FMT_NOEXCEPT should not depend on FMT_EXCEPTIONS

[qis]

As the title suggests, FMT_NOEXCEPT should not depend on FMT_EXCEPTIONS.

This will allow std::is_nothrow_* traits to detect the actual behavior properly and things like std::move_if_noexcept to work the same way in both, normal and -fno-exceptions builds.

diff --git i/include/fmt/core.h w/include/fmt/core.h
index 1303f55..96a98f9 100644
--- i/include/fmt/core.h
+++ w/include/fmt/core.h
@@ -131,11 +131,7 @@
 #endif

 #ifndef FMT_NOEXCEPT
-# if FMT_EXCEPTIONS
 #  define FMT_NOEXCEPT FMT_DETECTED_NOEXCEPT
-# else
-#  define FMT_NOEXCEPT
-# endif
 #endif

 // This is needed because GCC still uses throw() in its headers when exceptions

[EricWF]

FMT_DETECTED_NOEXCEPT is sometimes defined to throw(). I don't think you want to add throw() when exceptions are disabled but noexcept is not available (If only because noexcept traits and metaprogramming are only available when noexcept is).

[qis]

@EricWF So the default FMT_NOEXCEPT value should also depend on noexcept support?

diff --git i/include/fmt/core.h w/include/fmt/core.h
index 1303f55..5488934 100644
--- i/include/fmt/core.h
+++ w/include/fmt/core.h
@@ -126,12 +126,14 @@
     (FMT_GCC_VERSION >= 408 && FMT_HAS_GXX_CXX11) || \
     FMT_MSC_VER >= 1900
 # define FMT_DETECTED_NOEXCEPT noexcept
+# define FMT_HAS_NOEXCEPT 1
 #else
 # define FMT_DETECTED_NOEXCEPT throw()
+# define FMT_HAS_NOEXCEPT 0
 #endif

 #ifndef FMT_NOEXCEPT
-# if FMT_EXCEPTIONS
+# if FMT_EXCEPTIONS || FMT_FMT_HAS_NOEXCEPT
 #  define FMT_NOEXCEPT FMT_DETECTED_NOEXCEPT
 # else
 #  define FMT_NOEXCEPT

[vitaut]

Could you submit a PR?