From b2e8ae3a39ec83ebfb8610e2a523c439a91538ac Mon Sep 17 00:00:00 2001
From: Gregor Gorjanc <gregor.gorjanc@gmail.com>
Date: Mon, 9 Feb 2026 07:04:41 +0000
Subject: [PATCH] Setting C++20 as standard to fix CRAN windows issue Fixes #63

---
 RcppTskit/src/Makevars.in | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/RcppTskit/src/Makevars.in b/RcppTskit/src/Makevars.in
index e1e33d0..e96d7a0 100644
--- a/RcppTskit/src/Makevars.in
+++ b/RcppTskit/src/Makevars.in
@@ -59,6 +59,9 @@ RCPPTSKIT_LDFLAGS =
 PKG_CFLAGS = $(RCPPTSKIT_CFLAGS)
 PKG_CXXFLAGS = $(RCPPTSKIT_CXXFLAGS)
 
+# core.h:__tsk_nan_f requires C++20 on CRAN/Windows, but see #63
+CXX_STD = CXX20
+
 # Explicit compile rule for tskit C files
 tskit/%.o: tskit/%.c
 	$(CC) $(ALL_CPPFLAGS) $(PKG_CFLAGS) $(CFLAGS) $(CPICFLAGS) -c $< -o $@