clean up "static" and "constexpr" types

- use `static constexpr inline' to avoid requiring
  explicit declarations in object code
- use `const Foo* const' to maybe put into readonly
  binary segment (at least for ELF DSOs)
- `constexpr' in function scope has storage, avoid
  `static'
- don't use `constexpr' where there's no advantage,
  like arrays

We'd like to avoid overhead of atomic initialization
for each function call. No idea how `static constexpr'
requiring storage in the standard plays with atomic
initialization requirement. Hearsay points that
`constexpr' without `static' in block scope behaves
more to our liking. It's all hazy though.

I'm not 100% sure if `static inline constexpr' has any
storage. Hopefully none, like a #define, and stuff
bigger than registers gets coalesced within the same
module, with small stuff being immediates.

1 files changed, 2 insertions, 1 deletions

diff --git a/spline/spline.hpp b/spline/spline.hpp
index 0d080cef..a3532855 100644
--- a/spline/spline.hpp
+++ b/spline/spline.hpp
@@ -16,6 +16,7 @@ using namespace options;
 
 #include "export.hpp"
 
+#include <cstddef>
 #include <vector>
 #include <limits>
 #include <memory>
@@ -102,7 +103,7 @@ class OTR_SPLINE_EXPORT spline : public base_spline
     std::shared_ptr<spline_detail::settings> s;
     QMetaObject::Connection connection, conn_maxx, conn_maxy;
 
-    static constexpr std::size_t value_count = 4096;
+    static constexpr inline std::size_t value_count = 4096;
 
     std::vector<float> data = std::vector<float>(value_count, float(-16));