Merge bitcoin#11071: Use static_assert(…, …) (C++11) instead of assert(…) where appropriate

d1e6f91 Prefer compile-time checking over run-time checking (practicalswift)

Pull request description:

  Use `static_assert(…, …)` instead of `assert(…)` where appropriate.

Tree-SHA512: 63b6e50916bcef2195a73f93476bd69657ed9a8eea0bc4382933f478a6df639632c23c076df401fea648142adcb308bb2e6be35cc3dabca30daf7649b790f436

Author: laanwj

doc/developer-notes.md

@@ -37,6 +37,7 @@ code.
 
 - **Miscellaneous**
   - `++i` is preferred over `i++`.
+  - `static_assert` is preferred over `assert` where possible. Generally; compile-time checking is preferred over run-time checking.
   - Align pointers and references to the left i.e. use `type& var` and not `type &var`.
 
 Block style example:

src/arith_uint256.h

@@ -250,7 +250,7 @@ class base_uint
 
     uint64_t GetLow64() const
     {
-        assert(WIDTH >= 2);
+        static_assert(WIDTH >= 2, "Assertion WIDTH >= 2 failed (WIDTH = BITS / 32). BITS is a template parameter.");
         return pn[0] | (uint64_t)pn[1] << 32;
     }
 };