[R-pkg-devel] [Re] warning: type of ‘zhpevx_’ does not match original declaration [-Wlto-type-mismatch]
On 12/18/20 8:25 AM, Pierre Lafaye de Micheaux wrote:
Dear Ivan, Thank you for your comment. And also for the previous one. I indeed made a mistake with JOBZ, RANGE and UPLO, now changed to: ? ? const char *CJOBZ = jobz[0]; ? ? const char *CRANGE = range[0]; ? ? const char *CUPLO = uplo[0]; ... ? ? delete[] CJOBZ; ? ? delete[] CRANGE; ? ? delete[] CUPLO;
Dear Pierre, this unfortunately still does not look right. You are calling "delete[]" on something you have not allocated with "new". This code will not work (or if so, only by coincidence only sometimes, but crash other times or produce incorrect results) and you should be seeing a number of compiler warnings if not errors. "jobz" is a "char *" (unless something changed from you previous example), so jobz[0] is a "char", so not a pointer at all.
I did a bit of F77 programming almost 20 years ago when I did my Ph.D. thesis, but I never programmed in Fortran 2003. I remember having tried a few months back to use the iso_c_binding approach (before your previous email) with no success. I will give it a try to see if I can make it work.
That would be best, but I would certainly advise against doing runtime tricks (such as copying the memory, etc) to silence benign compiler warnings. The version I was looking at seemed ok to me, and a recent compiler would not emit warnings - perhaps you could just upgrade your OS?? If you just extended the use of the FC_ macros there to make that work also when the hidden character arguments were not used, that would be good enough for now I think. For the iso_c_binding, there is an example in Writing R Extensions (but does not include the complex type). Best, Tomas
Have a nice day. Kind regards, Pierre ------------------------------------------------------------------------ *From:* Ivan Krylov <krylov.r00t at gmail.com> *Sent:* Friday, 18 December 2020 18:16 *To:* Pierre Lafaye de Micheaux <lafaye at unsw.edu.au> *Cc:* Tomas Kalibera <tomas.kalibera at gmail.com>; Prof Brian Ripley <ripley at stats.ox.ac.uk>; R Package Devel <r-package-devel at r-project.org> *Subject:* Re: [R-pkg-devel] [Re] warning: type of ?zhpevx_? does not match original declaration [-Wlto-type-mismatch] Dear Pierre L., I think that the zhpevxC wrapper, as written, may result in undefined behaviour:
??? const char *JOBZ = jobz[0];
??? delete[] JOBZ;
??? delete[] Cap;
This could work okay, depending on how the rest of the package is
written, but in general, it is considered a bad idea for linear algebra
routines to deallocate memory they didn't allocate. ("Pointer
ownership is usually retained by the calling code.")
May I suggest once again the idea of writing a Fortran 2003 wrapper
zhpevxC instead of C++? Subroutines defined using iso_c_binding are
guaranteed to follow the C calling convention, and, this being Fortran,
call zhpevx(...) is guaranteed to match the Fortran calling convention,
bringing you the best of both worlds:
https://stat.ethz.ch/pipermail/r-package-devel/2020q3/005710.html
No need to allocate or deallocate memory or provide different
definitions depending on the availability of FC_LEN_T, just make sure
that both prototypes mean the same thing. By the way,
std::complex<double> is guaranteed to match the memory layout of C type
double _Complex and Fortran type complex(kind = c_double_complex) by
the respective standards.
--
Best regards,
Ivan