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 "$target" in
  12   *-linux* | *-uclinux*)
  13     case "$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            #include <unistd.h>
  26            int lk;],
  27           [syscall (SYS_gettid); syscall (SYS_futex, &lk, 0, 0, 0);])],
  28           [save_LIBS="$LIBS"
  29            LIBS="-lpthread $LIBS"
  30            AC_LINK_IFELSE(
  31            [AC_LANG_PROGRAM(
  32             [#ifndef _GNU_SOURCE
  33              #define _GNU_SOURCE 1
  34              #endif
  35              #include <pthread.h>
  36              pthread_t th; void *status;],
  37             [pthread_tryjoin_np (th, &status);])],[enable_linux_futex=yes],
  38             [if test x$cross_compiling = xno; then
  39                if getconf GNU_LIBPTHREAD_VERSION 2>/dev/null \
  40                   | LC_ALL=C grep -i NPTL > /dev/null 2>/dev/null; then :; else
  41                  AC_MSG_WARN([The kernel might not support futex or gettid syscalls.
  42 If so, please configure with --disable-linux-futex])
  43                fi
  44              fi
  45              enable_linux_futex=yes])
  46            LIBS="$save_LIBS"])
  47         ;;
  48       yes)
  49         AC_LINK_IFELSE(
  50          [AC_LANG_PROGRAM(
  51           [#include <sys/syscall.h>
  52            #include <unistd.h>
  53            int lk;],
  54           [syscall (SYS_gettid); syscall (SYS_futex, &lk, 0, 0, 0);])],[],
  55           [AC_MSG_ERROR([SYS_gettid and SYS_futex required for --enable-linux-futex])])
  56         ;;
  57     esac
  58     ;;
  59   *)
  60     enable_linux_futex=no
  61     ;;
  62 esac
  63 if test x$enable_linux_futex = xyes; then
  64   $1
  65 fi
  66 ])