py/objfloat: Workaround non-constant NAN definition on Windows MSVC.

projectgus · dpgeorge · commit 564ef28ad2ca · 2024-11-28T23:56:21.000+11:00
Recent MSVC versions have changed the definition of NAN to a non-constant expression! This is a bug, C standard says it should be a constant. Good explanation and workaround at: https://stackoverflow.com/a/79199887 This work was funded through GitHub Sponsors. Signed-off-by: Angus Gratton <angus@redyak.com.au>
diff --git a/py/objfloat.c b/py/objfloat.c
@@ -47,6 +47,13 @@
 #define M_PI (3.14159265358979323846)
 #endif
 
+// Workaround a bug in recent MSVC where NAN is no longer constant.
+// (By redefining back to the previous MSVC definition of NAN)
+#if defined(_MSC_VER) && _MSC_VER >= 1942
+#undef NAN
+#define NAN (-(float)(((float)(1e+300 * 1e+300)) * 0.0F))
+#endif
+
 typedef struct _mp_obj_float_t {
     mp_obj_base_t base;
     mp_float_t value;
