config/futex.m4

   1 dnl ----------------------------------------------------------------------
   2 dnl This whole bit snagged from libgomp.
   3
   4 dnl
   5 dnl GCC_LINUX_FUTEX
   6 dnl    (SHELL-CODE_HANDLER)
   7 dnl
   8 AC_DEFUN([GCC_LINUX_FUTEX],[dnl
   9 GCC_ENABLE(linux-futex,default, ,[use the Linux futex system call],
  10            permit yes|no|default)
  11 case "$target" in
  12   *-linux*)
  13     case "$enable_linux_futex" in
  14       default)
  15         # If headers don't have gettid/futex syscalls definition, then
  16         # default to no, otherwise there will be compile time failures.
  17         # Otherwise, default to yes.  If we don't detect we are
  18         # compiled/linked against NPTL and not cross-compiling, check
  19         # if programs are run by default against NPTL and if not, issue
  20         # a warning.
  21         enable_linux_futex=no
  22         AC_LINK_IFELSE(
  23          [AC_LANG_PROGRAM(
  24           [#include <sys/syscall.h>
  25            int lk;],
  26           [syscall (SYS_gettid); syscall (SYS_futex, &lk, 0, 0, 0);])],
  27           [save_LIBS="$LIBS"
  28            LIBS="-lpthread $LIBS"
  29            AC_LINK_IFELSE(
  30            [AC_LANG_PROGRAM(
  31             [#ifndef _GNU_SOURCE
  32              #define _GNU_SOURCE 1
  33              #endif
  34              #include <pthread.h>
  35              pthread_t th; void *status;],
  36             [pthread_tryjoin_np (th, &status);])],[enable_linux_futex=yes],
  37             [if test x$cross_compiling = xno; then
  38                if getconf GNU_LIBPTHREAD_VERSION 2>/dev/null \
  39                   | LC_ALL=C grep -i NPTL > /dev/null 2>/dev/null; then :; else
  40                  AC_MSG_WARN([The kernel might not support futex or gettid syscalls.
  41 If so, please configure with --disable-linux-futex])
  42                fi
  43              fi
  44              enable_linux_futex=yes])
  45            LIBS="$save_LIBS"])
  46         ;;
  47       yes)
  48         AC_LINK_IFELSE(
  49          [AC_LANG_PROGRAM(
  50           [#include <sys/syscall.h>
  51            int lk;],
  52           [syscall (SYS_gettid); syscall (SYS_futex, &lk, 0, 0, 0);])],[],
  53           [AC_MSG_ERROR([SYS_gettid and SYS_futex required for --enable-linux-futex])])
  54         ;;
  55     esac
  56     ;;
  57   *)
  58     enable_linux_futex=no
  59     ;;
  60 esac
  61 if test x$enable_linux_futex = xyes; then
  62   $1
  63 fi
  64 ])