Hi G M, The DWORDs should not have been there at all as _BitScanReverse64 and _BitScanForward formally take unsigned long* and not DWORD* (although they are the same thing).
http://msdn.microsoft.com/en-us/library/wfd9z0bb(v=vs.90).aspx Use unsigned long instead of DWORD and wtypes.h will not be needed. Yaron 2013/12/23 G M <[email protected]> > Hello Win32 libcxx watchers. > support.h implements the functions clz, clzl, clzll, ctz, ctzl, and ctzll > functions (I hate those names) for Win32 when the compiler does not support > them. So ms's cl.exe uses the implementations in support.h but clang and > gcc compilers provide these implementations themselves, not support.h. > > Currently these support.h implementations have a few problems. > > With the removal of windows.h from support.h they no longer compile. Even > when they did compile, they were incorrect at runtime. In more detail: > > 1. support.h now fails to compile for msvc (cl.exe) because it depended on > things like DWORD from windows.h which was removed in a prior commit and no > lighter weight replacement for windows.h was provided. This patch supplies > that with wtypes.h > > 2. These functions aren't implemented for 32 bit targets of cl.exe but > they should be as they are available in the 32 bit and 64 bit gcc and clang > targets. This is because the current implementations use BitScanForward64 > etc. which aren't available to 32 bit targets. This patch provides 32 bit > implementations of the clt/l/ll and clz/l/ll functions to fix that > . > 3. The above named functions current implementation in support.h is > incorrect. The return values of the support.h versions don't match the gcc > or clang return values when given the same inputs. > > The attached support.h.diff patch fixes these problems. > > Anyone wanting to verify the above statements: compile the attached test > case bittests.cpp with MS's 32 bit compiler cl.exe against the SVN version > of libcxx and it's support.h (i.e. before applying the support.h.diff > patch), you will see: > cl bittest.cpp -I/libcxx/include > c:\libcxx\include\support/win32/support.h(85) : error C2065: 'DWORD' : > undeclared identifier > <etc...> This is demonstrates problem 1 above. > > If you edit that svn version of support.h and add wtypes.h and compile > again, you will see the first errors vanish. but then you then you will see > these errors: > c:\libcxx\include\support\win32\support.h(97) : error C3861: > '_BitScanReverse64': identifier not found > c:\libcxx\include\support\win32\support.h(112) : error C3861: > '_BitScanForward64': identifier not found > This demonstrates problem 2 above. > > Switching to the 64 bit cl.exe compiler, if you compile with that, you > should be able to run it but get these runtime errors: > Test ctz failed. line 23, expected value: 32, actual value: 0 > Test ctzl failed. line 33, expected value: 32, actual value: 0 > Test ctzll failed. line 44, expected value: 64, actual value: 0 > Test clz failed. line 57, expected value: 32, actual value: 0 > <snip> > 134 tests failed > This demonstrates problem number 3. > > If you try compiling and runing this file with g++ or clang, you should > see no errors. This shows gcc and clang's implementations of the clt/clz > functions are ok yet support.h's version are not. > If you delete support.h and re get (assuming you modified it to add > wtypes.h) and then apply the support.h.diff patch and then re-compile with > g++, clang++ or cl.exe in 32 bit or 64 bit mode, the test case should then > run with no errors or output for all of those compilers, hopefully > indicating success with no regressions and proving that all the issues > stated were real and that this patch has fixed all the stated problems. > > I am going on holiday the day after tomorrow and won't have access to > email unfortunately so I won't be able to reply to any questions after > tomorrow for about a week, but I thought I'd make this patch available in > the mean time for review and anyone who wants to play with it. I'll try to > reply to any early responses that come in to this patch before I go though. > > Thanks >
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