On 1/3/22 6:15 PM, Martin Maechler wrote:
Hugh Parsonage
on Wed, 29 Dec 2021 00:36:51 +1100 writes:
> In src/main/printvector.c in the definition of printVector and
> printNamedVector (and elsewhere):
> Rprintf(" [ reached getOption(\"max.print\") -- omitted %d entries ]\n",
> n - n_pr);
> Though n - n_pr is of type R_xlen_t so may not be representable as
> int. In practice negative values may be observed for long vectors.
> Rprintf(" [ reached getOption(\"max.print\") -- omitted %lld entries
]\n",
> n - n_pr);
Thank you Hugh, for finding and reporting this,
including a proposed remedy.
At some point in time, I think the %lld format specifier was
not portable enough to all versions of C compiler / libraries
that were considered valid for compiling R.
See e.g.,
https://stackoverflow.com/questions/462345/format-specifier-for-long-long
which says that "it" does not work on Windows.
Maybe this has changed now that we require C99 and also that
since R version 4.0.0 (or 4.0.1) we also use a somewhat more
recent version of gcc also on Windows?
... ah, searching the R sources reveals uses of %lld
*plus*
#ifdef Win32
#include <trioremap.h> /* for %lld */
#endif
so it seems we can and should probably change this ...
UCRT on Windows supports the C99 format, so %lld works, but there is a
bug in GCC which causes a compilation warning to appear for %lld.
There is an open GCC bug report with a patch. It has not been adopted,
yet, but I got reviews from two people and patched the build of GCC in
Rtools42. So, %lld etc now works without a warning for us on Windows and
certainly can be used in package code.
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95130
For base R, as we have been using the trio remap to get rid of the
warning with %lld, it would make sense to keep doing this for
consistency. Eventually we might be able to remove the dependency on
trio, after checking that the other problems due to which we use it have
been resolved in UCRT.
Tomas
[Please, C compiler / library standard experts, chime in !]
Martin Maechler
ETH Zurich and R core team
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