[Python-Dev] Adventures with x64, VS7 and VS8 on Windows (original) (raw)
Mark Hammond mhammond at skippinet.com.au
Mon May 21 04:42:37 CEST 2007
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Hi all, I hope the cross-post is appropriate.
I've started playing with getting the pywin32 extensions building under the AMD64 architecture. I started building with Visual Studio 8 (it was what I had handy) and I struck a few issues relating to the compiler version that I thought worth sharing.
In trying to build x64 from a 32bit VS7 (ie, cross-compiling via the PCBuild directory), the python.exe project fails with:
pythoncore fatal error LNK1112: module machine type 'X86' conflicts with
target machine type 'AMD64'
is this a known issue, or am I doing something wrong?
- The PCBuild8 project files appear to work without modification (I only tried native compilation here though, not a cross-compile) - however, unlike the PCBuild directory, they place all binaries in a 'PCBuild8/x64' directory. While this means that its possible to build for multiple architectures from the same source tree, it makes life harder for tools like 'distutils' - eg, distutils already knows about the 'PCBuild' directory, but it knows nothing about either PCBuild8 or PCBuild8/x64.
A number of other build processes also know to look inside a PCBuild directory (eg, Mozilla), so instead of formalizing PCBuild8, I think we should merge PCBuild8 into PCBuild. This could mean PCBuild/vs7 and PCBuild/vs8 directories with the "project" files, but binaries would still be generated in the 'PCBuild' (or PCBuild/x64) directory. This would mean the same tree isn't capable of hosting 2 builds from different VS compilers, but I think that is reasonable (if it's a problem, just have multiple source directories). I understand that PCBuild8 is not "official", but in the assumption that future versions of Python will use a compiler later than VS7, it makes sense to me to clean this up now - what are others opinions on this?
Re the x64 directory used by the PCBuild8 process. IMO, it makes sense to generate x64 binaries to their own directory - my expectation is that cross-compiling between platforms is a reasonable use-case, and we should support multiple achitectures for the same compiler version. This would mean formalizing the x64 directory in both 'PCBuild' and distutils, and leaving other external build processes to update as they support x64 builds. Does this make sense? Would this fatally break other scripts used for packaging (eg, the MSI framework)?
Wide characters in VS8: PC/pyconfig.h defines PY_UNICODE_TYPE as 'unsigned short', which corresponds with both 'WCHAR' and 'wchar' in previous compiler versions. VS8 defines this as wchar_t, which I'm struggling to find a formal definition for beyond being 2 bytes. My problem is that code which assumes a 'Py_UNICODE *' could be used in place of a 'WCHAR *' now fails. I believe the intent on Windows has always been "PyUNICODE == 'native unicode'" - should PC/pyconfig.h reflect this (ie, should pyconfig.h grow a version specific definition of PyUNICODE as wchar_t)?
Finally, as something from left-field which may well take 12 months or more to pull off - but would there be any interest to moving the Windows build process to a cygwin environment based on the existing autoconf scripts? I know a couple of projects are doing this successfully, including Mozilla, so it has precendent. It does impose a greater burden on people trying to build on Windows, but I'd suggest that in recent times, many people who are likely to want to build Python on Windows are already likely to have a cygwin environment. Simpler mingw builds and nuking MSVC specific build stuff are among the advantages this would bring. It is not worth adding this as "yet another windows build option" - so IMO it is only worth progressing with if it became the "blessed" build process for windows - if there is support for this, I'll work on it as the opportunity presents itself...
I'm (obviously) only suggesting we do this on the trunk and am happy to make all agreed changes - but I welcome all suggestions or critisisms of this endeavour...
Cheers,
Mark
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