--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,27 @@
+2009-10-15  Jim Meyering  <meyering@redhat.com>
+
+	don't let environment settings perturb build
+	Setting the envvars, LIB_CLOCK_GETTIME, LIB_EACCESS or LIB_NANOSLEEP
+	could cause a configure-time and/or build-time malfunction.
+	Typically, a configure-time function-in-library test is performed
+	via code like this:
+
+	  LIB_VAR=
+	  AC_SUBST([LIB_VAR])
+	  prefix_saved_LIBS=$LIBS
+	    AC_SEARCH_LIBS([FUNC], [LIB_NAME],
+		       [test "$ac_cv_search_FUNC" = "none required" ||
+			LIB_VAR=$ac_cv_search_FUNC])
+	  LIBS=$prefix_saved_LIBS
+
+	However, in each of the files affected by this change, the LIB_VAR=
+	initialization was omitted.  Thus, when set in the environment, its
+	value would propagate into generated Makefiles when FUNC is not found
+	in LIB_NAME.
+	* m4/clock_time.m4 (gl_CLOCK_TIME): Initialize AC_SUBST'd var.
+	* m4/euidaccess.m4 (gl_PREREQ_EUIDACCESS): Likewise.
+	* m4/nanosleep.m4 (gl_FUNC_NANOSLEEP): Likewise.
+
 2009-10-14  Eric Blake  <ebb9@byu.net>
 
 	fchdir: avoid infinite recursion in mingw

--- a/m4/clock_time.m4
+++ b/m4/clock_time.m4
@@ -20,6 +20,7 @@
   # Save and restore LIBS so e.g., -lrt, isn't added to it.  Otherwise, *all*
   # programs in the package would end up linked with that potentially-shared
   # library, inducing unnecessary run-time overhead.
+  LIB_CLOCK_GETTIME=
   gl_saved_libs=$LIBS
     AC_SEARCH_LIBS([clock_gettime], [rt posix4],
                    [test "$ac_cv_search_clock_gettime" = "none required" ||

--- a/m4/euidaccess.m4
+++ b/m4/euidaccess.m4
@@ -42,6 +42,7 @@
   # Save and restore LIBS so -lgen isn't added to it.  Otherwise, *all*
   # programs in the package would end up linked with that potentially-shared
   # library, inducing unnecessary run-time overhead.
+  LIB_EACCESS=
   gl_saved_libs=$LIBS
     AC_SEARCH_LIBS([eaccess], [gen],
                    [test "$ac_cv_search_eaccess" = "none required" ||

--- a/m4/nanosleep.m4
+++ b/m4/nanosleep.m4
@@ -24,9 +24,10 @@
 
  # Solaris 2.5.1 needs -lposix4 to get the nanosleep function.
  # Solaris 7 prefers the library name -lrt to the obsolescent name -lposix4.
+ LIB_NANOSLEEP=
  AC_SEARCH_LIBS([nanosleep], [rt posix4],
                 [test "$ac_cv_search_nanosleep" = "none required" ||
-	         LIB_NANOSLEEP=$ac_cv_search_nanosleep])
+                 LIB_NANOSLEEP=$ac_cv_search_nanosleep])
 
  AC_REQUIRE([gl_MULTIARCH])
  if test $APPLE_UNIVERSAL_BUILD = 1; then