Node 8: Compiler warning about invalid format passed to fprintf when building in VS 2015

[KobyBo]

• Version: 8.0.0
• Platform: Visual Studio 2015 (Update 3) on Windows 10
• Subsystem: Win32 (x86)
• Using the sln and vcxproj files generated by running "vcbuild.bat x86 release".

Hi
While compiling node v8 (using sources downloaded yesterday) on VS 2015 (Update 3), I've noticed I'm receiving the following compiler warnings:

warning C4476: 'fprintf' : unknown type field character ''' in format specifier
warning C4474: 'fprintf' : too many arguments passed for format string

about the following line in env-inl.h (got the warnings repeatedly, for each cpp which includes env-inl.h):

inline bool Environment::AsyncHooks::pop_ids(double async_id) {
...
    fprintf(stderr,
              "Error: async hook stack has become corrupted ("
              "actual: %'.f, expected: %'.f)\n",
               uid_fields_[kCurrentAsyncId],
               async_id);
..,

The "%'.f" format doesn't seem right (or I'm missing something).

[AndreasMadsen]

Thanks for the report.

It is only supported by some compilers, we are fixing it in #13447