diff --git a/aclocal.m4 b/aclocal.m4
index 2b434a047b5..7ecaee59f34 100644
--- a/aclocal.m4
+++ b/aclocal.m4
@@ -50,22 +50,6 @@ then AC_DEFINE_UNQUOTED(AS_TR_CPP(SONAME_LIB$1),"$ac_cv_lib_soname_$1",
                         [Define to the soname of the lib$1 library.])dnl
 fi])
 
-dnl **** Check for reentrant libc ****
-dnl
-dnl Usage: WINE_CHECK_ERRNO(errno-name,[action-if-yes,[action-if-no]])
-dnl
-dnl For cross-compiling we blindly assume that libc is reentrant. This is
-dnl ok since non-reentrant libc is quite rare (mostly old libc5 versions).
-dnl
-AC_DEFUN([WINE_CHECK_ERRNO],
-[AC_CACHE_CHECK([for reentrant libc: $1],[wine_cv_libc_r_$1],
-  [AC_TRY_RUN([int myerrno = 0;
-int *$1(){return &myerrno;}
-main(){close(333); close(333); exit(!myerrno);}],
-  wine_cv_libc_r_$1=yes, wine_cv_libc_r_$1=no,
-  wine_cv_libc_r_$1=yes)])
-AS_IF([test "$wine_cv_libc_r_$1" = "yes"],[$2],[$3])])
-
 dnl **** Link C code with an assembly file ****
 dnl
 dnl Usage: WINE_TRY_ASM_LINK(asm-code,includes,function,[action-if-found,[action-if-not-found]])
diff --git a/configure b/configure
index 0149a3c6d8e..8cf54d94de2 100755
--- a/configure
+++ b/configure
@@ -12581,297 +12581,6 @@ fi
 
 
 
-wine_cv_libc_reentrant=no
-echo "$as_me:$LINENO: checking for reentrant libc: __errno_location" >&5
-echo $ECHO_N "checking for reentrant libc: __errno_location... $ECHO_C" >&6
-if test "${wine_cv_libc_r___errno_location+set}" = set; then
-  echo $ECHO_N "(cached) $ECHO_C" >&6
-else
-  if test "$cross_compiling" = yes; then
-  wine_cv_libc_r___errno_location=yes
-else
-  cat >conftest.$ac_ext <<_ACEOF
-#line $LINENO "configure"
-/* confdefs.h.  */
-_ACEOF
-cat confdefs.h >>conftest.$ac_ext
-cat >>conftest.$ac_ext <<_ACEOF
-/* end confdefs.h.  */
-int myerrno = 0;
-int *__errno_location(){return &myerrno;}
-main(){close(333); close(333); exit(!myerrno);}
-_ACEOF
-rm -f conftest$ac_exeext
-if { (eval echo "$as_me:$LINENO: \"$ac_link\"") >&5
-  (eval $ac_link) 2>&5
-  ac_status=$?
-  echo "$as_me:$LINENO: \$? = $ac_status" >&5
-  (exit $ac_status); } && { ac_try='./conftest$ac_exeext'
-  { (eval echo "$as_me:$LINENO: \"$ac_try\"") >&5
-  (eval $ac_try) 2>&5
-  ac_status=$?
-  echo "$as_me:$LINENO: \$? = $ac_status" >&5
-  (exit $ac_status); }; }; then
-  wine_cv_libc_r___errno_location=yes
-else
-  echo "$as_me: program exited with status $ac_status" >&5
-echo "$as_me: failed program was:" >&5
-sed 's/^/| /' conftest.$ac_ext >&5
-
-( exit $ac_status )
-wine_cv_libc_r___errno_location=no
-fi
-rm -f core core.* *.core gmon.out bb.out conftest$ac_exeext conftest.$ac_objext conftest.$ac_ext
-fi
-fi
-echo "$as_me:$LINENO: result: $wine_cv_libc_r___errno_location" >&5
-echo "${ECHO_T}$wine_cv_libc_r___errno_location" >&6
-if test "$wine_cv_libc_r___errno_location" = "yes"; then
-  wine_cv_libc_reentrant=__errno_location
-else
-    echo "$as_me:$LINENO: checking for reentrant libc: __error" >&5
-echo $ECHO_N "checking for reentrant libc: __error... $ECHO_C" >&6
-if test "${wine_cv_libc_r___error+set}" = set; then
-  echo $ECHO_N "(cached) $ECHO_C" >&6
-else
-  if test "$cross_compiling" = yes; then
-  wine_cv_libc_r___error=yes
-else
-  cat >conftest.$ac_ext <<_ACEOF
-#line $LINENO "configure"
-/* confdefs.h.  */
-_ACEOF
-cat confdefs.h >>conftest.$ac_ext
-cat >>conftest.$ac_ext <<_ACEOF
-/* end confdefs.h.  */
-int myerrno = 0;
-int *__error(){return &myerrno;}
-main(){close(333); close(333); exit(!myerrno);}
-_ACEOF
-rm -f conftest$ac_exeext
-if { (eval echo "$as_me:$LINENO: \"$ac_link\"") >&5
-  (eval $ac_link) 2>&5
-  ac_status=$?
-  echo "$as_me:$LINENO: \$? = $ac_status" >&5
-  (exit $ac_status); } && { ac_try='./conftest$ac_exeext'
-  { (eval echo "$as_me:$LINENO: \"$ac_try\"") >&5
-  (eval $ac_try) 2>&5
-  ac_status=$?
-  echo "$as_me:$LINENO: \$? = $ac_status" >&5
-  (exit $ac_status); }; }; then
-  wine_cv_libc_r___error=yes
-else
-  echo "$as_me: program exited with status $ac_status" >&5
-echo "$as_me: failed program was:" >&5
-sed 's/^/| /' conftest.$ac_ext >&5
-
-( exit $ac_status )
-wine_cv_libc_r___error=no
-fi
-rm -f core core.* *.core gmon.out bb.out conftest$ac_exeext conftest.$ac_objext conftest.$ac_ext
-fi
-fi
-echo "$as_me:$LINENO: result: $wine_cv_libc_r___error" >&5
-echo "${ECHO_T}$wine_cv_libc_r___error" >&6
-if test "$wine_cv_libc_r___error" = "yes"; then
-  wine_cv_libc_reentrant=__error
-else
-      echo "$as_me:$LINENO: checking for reentrant libc: ___errno" >&5
-echo $ECHO_N "checking for reentrant libc: ___errno... $ECHO_C" >&6
-if test "${wine_cv_libc_r____errno+set}" = set; then
-  echo $ECHO_N "(cached) $ECHO_C" >&6
-else
-  if test "$cross_compiling" = yes; then
-  wine_cv_libc_r____errno=yes
-else
-  cat >conftest.$ac_ext <<_ACEOF
-#line $LINENO "configure"
-/* confdefs.h.  */
-_ACEOF
-cat confdefs.h >>conftest.$ac_ext
-cat >>conftest.$ac_ext <<_ACEOF
-/* end confdefs.h.  */
-int myerrno = 0;
-int *___errno(){return &myerrno;}
-main(){close(333); close(333); exit(!myerrno);}
-_ACEOF
-rm -f conftest$ac_exeext
-if { (eval echo "$as_me:$LINENO: \"$ac_link\"") >&5
-  (eval $ac_link) 2>&5
-  ac_status=$?
-  echo "$as_me:$LINENO: \$? = $ac_status" >&5
-  (exit $ac_status); } && { ac_try='./conftest$ac_exeext'
-  { (eval echo "$as_me:$LINENO: \"$ac_try\"") >&5
-  (eval $ac_try) 2>&5
-  ac_status=$?
-  echo "$as_me:$LINENO: \$? = $ac_status" >&5
-  (exit $ac_status); }; }; then
-  wine_cv_libc_r____errno=yes
-else
-  echo "$as_me: program exited with status $ac_status" >&5
-echo "$as_me: failed program was:" >&5
-sed 's/^/| /' conftest.$ac_ext >&5
-
-( exit $ac_status )
-wine_cv_libc_r____errno=no
-fi
-rm -f core core.* *.core gmon.out bb.out conftest$ac_exeext conftest.$ac_objext conftest.$ac_ext
-fi
-fi
-echo "$as_me:$LINENO: result: $wine_cv_libc_r____errno" >&5
-echo "${ECHO_T}$wine_cv_libc_r____errno" >&6
-if test "$wine_cv_libc_r____errno" = "yes"; then
-  wine_cv_libc_reentrant=___errno
-else
-        echo "$as_me:$LINENO: checking for reentrant libc: __thr_errno" >&5
-echo $ECHO_N "checking for reentrant libc: __thr_errno... $ECHO_C" >&6
-if test "${wine_cv_libc_r___thr_errno+set}" = set; then
-  echo $ECHO_N "(cached) $ECHO_C" >&6
-else
-  if test "$cross_compiling" = yes; then
-  wine_cv_libc_r___thr_errno=yes
-else
-  cat >conftest.$ac_ext <<_ACEOF
-#line $LINENO "configure"
-/* confdefs.h.  */
-_ACEOF
-cat confdefs.h >>conftest.$ac_ext
-cat >>conftest.$ac_ext <<_ACEOF
-/* end confdefs.h.  */
-int myerrno = 0;
-int *__thr_errno(){return &myerrno;}
-main(){close(333); close(333); exit(!myerrno);}
-_ACEOF
-rm -f conftest$ac_exeext
-if { (eval echo "$as_me:$LINENO: \"$ac_link\"") >&5
-  (eval $ac_link) 2>&5
-  ac_status=$?
-  echo "$as_me:$LINENO: \$? = $ac_status" >&5
-  (exit $ac_status); } && { ac_try='./conftest$ac_exeext'
-  { (eval echo "$as_me:$LINENO: \"$ac_try\"") >&5
-  (eval $ac_try) 2>&5
-  ac_status=$?
-  echo "$as_me:$LINENO: \$? = $ac_status" >&5
-  (exit $ac_status); }; }; then
-  wine_cv_libc_r___thr_errno=yes
-else
-  echo "$as_me: program exited with status $ac_status" >&5
-echo "$as_me: failed program was:" >&5
-sed 's/^/| /' conftest.$ac_ext >&5
-
-( exit $ac_status )
-wine_cv_libc_r___thr_errno=no
-fi
-rm -f core core.* *.core gmon.out bb.out conftest$ac_exeext conftest.$ac_objext conftest.$ac_ext
-fi
-fi
-echo "$as_me:$LINENO: result: $wine_cv_libc_r___thr_errno" >&5
-echo "${ECHO_T}$wine_cv_libc_r___thr_errno" >&6
-if test "$wine_cv_libc_r___thr_errno" = "yes"; then
-  wine_cv_libc_reentrant=__thr_errno
-else
-          echo "$as_me:$LINENO: checking for reentrant libc: __errno" >&5
-echo $ECHO_N "checking for reentrant libc: __errno... $ECHO_C" >&6
-if test "${wine_cv_libc_r___errno+set}" = set; then
-  echo $ECHO_N "(cached) $ECHO_C" >&6
-else
-  if test "$cross_compiling" = yes; then
-  wine_cv_libc_r___errno=yes
-else
-  cat >conftest.$ac_ext <<_ACEOF
-#line $LINENO "configure"
-/* confdefs.h.  */
-_ACEOF
-cat confdefs.h >>conftest.$ac_ext
-cat >>conftest.$ac_ext <<_ACEOF
-/* end confdefs.h.  */
-int myerrno = 0;
-int *__errno(){return &myerrno;}
-main(){close(333); close(333); exit(!myerrno);}
-_ACEOF
-rm -f conftest$ac_exeext
-if { (eval echo "$as_me:$LINENO: \"$ac_link\"") >&5
-  (eval $ac_link) 2>&5
-  ac_status=$?
-  echo "$as_me:$LINENO: \$? = $ac_status" >&5
-  (exit $ac_status); } && { ac_try='./conftest$ac_exeext'
-  { (eval echo "$as_me:$LINENO: \"$ac_try\"") >&5
-  (eval $ac_try) 2>&5
-  ac_status=$?
-  echo "$as_me:$LINENO: \$? = $ac_status" >&5
-  (exit $ac_status); }; }; then
-  wine_cv_libc_r___errno=yes
-else
-  echo "$as_me: program exited with status $ac_status" >&5
-echo "$as_me: failed program was:" >&5
-sed 's/^/| /' conftest.$ac_ext >&5
-
-( exit $ac_status )
-wine_cv_libc_r___errno=no
-fi
-rm -f core core.* *.core gmon.out bb.out conftest$ac_exeext conftest.$ac_objext conftest.$ac_ext
-fi
-fi
-echo "$as_me:$LINENO: result: $wine_cv_libc_r___errno" >&5
-echo "${ECHO_T}$wine_cv_libc_r___errno" >&6
-if test "$wine_cv_libc_r___errno" = "yes"; then
-  wine_cv_libc_reentrant=__errno
-fi
-
-
-fi
-
-fi
-
-fi
-
-fi
-
-
-if test "$wine_cv_libc_reentrant" != "no"
-then
-
-cat >>confdefs.h <<_ACEOF
-#define ERRNO_LOCATION $wine_cv_libc_reentrant
-_ACEOF
-
-fi
-
-
-if test "$have_x" = "yes"
-then
-echo "$as_me:$LINENO: checking for reentrant X libraries" >&5
-echo $ECHO_N "checking for reentrant X libraries... $ECHO_C" >&6
-if test "${wine_cv_x_reentrant+set}" = set; then
-  echo $ECHO_N "(cached) $ECHO_C" >&6
-else
-  libX11_check=none
-    for dir in "$x_libraries" /usr/lib /usr/local/lib /lib; do
-        if test -r $dir/libX11.so; then
-            libX11_check="-D $dir/libX11.so"
-            break
-        fi
-        if test -r $dir/libX11.a; then
-            libX11_check="$dir/libX11.a"
-            break
-        fi
-    done
-    if test "$libX11_check" != "none"; then
-        if nm $libX11_check | grep $wine_cv_libc_reentrant >/dev/null 2>&1
-        then
-            wine_cv_x_reentrant=yes
-        else
-            wine_cv_x_reentrant=no
-        fi
-    else
-        wine_cv_x_reentrant=unknown
-    fi
-fi
-echo "$as_me:$LINENO: result: $wine_cv_x_reentrant" >&5
-echo "${ECHO_T}$wine_cv_x_reentrant" >&6
-fi
-
-
 # The Ultrix 4.2 mips builtin alloca declared by alloca.h only works
 # for constant arguments.  Useless!
 echo "$as_me:$LINENO: checking for working alloca.h" >&5
@@ -17740,13 +17449,6 @@ then
   echo "*** reentrant version of libc."
 fi
 
-if test "$have_x" = "yes" -a "$wine_cv_x_reentrant" != "yes"
-then
-  echo
-  echo "*** Warning: non-reentrant X11 library detected. Multi-threaded"
-  echo "*** applications won't work properly. You should upgrade your X11 library."
-fi
-
 if test "$wine_cv_opengl_version_OK" = "no"
 then
   echo
diff --git a/configure.ac b/configure.ac
index f6c2ab87b68..eeadc297847 100644
--- a/configure.ac
+++ b/configure.ac
@@ -886,58 +886,6 @@ then
 fi
 
 
-dnl **** Check for reentrant libc ****
-
-wine_cv_libc_reentrant=no
-dnl Linux style errno location
-WINE_CHECK_ERRNO([__errno_location], [wine_cv_libc_reentrant=__errno_location],
-  dnl FreeBSD style errno location
-  WINE_CHECK_ERRNO([__error], [wine_cv_libc_reentrant=__error],
-    dnl Solaris style errno location
-    WINE_CHECK_ERRNO([___errno], [wine_cv_libc_reentrant=___errno],
-      dnl UnixWare style errno location
-      WINE_CHECK_ERRNO([__thr_errno], [wine_cv_libc_reentrant=__thr_errno],
-        dnl NetBSD style errno location
-        WINE_CHECK_ERRNO([__errno], [wine_cv_libc_reentrant=__errno])
-))))
-
-if test "$wine_cv_libc_reentrant" != "no"
-then
-  AC_DEFINE_UNQUOTED(ERRNO_LOCATION,$wine_cv_libc_reentrant,
-	             [Define to the name of the function returning errno for reentrant libc])
-fi
-
-dnl **** Check for reentrant X libraries ****
-dnl
-dnl This may fail to determine whether X libraries are reentrant if
-dnl AC_PATH_XTRA does not set x_libraries.
-
-if test "$have_x" = "yes"
-then
-AC_CACHE_CHECK( [for reentrant X libraries], wine_cv_x_reentrant,
-    [libX11_check=none
-    for dir in "$x_libraries" /usr/lib /usr/local/lib /lib; do
-        if test -r $dir/libX11.so; then
-            libX11_check="-D $dir/libX11.so"
-            break
-        fi
-        if test -r $dir/libX11.a; then
-            libX11_check="$dir/libX11.a"
-            break
-        fi
-    done
-    if test "$libX11_check" != "none"; then
-        if nm $libX11_check | grep $wine_cv_libc_reentrant >/dev/null 2>&1
-        then
-            wine_cv_x_reentrant=yes
-        else
-            wine_cv_x_reentrant=no
-        fi
-    else
-        wine_cv_x_reentrant=unknown
-    fi])
-fi
-
 dnl **** Check for functions ****
 
 AC_FUNC_ALLOCA()
@@ -1590,13 +1538,6 @@ then
   echo "*** reentrant version of libc."
 fi
 
-if test "$have_x" = "yes" -a "$wine_cv_x_reentrant" != "yes"
-then
-  echo
-  echo "*** Warning: non-reentrant X11 library detected. Multi-threaded"
-  echo "*** applications won't work properly. You should upgrade your X11 library."
-fi
-
 if test "$wine_cv_opengl_version_OK" = "no"
 then
   echo
diff --git a/include/config.h.in b/include/config.h.in
index 4b5a30a02e4..9c2327292e6 100644
--- a/include/config.h.in
+++ b/include/config.h.in
@@ -10,9 +10,6 @@
 /* Define to 1 if using `alloca.c'. */
 #undef C_ALLOCA
 
-/* Define to the name of the function returning errno for reentrant libc */
-#undef ERRNO_LOCATION
-
 /* Define to 1 if you have `alloca', as a function or macro. */
 #undef HAVE_ALLOCA
 
diff --git a/scheduler/sysdeps.c b/scheduler/sysdeps.c
index ac62ecca101..a996e64ae8b 100644
--- a/scheduler/sysdeps.c
+++ b/scheduler/sysdeps.c
@@ -367,16 +367,15 @@ static int* (*errno_location_ptr)(void) = default_errno_location;
 static int* (*h_errno_location_ptr)(void) = default_h_errno_location;
 
 /***********************************************************************
- *           __errno_location/__error/___errno
+ *           __errno_location/__error/__errno/___errno/__thr_errno
  *
  * Get the per-thread errno location.
  */
-#ifdef ERRNO_LOCATION
-int *ERRNO_LOCATION(void)
-{
-    return errno_location_ptr();
-}
-#endif /* ERRNO_LOCATION */
+int *__errno_location(void) { return errno_location_ptr(); }  /* Linux */
+int *__error(void)          { return errno_location_ptr(); }  /* FreeBSD */
+int *__errno(void)          { return errno_location_ptr(); }  /* NetBSD */
+int *___errno(void)         { return errno_location_ptr(); }  /* Solaris */
+int *__thr_errno(void)      { return errno_location_ptr(); }  /* UnixWare */
 
 /***********************************************************************
  *           __h_errno_location