Export assert_fail with FMT_API. This fixes dll build.
diff --git a/include/fmt/core.h b/include/fmt/core.h
index d49f36e..80e87e2 100644
--- a/include/fmt/core.h
+++ b/include/fmt/core.h
@@ -229,7 +229,7 @@
// A workaround for gcc 4.8 to make void_t work in a SFINAE context.
template <typename... Ts> struct void_t_impl { using type = void; };
-void assert_fail(const char* file, int line, const char* message);
+FMT_API void assert_fail(const char* file, int line, const char* message);
#ifndef FMT_ASSERT
# ifdef NDEBUG
diff --git a/include/fmt/format-inl.h b/include/fmt/format-inl.h
index 72b3046..21caeec 100644
--- a/include/fmt/format-inl.h
+++ b/include/fmt/format-inl.h
@@ -55,7 +55,7 @@
FMT_BEGIN_NAMESPACE
namespace internal {
-FMT_FUNC void assert_fail(const char* file, int line, const char* message) {
+FMT_API FMT_FUNC void assert_fail(const char* file, int line, const char* message) {
print(stderr, "{}:{}: assertion failed: {}", file, line, message);
std::abort();
}