On Sat, Mar 16, 2013 at 1:06 AM, Ralf Corsepius <ralf.corsepius@xxxxxxxxx> wrote: > On 03/15/2013 09:13 PM, Zack Weinberg wrote: >> On 2013-03-15 8:57 AM, Ralf Corsepius wrote: >>> >>> aio.h and sys/mman.h are not available everywhere >> >> >> aio.h certainly, but are you aware of a *specific Unix-like system* >> which is in current use and does not provide <sys/mman.h>? > > Unix-like! Not all OSes are Unix-like. The whole point of this project is to pin down the remaining variation among OSes that *are* Unix-like, because IME that is the case where AC_CHECK_HEADERS is most useful. > Most prominent one without mman.h is mingw. Others, I am aware about are > certain newlib based toolchains. This may be skewed by the software I've been working on lately (very network-intensive) but portability to anything Windows-based seems best accomplished by conditioning stuff on #ifdef _WIN32. In particular, I don't see any real value in using AC_CHECK_HEADERS to figure out whether you need sys/socket.h and friends or winsock2.h, because there's going to be variation scattered through the code as well, and _WIN32 makes a reliable master switch for all of it. Similarly, _WIN32 will tell you whether to use sys/mman.h and mmap or windows.h and MapViewOfFile. That's why I wrote the original blog post the way I did: my logic is that you can use _WIN32 to figure out if you've got Windows, and only bother to do autoconf probes for things that are variable among platforms that *aren't* Windows. I'd speculate that the same is true for other decidedly non-POSIX environments; VMS, z/OS, and VxWorks come to mind, altho I have no idea how relevant any of them still are. I don't know which box to put newlib in, though. I know it's used in embedded environments, but I don't know what the underlying OS(es?) are like. >> I'd believe there >> might be embedded mostly-POSIX-compliant environments still that don't >> do virtual memory, but I've never seen one. > > Correct - RTEMS is one of these. We have a rudimentary implementation of > aio.h since 2010 and don't have mmap.h at all. If you send me header lists for RTEMS and any other non-Windows-based embedded systems you think should be considered, I'll be happy to update my tables. As I said elsethread, trailing-edge versions are actually better than brand new ones for this analysis. zw _______________________________________________ Autoconf mailing list Autoconf@xxxxxxx https://lists.gnu.org/mailman/listinfo/autoconf
