[R-pkg-devel] Canonical way to Rprintf R_xlen_t

[Reed A. Cartwright]

If I have read the R's change log correctly, C99 printf format is now
supported on Windows. I think the change was made in the last week.

On Tue, Nov 28, 2023, 13:01 Henrik Bengtsson <henrik.bengtsson using gmail.com>
wrote:

> "%td" is not supported on all platforms/compilers.  This is what I got
> when I added it to 'matrixStats';
>
> * using log directory
> 'D:/a/matrixStats/matrixStats/check/matrixStats.Rcheck'
> * using R Under development (unstable) (2023-11-26 r85638 ucrt)
> * using platform: x86_64-w64-mingw32
> * R was compiled by
> gcc.exe (GCC) 12.3.0
> GNU Fortran (GCC) 12.3.0
> * running under: Windows Server 2022 x64 (build 20348)
> * using session charset: UTF-8
> * using options '--no-manual --as-cran'
> * checking for file 'matrixStats/DESCRIPTION' ... OK
> * this is package 'matrixStats' version '1.1.0-9003'
> * checking package namespace information ... OK
> * checking package dependencies ... OK
> * checking if this is a source package ... OK
> * checking if there is a namespace ... OK
> * checking for executable files ... OK
> * checking for hidden files and directories ... OK
> * checking for portable file names ... OK
> * checking serialization versions ... OK
> * checking whether package 'matrixStats' can be installed ... [22s] WARNING
> Found the following significant warnings:
> binCounts.c:25:81: warning: unknown conversion type character 't' in
> format [-Wformat=]
> binCounts.c:25:11: warning: too many arguments for format
> [-Wformat-extra-args]
> binMeans.c:26:60: warning: unknown conversion type character 't' in
> format [-Wformat=]
> binMeans.c:26:67: warning: unknown conversion type character 't' in
> format [-Wformat=]
> ...
> See 'D:/a/matrixStats/matrixStats/check/matrixStats.Rcheck/00install.out'
> for details.
> * used C compiler: 'gcc.exe (GCC) 12.2.0'
>
> It worked fine on Linux. Because of this, I resorted to the coercion
> strategy, i.e. "%lld" and (long long int)value.  FWIW, on MS Windows,
> I see 'ptrsize_t' being 'long long int', whereas on Linux I see 'long
> int'.
>
> /Henrik
>
> On Tue, Nov 28, 2023 at 11:51 AM Ivan Krylov <krylov.r00t using gmail.com>
> wrote:
> >
> > On Wed, 29 Nov 2023 06:11:23 +1100
> > Hugh Parsonage <hugh.parsonage using gmail.com> wrote:
> >
> > > Rprintf("%lld", (long long) xlength(x));
> >
> > This is fine. long longs are guaranteed to be at least 64 bits in size
> > and are signed, just like lengths in R.
> >
> > > Rprintf("%td, xlength(x));
> >
> > Maybe if you cast it to ptrdiff_t first. Otherwise I would expect this
> > to fail on an (increasingly rare) 32-bit system where R_xlen_t is int
> > (which is an implementation detail).
> >
> > In my opinion, ptrdiff_t is just the right type for array lengths if
> > they have to be signed (which is useful for Fortran interoperability),
> > so Rprintf("%td", (ptrdiff_t)xlength(x)) would be my preferred option
> > for now. By definition of ptrdiff_t, you can be sure [*] that there
> > won't be any vectors on your system longer than PTRDIFF_MAX.
> >
> > > using the string macro found in Mr Kalibera's commit of r85641:
> > > R_PRIdXLEN_T
> >
> > I think this will be the best solution once we can afford
> > having our packages depend on R >= 4.4.
> >
> > --
> > Best regards,
> > Ivan
> >
> > [*]
> https://urldefense.com/v3/__https://en.cppreference.com/w/c/types/ptrdiff_t__;!!IKRxdwAv5BmarQ!Zm84sWjl9Vg2_hQ8e5geMYnVFH8eNO-9KZsIkE7Tjk_V_-tj8W2Ept9o43gl-WGDczLbJTORU0oHTnfSA5iTLmO_uTKw$
> posits that there
> > may exist long vectors that fit in SIZE_MAX (unsigned) elements but not
> > PTRDIFF_MAX (signed) elements. If such vector exists, subtracting two
> > pointers to its insides may result in undefined behaviour. This may be
> > already possible in a 32-bit process on Linux running with a 3G
> > user-space / 1G kernel-space split. The only way around the problem is
> > to use unsigned types for lengths, but that would preclude Fortran
> > compatibility.
> >
> > ______________________________________________
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> >
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