On Wed, 10 Mar 2010, Szak�ts Viktor wrote: Hi,
> > It's interesting to check if there are any speed differences in MSVC C and > > C++ builds. > > Can you check it? > I checked mingw-tdm-2 4.4.1, and C++ turned out to be consistently > faster by 5% than plain C. Calculated by 4-4 speedtst runs, dropping > min/max and averaging rest 2-2 results. > Env: MBP iC2D/2.8 -> OS X 10.6 (64-bit kernel) -> VMWare 3.0.2 -> Win7 x64 It's similar to mine results. GCC4 in C++ mode for sure uses more extensively strict aliasing optimization. At least it was reporting more errors and warnings for Harbour core code which was using casting ignoring aliasing rules. BTW this ones are still reported: ../../../hb_btree.c: In function ‘ioOneBufferAlloc’: ../../../hb_btree.c:275:3: warning: dereferencing type-punned pointer will break strict-aliasing rules This seems to be also real bug which may cause GPF on some platforms but I'm not familiar enough with this code to fix it myself. ../../../sddfb.c: In function ‘fbDisconnect’: ../../../sddfb.c:181:4: warning: dereferencing type-punned pointer will break strict-aliasing rules ../../../sddfb.c: In function ‘fbOpen’: ../../../sddfb.c:209:4: warning: dereferencing type-punned pointer will break strict-aliasing rules ../../../sddfb.c:219:4: warning: dereferencing type-punned pointer will break strict-aliasing rules This is also danger casting though it should work if void * is large enough to hold FB handlers. Anyhow it's potential problem so it should be fixed. BTW it would be good to check what GCC does when it detects such code or even real problems (it can report also: "dereferencing pointer ... does break strict-aliasing rules"). Does it disable optimization or generates potentially wrong code. Can you compare C and C++ mode in MSVC too? best regards, Przemek _______________________________________________ Harbour mailing list (attachment size limit: 40KB) Harbour@harbour-project.org http://lists.harbour-project.org/mailman/listinfo/harbour
