apply workarounds for (probably bogus) warnings or errors from nvcc

src/fmt/base.h

@@ -480,11 +480,23 @@ constexpr FMT_ALWAYS_INLINE const char* narrow(const char* s) { return s; }
 template <typename Char>
 FMT_CONSTEXPR auto compare(const Char* s1, const Char* s2, std::size_t n)
     -> int {
+  // LAMMPS customization. Try to suppress warnings from nvcc
+#if 0  // original code
   if (!is_constant_evaluated() && sizeof(Char) == 1) return memcmp(s1, s2, n);
   for (; n != 0; ++s1, ++s2, --n) {
     if (*s1 < *s2) return -1;
     if (*s1 > *s2) return 1;
   }
+#else
+  if (!is_constant_evaluated() && sizeof(Char) == 1) {
+    return memcmp(s1, s2, n);
+  } else {
+    for (; n != 0; ++s1, ++s2, --n) {
+      if (*s1 < *s2) return -1;
+      if (*s1 > *s2) return 1;
+    }
+  }
+#endif
   return 0;
 }
 

src/fmt/format.h

@@ -2591,7 +2591,9 @@ class bigint {
   }
 
  public:
-  FMT_CONSTEXPR bigint() : exp_(0) {}
+  // LAMMPS customization. NVCC wrongly complains about calling a non-constepr function
+  // so we comment out constexpr here for now.
+  /* FMT_CONSTEXPR */ bigint() : exp_(0) {}
   explicit bigint(uint64_t n) { assign(n); }
 
   bigint(const bigint&) = delete;