diff --git a/nptl/sysdeps/pthread/configure b/nptl/sysdeps/pthread/configure
index 3f7dcd61f3..6b3c79b8f4 100644
--- a/nptl/sysdeps/pthread/configure
+++ b/nptl/sysdeps/pthread/configure
@@ -122,7 +122,7 @@ fi
   # interfere with the next link command; also delete a directory that is
   # left behind by Apple's compiler.  We do this before executing the actions.
   rm -rf conftest.dSYM conftest_ipa8_conftest.oo
-  eval $as_lineno_stack; test "x$as_lineno_stack" = x && { as_lineno=; unset as_lineno;}
+  eval $as_lineno_stack; ${as_lineno_stack:+:} unset as_lineno
   as_fn_set_status $ac_retval
 
 } # ac_fn_c_try_link
@@ -148,7 +148,7 @@ fi
 
 { $as_echo "$as_me:${as_lineno-$LINENO}: checking for forced unwind support" >&5
 $as_echo_n "checking for forced unwind support... " >&6; }
-if test "${libc_cv_forced_unwind+set}" = set; then :
+if ${libc_cv_forced_unwind+:} false; then :
   $as_echo_n "(cached) " >&6
 else
   cat confdefs.h - <<_ACEOF >conftest.$ac_ext
@@ -182,7 +182,7 @@ if test $libc_cv_forced_unwind = yes; then
   CFLAGS="$CFLAGS -Werror -fexceptions"
   { $as_echo "$as_me:${as_lineno-$LINENO}: checking for C cleanup handling" >&5
 $as_echo_n "checking for C cleanup handling... " >&6; }
-if test "${libc_cv_c_cleanup+set}" = set; then :
+if ${libc_cv_c_cleanup+:} false; then :
   $as_echo_n "(cached) " >&6
 else
     cat confdefs.h - <<_ACEOF >conftest.$ac_ext
diff --git a/nptl/sysdeps/x86_64/configure b/nptl/sysdeps/x86_64/configure
index 4639c222fa..ee047153c9 100644
--- a/nptl/sysdeps/x86_64/configure
+++ b/nptl/sysdeps/x86_64/configure
@@ -85,7 +85,7 @@ $as_echo X/"$0" |
 
 { $as_echo "$as_me:${as_lineno-$LINENO}: checking for .cfi_personality and .cfi_lsda pseudo-ops" >&5
 $as_echo_n "checking for .cfi_personality and .cfi_lsda pseudo-ops... " >&6; }
-if test "${libc_cv_asm_cfi_personality+set}" = set; then :
+if ${libc_cv_asm_cfi_personality+:} false; then :
   $as_echo_n "(cached) " >&6
 else
     cat > conftest.s <<EOF
diff --git a/sysdeps/unix/sysv/linux/configure b/sysdeps/unix/sysv/linux/configure
index d05bd13982..816289a797 100644
--- a/sysdeps/unix/sysv/linux/configure
+++ b/sysdeps/unix/sysv/linux/configure
@@ -112,7 +112,7 @@ fi
 
 { $as_echo "$as_me:${as_lineno-$LINENO}: checking for grep that handles long lines and -e" >&5
 $as_echo_n "checking for grep that handles long lines and -e... " >&6; }
-if test "${ac_cv_path_GREP+set}" = set; then :
+if ${ac_cv_path_GREP+:} false; then :
   $as_echo_n "(cached) " >&6
 else
   if test -z "$GREP"; then
@@ -175,7 +175,7 @@ $as_echo "$ac_cv_path_GREP" >&6; }
 
 { $as_echo "$as_me:${as_lineno-$LINENO}: checking for egrep" >&5
 $as_echo_n "checking for egrep... " >&6; }
-if test "${ac_cv_path_EGREP+set}" = set; then :
+if ${ac_cv_path_EGREP+:} false; then :
   $as_echo_n "(cached) " >&6
 else
   if echo a | $GREP -E '(a|b)' >/dev/null 2>&1
@@ -242,7 +242,7 @@ $as_echo "$ac_cv_path_EGREP" >&6; }
 
 { $as_echo "$as_me:${as_lineno-$LINENO}: checking installed Linux kernel header files" >&5
 $as_echo_n "checking installed Linux kernel header files... " >&6; }
-if test "${libc_cv_linux2010+set}" = set; then :
+if ${libc_cv_linux2010+:} false; then :
   $as_echo_n "(cached) " >&6
 else
   cat confdefs.h - <<_ACEOF >conftest.$ac_ext
diff --git a/sysdeps/x86_64/elf/configure b/sysdeps/x86_64/elf/configure
index cb8db2d54d..c3c8f561fe 100644
--- a/sysdeps/x86_64/elf/configure
+++ b/sysdeps/x86_64/elf/configure
@@ -87,7 +87,7 @@ if test "$usetls" != no; then
 # Check for support of thread-local storage handling in assembler and linker.
 { $as_echo "$as_me:${as_lineno-$LINENO}: checking for x86-64 TLS support" >&5
 $as_echo_n "checking for x86-64 TLS support... " >&6; }
-if test "${libc_cv_x86_64_tls+set}" = set; then :
+if ${libc_cv_x86_64_tls+:} false; then :
   $as_echo_n "(cached) " >&6
 else
   cat > conftest.s <<\EOF