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AX_HAVE_EPOLL([ACTION-IF-FOUND], [ACTION-IF-NOT-FOUND])
AX_HAVE_EPOLL_PWAIT([ACTION-IF-FOUND], [ACTION-IF-NOT-FOUND])
This macro determines whether the system supports the epoll I/O event interface. A neat usage example would be:
AX_HAVE_EPOLL( [AX_CONFIG_FEATURE_ENABLE(epoll)], [AX_CONFIG_FEATURE_DISABLE(epoll)]) AX_CONFIG_FEATURE( [epoll], [This platform supports epoll(7)], [HAVE_EPOLL], [This platform supports epoll(7).])
The epoll interface was added to the Linux kernel in version 2.5.45, and the macro verifies that a kernel newer than this is installed. This check is somewhat unreliable if <linux/version.h> doesn't match the running kernel, but it is necessary regardless, because glibc comes with stubs for the epoll_create(), epolL_wait(), etc. that allow programs to compile and link even if the kernel is too old; the problem would then be detected only at runtime.
Linux kernel version 2.6.19 adds the epoll_pwait() call in addition to epoll_wait(). The availability of that function can be tested with the second macro. Generally speaking, it is safe to assume that AX_HAVE_EPOLL would succeed if AX_HAVE_EPOLL_PWAIT has, but not the other way round.
Peter Simons <simons@cryp.to>
2008-05-07
AC_DEFUN([AX_HAVE_EPOLL], [dnl ax_have_epoll_cppflags="${CPPFLAGS}" AC_CHECK_HEADER([linux/version.h], [CPPFLAGS="${CPPFLAGS} -DHAVE_LINUX_VERSION_H"]) AC_MSG_CHECKING([for Linux epoll(7) interface]) AC_CACHE_VAL([ax_cv_have_epoll], [dnl AC_LINK_IFELSE([dnl AC_LANG_PROGRAM([dnl #include <sys/epoll.h> #ifdef HAVE_LINUX_VERSION_H # include <linux/version.h> # if LINUX_VERSION_CODE < KERNEL_VERSION(2,5,45) # error linux kernel version is too old to have epoll # endif #endif ], [dnl int fd, rc; struct epoll_event ev; fd = epoll_create(128); rc = epoll_wait(fd, &ev, 1, 0);])], [ax_cv_have_epoll=yes], [ax_cv_have_epoll=no])]) CPPFLAGS="${ax_have_epoll_cppflags}" AS_IF([test "${ax_cv_have_epoll}" = "yes"], [AC_MSG_RESULT([yes]) $1],[AC_MSG_RESULT([no]) $2]) ])dnl AC_DEFUN([AX_HAVE_EPOLL_PWAIT], [dnl ax_have_epoll_cppflags="${CPPFLAGS}" AC_CHECK_HEADER([linux/version.h], [CPPFLAGS="${CPPFLAGS} -DHAVE_LINUX_VERSION_H"]) AC_MSG_CHECKING([for Linux epoll(7) interface with signals extension]) AC_CACHE_VAL([ax_cv_have_epoll_pwait], [dnl AC_LINK_IFELSE([dnl AC_LANG_PROGRAM([dnl #ifdef HAVE_LINUX_VERSION_H # include <linux/version.h> # if LINUX_VERSION_CODE < KERNEL_VERSION(2,6,19) # error linux kernel version is too old to have epoll_pwait # endif #endif #include <sys/epoll.h> #include <signal.h> ], [dnl int fd, rc; struct epoll_event ev; fd = epoll_create(128); rc = epoll_wait(fd, &ev, 1, 0); rc = epoll_pwait(fd, &ev, 1, 0, (sigset_t const *)(0));])], [ax_cv_have_epoll_pwait=yes], [ax_cv_have_epoll_pwait=no])]) CPPFLAGS="${ax_have_epoll_cppflags}" AS_IF([test "${ax_cv_have_epoll_pwait}" = "yes"], [AC_MSG_RESULT([yes]) $1],[AC_MSG_RESULT([no]) $2]) ])dnl
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