Re: [PATCH] hash_readwrite_autotest: fix printf parameters

[Bruce Richardson <bruce.richardson@intel.com>]

On Fri, Mar 07, 2025 at 02:34:01PM -0800, Andre Muezerie wrote:
> On Fri, Mar 07, 2025 at 09:01:28AM +0000, Bruce Richardson wrote:
> > On Thu, Mar 06, 2025 at 12:03:28PM -0800, Andre Muezerie wrote:
> > > Compiling with MSVC logs the warnings below, which result in
> > > build error:
> > > 
> > > ../app/test/test_hash_readwrite.c(73): warning C4476: 'printf' :
> > >     unknown type field character ''' in format specifier
> > > ../app/test/test_hash_readwrite.c(75): warning C4474: 'printf' :
> > >     too many arguments passed for format string
> > > ../app/test/test_hash_readwrite.c(75): note: placeholders and
> > >     their parameters expect 2 variadic arguments, but 4 were provided
> > > 
> > > Signed-off-by: Andre Muezerie <andremue@linux.microsoft.com>
> > > ---
> > >  app/test/test_hash_readwrite.c | 2 +-
> > >  1 file changed, 1 insertion(+), 1 deletion(-)
> > > 
> > IF the "'" character is not supported, is there some other method to do
> > thousands grouping in MSVC?
> > 
> > /Bruce
> 
> The problem exists with all compilers I tried on Windows:
> 
> 1) MSVC logs the error I mentioned above
> 
> 2) GCC and Clang don't complain at compile time, but don't honor the "'" as a special
> character. As an example,
> printf("%'d\n", 1024);
> results in
> 'd 
> 
> It seems that for this syntax to work as you would expect, support needs to exist in both the
> compiler and the libraries used.
> 
> Back to your question: there's no equivalent syntax on Windows that provides the thousands grouping.
> If really needed (and I understand it is useful for large numbers), we could get the same result
> by calling a helper function that would convert the number in the formatted string and use that
> in the printf statement.
> 
> There is a Win32 API that does that. It takes a string as input though: GetNumberFormatA.
> (https://learn.microsoft.com/en-us/windows/win32/api/winnls/nf-winnls-getnumberformata)
> 
> We could use ifdefs to keep the old logic on Linux and use new logic on Windows (for all compilers).
> 
> Let me know if this is something that would need to be done, or if the current output
> without thousands grouping is good enough.
> --
The thousands grouping is incredibly helpful when working with large
numbers, but given the lack of support for this on Windows, we'll just have
to go without, I think.

/Bruce