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c++rdll32bit-64bitr-package

Building R package on win32: Unable to load shared object (.dll)

I'm updating an R package that I last released (with no problems) on R3.6. I've since updated to R 4.0.0 and Rtools 40.

The package builds and runs successfully on 64-bit R. But I see that on win builder, the package's testthat tests fail on win32 (but not win64).

To diagnose the failure, I'm building the package on my 64-bit Windows 10 machine, using a 32-bit version of R and devtools::install(args= "--no-multiarch"). I've edited the PATH environment variable, replacing:

  • C:\Program Files\R\R-4.0.0\bin\x64 with C:\Program Files\R\R-4.0.0\bin\i386
  • C:\rtools40\mingw64\bin with C:\rtools40\mingw32\bin (and I've also tried C:\rtools40\clang32\bin)

The install process is indeed looking to mingw32 for the g++ and gcc executables. Installation is successful, with no warnings or errors.

However, when I attempt to load the package with devtools::load_all(), I see:

Error in inDL(x, as.logical(local), as.logical(now), ...) : 
  unable to load shared object 'C:/path/to/PACKAGENAME/src/PACKAGENAME.dll':
  LoadLibrary failure:  %1 is not a valid Win32 application.

If I instead run library('PACKAGENAME'), then run tests, the R GUI freezes and exits silently -- paralleling the failure on win builder.

I'm struggling to diagnose why a DLL that works perfectly on 64-bit won't work on a 32-bit architecture. The only substantive change I've made to the C++ code is to replace some ints with typedef int16_t xint.

Solution

  • The problem seems to have been the existence of 64-bit dlls in the package's source folder (as insinuated by the error message), created by 'devtools'.

    Once these files were deleted load_all would happily re-create them using the 32-bit compilers.