recsplit_*
 	@mkdir -p bin
-	$(CXX) -std=c++17 -I./ -O3 -DSTATS -march=native -DLEAF=$(LEAF) -DALLOC_TYPE=$(ALLOC_TYPE) benchmark/function/recsplit_dump.cpp -o bin/recsplit_dump_$(LEAF)
-	$(CXX) -std=c++17 -I./ -O3 -DSTATS -march=native -DLEAF=$(LEAF) -DALLOC_TYPE=$(ALLOC_TYPE) benchmark/function/recsplit_dump128.cpp -o bin/recsplit_dump128_$(LEAF)
-	$(CXX) -std=c++17 -I./ -O3 -DSTATS -march=native -DLEAF=$(LEAF) -DALLOC_TYPE=$(ALLOC_TYPE) benchmark/function/recsplit_load.cpp -o bin/recsplit_load_$(LEAF)
-	$(CXX) -std=c++17 -I./ -O3 -DSTATS -march=native -DLEAF=$(LEAF) -DALLOC_TYPE=$(ALLOC_TYPE) benchmark/function/recsplit_load128.cpp -o bin/recsplit_load128_$(LEAF)
+	$(CXX) -std=c++20 -I./ -O3 -DSTATS -march=native -DLEAF=$(LEAF) -DALLOC_TYPE=$(ALLOC_TYPE) benchmark/function/recsplit_dump.cpp -o bin/recsplit_dump_$(LEAF)
+	$(CXX) -std=c++20 -I./ -O3 -DSTATS -march=native -DLEAF=$(LEAF) -DALLOC_TYPE=$(ALLOC_TYPE) benchmark/function/recsplit_dump128.cpp -o bin/recsplit_dump128_$(LEAF)
+	$(CXX) -std=c++20 -I./ -O3 -DSTATS -march=native -DLEAF=$(LEAF) -DALLOC_TYPE=$(ALLOC_TYPE) benchmark/function/recsplit_load.cpp -o bin/recsplit_load_$(LEAF)
+	$(CXX) -std=c++20 -I./ -O3 -DSTATS -march=native -DLEAF=$(LEAF) -DALLOC_TYPE=$(ALLOC_TYPE) benchmark/function/recsplit_load128.cpp -o bin/recsplit_load128_$(LEAF)
 
 ranksel: benchmark/bits/ranksel.cpp
 	@mkdir -p bin
-	$(CXX) -std=c++17 -I./ -O3 -march=native -DCLASS=SimpleSelect -DNORANKTEST -DMAX_LOG2_LONGWORDS_PER_SUBINVENTORY=0 benchmark/bits/ranksel.cpp -o bin/testsimplesel0
-	$(CXX) -std=c++17 -I./ -O3 -march=native -DCLASS=SimpleSelect -DNORANKTEST -DMAX_LOG2_LONGWORDS_PER_SUBINVENTORY=1 benchmark/bits/ranksel.cpp -o bin/testsimplesel1
-	$(CXX) -std=c++17 -I./ -O3 -march=native -DCLASS=SimpleSelect -DNORANKTEST -DMAX_LOG2_LONGWORDS_PER_SUBINVENTORY=2 benchmark/bits/ranksel.cpp -o bin/testsimplesel2
-	$(CXX) -std=c++17 -I./ -O3 -march=native -DCLASS=SimpleSelect -DNORANKTEST -DMAX_LOG2_LONGWORDS_PER_SUBINVENTORY=3 benchmark/bits/ranksel.cpp -o bin/testsimplesel3
-	$(CXX) -std=c++17 -I./ -O3 -march=native -DCLASS=SimpleSelectHalf -DNORANKTEST benchmark/bits/ranksel.cpp -o bin/testsimplehalf
-	$(CXX) -std=c++17 -I./ -O3 -march=native -DCLASS=EliasFano benchmark/bits/ranksel.cpp -o bin/testeliasfano
-	$(CXX) -std=c++17 -I./ -O3 -march=native -DCLASS=Rank9Sel -DNORANKTEST benchmark/bits/ranksel.cpp -o bin/testrank9sel
-	$(CXX) -std=c++17 -I./ -O3 -march=native -DCLASS=Rank9 -DNOSELECTTEST benchmark/bits/ranksel.cpp -o bin/testrank9
+	$(CXX) -std=c++20 -I./ -O3 -march=native -DCLASS=SimpleSelect -DNORANKTEST -DMAX_LOG2_LONGWORDS_PER_SUBINVENTORY=0 benchmark/bits/ranksel.cpp -o bin/testsimplesel0
+	$(CXX) -std=c++20 -I./ -O3 -march=native -DCLASS=SimpleSelect -DNORANKTEST -DMAX_LOG2_LONGWORDS_PER_SUBINVENTORY=1 benchmark/bits/ranksel.cpp -o bin/testsimplesel1
+	$(CXX) -std=c++20 -I./ -O3 -march=native -DCLASS=SimpleSelect -DNORANKTEST -DMAX_LOG2_LONGWORDS_PER_SUBINVENTORY=2 benchmark/bits/ranksel.cpp -o bin/testsimplesel2
+	$(CXX) -std=c++20 -I./ -O3 -march=native -DCLASS=SimpleSelect -DNORANKTEST -DMAX_LOG2_LONGWORDS_PER_SUBINVENTORY=3 benchmark/bits/ranksel.cpp -o bin/testsimplesel3
+	$(CXX) -std=c++20 -I./ -O3 -march=native -DCLASS=SimpleSelectHalf -DNORANKTEST benchmark/bits/ranksel.cpp -o bin/testsimplehalf
+	$(CXX) -std=c++20 -I./ -O3 -march=native -DCLASS=EliasFano benchmark/bits/ranksel.cpp -o bin/testeliasfano
+	$(CXX) -std=c++20 -I./ -O3 -march=native -DCLASS=Rank9Sel -DNORANKTEST benchmark/bits/ranksel.cpp -o bin/testrank9sel
+	$(CXX) -std=c++20 -I./ -O3 -march=native -DCLASS=Rank9 -DNOSELECTTEST benchmark/bits/ranksel.cpp -o bin/testrank9
 
 fenwick: benchmark/util/fenwick.cpp
 	@mkdir -p bin/fenwick
-	$(CXX) -std=c++17 -I./ -O3 -march=native -DSET_BOUND=64 -DSET_ALLOC=MALLOC benchmark/util/fenwick.cpp -o bin/fenwick/malloc_64
-	$(CXX) -std=c++17 -I./ -O3 -march=native -DSET_BOUND=64 -DSET_ALLOC=SMALLPAGE benchmark/util/fenwick.cpp -o bin/fenwick/smallpage_64
-	$(CXX) -std=c++17 -I./ -O3 -march=native -DSET_BOUND=64 -DSET_ALLOC=TRANSHUGEPAGE benchmark/util/fenwick.cpp -o bin/fenwick/transhugepage_64
-	$(CXX) -std=c++17 -I./ -O3 -march=native -DSET_BOUND=64 -DSET_ALLOC=FORCEHUGEPAGE benchmark/util/fenwick.cpp -o bin/fenwick/forcehugepage_64
+	$(CXX) -std=c++20 -I./ -O3 -march=native -DSET_BOUND=64 -DSET_ALLOC=MALLOC benchmark/util/fenwick.cpp -o bin/fenwick/malloc_64
+	$(CXX) -std=c++20 -I./ -O3 -march=native -DSET_BOUND=64 -DSET_ALLOC=SMALLPAGE benchmark/util/fenwick.cpp -o bin/fenwick/smallpage_64
+	$(CXX) -std=c++20 -I./ -O3 -march=native -DSET_BOUND=64 -DSET_ALLOC=TRANSHUGEPAGE benchmark/util/fenwick.cpp -o bin/fenwick/transhugepage_64
+	$(CXX) -std=c++20 -I./ -O3 -march=native -DSET_BOUND=64 -DSET_ALLOC=FORCEHUGEPAGE benchmark/util/fenwick.cpp -o bin/fenwick/forcehugepage_64
 
 dynranksel: benchmark/bits/dynranksel.cpp
 	@mkdir -p bin/dynranksel
-	g++ -std=c++17 -I./ -O3 -march=native -DSET_ALLOC=MALLOC benchmark/bits/dynranksel.cpp -o bin/dynranksel/malloc_1
-	g++ -std=c++17 -I./ -O3 -march=native -DSET_ALLOC=SMALLPAGE benchmark/bits/dynranksel.cpp -o bin/dynranksel/smallpage_1
-	g++ -std=c++17 -I./ -O3 -march=native -DSET_ALLOC=TRANSHUGEPAGE benchmark/bits/dynranksel.cpp -o bin/dynranksel/transhugepage_1
-	g++ -std=c++17 -I./ -O3 -march=native -DSET_ALLOC=FORCEHUGEPAGE benchmark/bits/dynranksel.cpp -o bin/dynranksel/forcehugepage_1
-	g++ -std=c++17 -I./ -O3 -march=native -DSET_STRIDE=16 -DSET_ALLOC=MALLOC benchmark/bits/dynranksel.cpp -o bin/dynranksel/malloc_16
-	g++ -std=c++17 -I./ -O3 -march=native -DSET_STRIDE=16 -DSET_ALLOC=SMALLPAGE benchmark/bits/dynranksel.cpp -o bin/dynranksel/smallpage_16
-	g++ -std=c++17 -I./ -O3 -march=native -DSET_STRIDE=16 -DSET_ALLOC=TRANSHUGEPAGE benchmark/bits/dynranksel.cpp -o bin/dynranksel/transhugepage_16
-	g++ -std=c++17 -I./ -O3 -march=native -DSET_STRIDE=16 -DSET_ALLOC=FORCEHUGEPAGE benchmark/bits/dynranksel.cpp -o bin/dynranksel/forcehugepage_16
+	g++ -std=c++20 -I./ -O3 -march=native -DSET_ALLOC=MALLOC benchmark/bits/dynranksel.cpp -o bin/dynranksel/malloc_1
+	g++ -std=c++20 -I./ -O3 -march=native -DSET_ALLOC=SMALLPAGE benchmark/bits/dynranksel.cpp -o bin/dynranksel/smallpage_1
+	g++ -std=c++20 -I./ -O3 -march=native -DSET_ALLOC=TRANSHUGEPAGE benchmark/bits/dynranksel.cpp -o bin/dynranksel/transhugepage_1
+	g++ -std=c++20 -I./ -O3 -march=native -DSET_ALLOC=FORCEHUGEPAGE benchmark/bits/dynranksel.cpp -o bin/dynranksel/forcehugepage_1
+	g++ -std=c++20 -I./ -O3 -march=native -DSET_STRIDE=16 -DSET_ALLOC=MALLOC benchmark/bits/dynranksel.cpp -o bin/dynranksel/malloc_16
+	g++ -std=c++20 -I./ -O3 -march=native -DSET_STRIDE=16 -DSET_ALLOC=SMALLPAGE benchmark/bits/dynranksel.cpp -o bin/dynranksel/smallpage_16
+	g++ -std=c++20 -I./ -O3 -march=native -DSET_STRIDE=16 -DSET_ALLOC=TRANSHUGEPAGE benchmark/bits/dynranksel.cpp -o bin/dynranksel/transhugepage_16
+	g++ -std=c++20 -I./ -O3 -march=native -DSET_STRIDE=16 -DSET_ALLOC=FORCEHUGEPAGE benchmark/bits/dynranksel.cpp -o bin/dynranksel/forcehugepage_16
 
 .PHONY: clean
 
diff --git a/sux/function/RecSplit.hpp b/sux/function/RecSplit.hpp
index ccf42c2..4c0a58b 100644
--- a/sux/function/RecSplit.hpp
+++ b/sux/function/RecSplit.hpp
@@ -39,6 +39,7 @@
 #include <fstream>
 #include <string>
 #include <vector>
+#include <span>
 
 namespace sux::function {