On 04/12/2013 02:47 PM, NightStrike wrote: >>>> What gave you the impression that link tests are not allowed when cross >>>> compiling? We use link tests all the time. It is run tests that >>>> require a fallback when cross-compiling, not link tests. >>> >>> checking for main in -lpthread... configure: error: link tests are not >>> allowed after AC_NO_EXECUTABLES AC_NO_EXECUTABLES is intentionally not documented in the autoconf manual; here are the comments at its m4 definition: # AC_NO_EXECUTABLES # ----------------- # FIXME: The GCC team has specific needs which the current Autoconf # framework cannot solve elegantly. This macro implements a dirty # hack until Autoconf is able to provide the services its users # need. # # Several of the support libraries that are often built with GCC can't # assume the tool-chain is already capable of linking a program: the # compiler often expects to be able to link with some of such # libraries. # # In several of these libraries, workarounds have been introduced to # avoid the AC_PROG_CC_WORKS test, that would just abort their # configuration. The introduction of AC_EXEEXT, enabled either by # libtool or by CVS autoconf, have just made matters worse. # # Unlike an earlier version of this macro, using AC_NO_EXECUTABLES does # not disable link tests at autoconf time, but at configure time. # This allows AC_NO_EXECUTABLES to be invoked conditionally. >>> >>> That's me trying to use AC_CHECK_LIB when cross compiling. Why are you using AC_NO_EXECUTABLES? Are you working on gcc? If so, this question is better asked on the gcc list. If not, then don't use it. >> >> please post full config.logs. what you've shown is that your compiler has been >> flagged as not being able to produce executables which is very different from >> "is it a cross-compiler". >> -mike > > Attached. Interesting, though, when I don't cross compile, the check > executes. And, I've always seen this when I try to cross compile. > > I must have something fundamentally wrong in my understanding. > Hopefully, the attached log helps you to enlighten me. The reason that gcc rejects link tests is because of historical baggage of how the uber-tree is used to build an entire cross environment (libraries, gcc, gdb, and more, all in one go) - in THAT environment, configure can't perform link tests, because the tests would have to link against the cross-built libraries, but this is the configure script trying to set up those cross-built libraries (they don't exist yet, so the link test will do the wrong thing). Outside of gcc's special needs, you should generally have no problem pre-installing cross-built libraries, at which point, you should have no need for AC_NO_EXECUTABLES in your configure.ac. -- Eric Blake eblake redhat com +1-919-301-3266 Libvirt virtualization library http://libvirt.org
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