Linker error when compiling with clang-cl: undefined symbol: __udivti3

[Kingcom]

This is very likely to be the fault of Clang, but perhaps something can be done to work around it.

I'm using the official Windows build of LLVM 10.0.0 from a Visual Studio 2017 x64 environment. Calling any formatting function (even something trivial like fmt::print("");) results in the linker error above. This seems to be because Clang mishandles 128 bit integers and incorrectly generates a call to a function not implemented by the Microsoft runtime.

I was able to work around the issue with the following patch:

diff --git a/include/fmt/format.h b/include/fmt/format.h
index 336d2c67..5e5b87dd 100644
--- a/include/fmt/format.h
+++ b/include/fmt/format.h
@@ -759,8 +759,7 @@ using uint32_or_64_or_128_t =
 // represent all values of T.
 template <typename T>
 using uint32_or_64_or_128_t = conditional_t<
-    num_bits<T>() <= 32, uint32_t,
-    conditional_t<num_bits<T>() <= 64, uint64_t, uint128_t>>;
+    num_bits<T>() <= 32, uint32_t, uint64_t>;
 #endif

I've tried defining FMT_REDUCE_INT_INSTANTIATIONS to 1, but with that it fails to compile due to an ambiguous call:

..\ext\fmt\include\fmt/format-inl.h(639,5): error: call to member function 'multiply' is ambiguous
    multiply(uint32_or_64_or_128_t<Int>(value));
    ^~~~~~~~
..\ext\fmt\include\fmt/format-inl.h(566,8): note: candidate function
  void multiply(uint32_t value) {
       ^
..\ext\fmt\include\fmt/format-inl.h(577,8): note: candidate function
  void multiply(uint64_t value) {

[vitaut]

That's a clang issue but a PR with a workaround would be welcome.