diff --git a/lib/gettext.h b/lib/gettext.h
index 65777e6..77db267 100644
--- a/lib/gettext.h
+++ b/lib/gettext.h
@@ -185,7 +185,7 @@ npgettext_aux (const char *domain,
 #include <string.h>
 
 #define _LIBGETTEXT_HAVE_VARIABLE_SIZE_ARRAYS \
-  (((__GNUC__ >= 3 || __GNUG__ >= 2) && !__STRICT_ANSI__) \
+  (((__GNUC__ >= 3 || __GNUG__ >= 2) && !(__STRICT_ANSI__ + 0)) \
    /* || __STDC_VERSION__ >= 199901L */ )
 
 #if !_LIBGETTEXT_HAVE_VARIABLE_SIZE_ARRAYS
diff --git a/lib/math.in.h b/lib/math.in.h
index d3b4839..cc64925 100644
--- a/lib/math.in.h
+++ b/lib/math.in.h
@@ -1188,7 +1188,7 @@ _GL_WARN_REAL_FLOATING_DECL (isnan);
 _GL_EXTERN_C int gl_signbitf (float arg);
 _GL_EXTERN_C int gl_signbitd (double arg);
 _GL_EXTERN_C int gl_signbitl (long double arg);
-#  if __GNUC__ >= 2 && !__STRICT_ANSI__
+#  if __GNUC__ >= 2 && !(__STRICT_ANSI__ + 0)
 #   define _GL_NUM_UINT_WORDS(type) \
       ((sizeof (type) + sizeof (unsigned int) - 1) / sizeof (unsigned int))
 #   if defined FLT_SIGNBIT_WORD && defined FLT_SIGNBIT_BIT && !defined gl_signbitf
diff --git a/lib/regex.h b/lib/regex.h
index 27b2226..89a735d 100644
--- a/lib/regex.h
+++ b/lib/regex.h
@@ -644,7 +644,7 @@ extern int re_exec (const char *);
 #ifndef _Restrict_arr_
 # if ((199901L <= __STDC_VERSION__					\
        || ((3 < __GNUC__ || (3 == __GNUC__ && 1 <= __GNUC_MINOR__))	\
-	   && !__STRICT_ANSI__))					\
+	   && !(__STRICT_ANSI__ + 0)))					\
       && !defined __GNUG__)
 #  define _Restrict_arr_ _Restrict_
 # else
diff --git a/lib/regex_internal.h b/lib/regex_internal.h
index d7413b0..7849e2c 100644
--- a/lib/regex_internal.h
+++ b/lib/regex_internal.h
@@ -334,7 +334,7 @@ typedef struct
     Idx idx;			/* for BACK_REF */
     re_context_type ctx_type;	/* for ANCHOR */
   } opr;
-#if __GNUC__ >= 2 && !__STRICT_ANSI__
+#if __GNUC__ >= 2 && !(__STRICT_ANSI__ + 0)
   re_token_type_t type : 8;
 #else
   re_token_type_t type;
diff --git a/lib/spawn.in.h b/lib/spawn.in.h
index 3c31fd0..8334672 100644
--- a/lib/spawn.in.h
+++ b/lib/spawn.in.h
@@ -63,7 +63,7 @@
 #ifndef _Restrict_arr_
 # if ((199901L <= __STDC_VERSION__                                      \
        || ((3 < __GNUC__ || (3 == __GNUC__ && 1 <= __GNUC_MINOR__))     \
-           && !__STRICT_ANSI__))                                        \
+           && !(__STRICT_ANSI__ + 0)))                                  \
       && !defined __GNUG__)
 #  define _Restrict_arr_ _Restrict_
 # else
diff --git a/m4/absolute-header.m4 b/m4/absolute-header.m4
index b7276a3..0451330 100644
--- a/m4/absolute-header.m4
+++ b/m4/absolute-header.m4
@@ -81,7 +81,10 @@ changequote(,)
       gl_dirsep_regex='/'
       ;;
   esac
-  gl_absolute_header_sed='\|'"${gl_dirsep_regex}"'$1|{
+  dnl Older seds don't support '\#blah#{...}'
+  gl_absolute_header_sed='s,\([/.]\),\\\1,g'
+  gl_absolute_header_match=`printf '%s\n' "${gl_dirsep_regex}"'$1' | sed "$gl_absolute_header_sed"`
+  gl_absolute_header_sed="/${gl_absolute_header_match}/"'{
       s|.*"\(.*'"${gl_dirsep_regex}"'$1\)".*|\1|
       s|^/[^/]|//&|
       p
diff --git a/m4/include_next.m4 b/m4/include_next.m4
index d5230ce..a351b57 100644
--- a/m4/include_next.m4
+++ b/m4/include_next.m4
@@ -223,7 +223,11 @@ changequote(,)
                    ;;
                esac
 changequote([,])
-               gl_absolute_header_sed='\|'"${gl_dirsep_regex}"']m4_defn([gl_HEADER_NAME])[|{
+               dnl Older seds don't support '\#blah#{...}'
+               gl_absolute_header_sed='s,\([/.]\),\\\1,g'
+               gl_absolute_header_match=`printf '%s\n' "${gl_dirsep_regex}"']m4_defn([gl_HEADER_NAME])[' |
+                                         sed "$gl_absolute_header_sed"`
+               gl_absolute_header_sed="/${gl_absolute_header_match}/"'{
                    s|.*"\(.*'"${gl_dirsep_regex}"']m4_defn([gl_HEADER_NAME])[\)".*|\1|
 changequote(,)dnl
                    s|^/[^/]|//&|
diff --git a/m4/perror.m4 b/m4/perror.m4
index 86e2020..5662f44 100644
--- a/m4/perror.m4
+++ b/m4/perror.m4
@@ -27,6 +27,8 @@ AC_DEFUN([gl_FUNC_PERROR],
            [AC_LANG_PROGRAM(
               [[#include <errno.h>
                 #include <stdio.h>
+                #include <stdlib.h>
+                #include <string.h>
               ]],
               [[char *str = strerror (-1);
                 if (!getenv("CONFTEST_OUTPUT")) return 0;
diff --git a/modules/popen b/modules/popen
index 426589a..eb41029 100644
--- a/modules/popen
+++ b/modules/popen
@@ -7,11 +7,11 @@ m4/popen.m4
 
 Depends-on:
 stdio
-open            [test $HAVE_POPEN = 0 || $REPLACE_POPEN = 1]
+open            [test $HAVE_POPEN = 0 || test $REPLACE_POPEN = 1]
 
 configure.ac:
 gl_FUNC_POPEN
-if test $HAVE_POPEN = 0 || $REPLACE_POPEN = 1; then
+if test $HAVE_POPEN = 0 || test $REPLACE_POPEN = 1; then
   AC_LIBOBJ([popen])
   gl_PREREQ_POPEN
 fi
diff --git a/tests/test-printf-posix.c b/tests/test-printf-posix.c
index 9337854..d57f43a 100644
--- a/tests/test-printf-posix.c
+++ b/tests/test-printf-posix.c
@@ -39,7 +39,7 @@ main (int argc, char *argv[])
 }
 
 /* Test whether __attribute__ (__format__ (...)) still works.  */
-#if (__GNUC__ > 2 || (__GNUC__ == 2 && __GNUC_MINOR__ >= 7)) && !__STRICT_ANSI__
+#if (__GNUC__ > 2 || (__GNUC__ == 2 && __GNUC_MINOR__ >= 7)) && !(__STRICT_ANSI__ + 0)
 extern int func1 (char *, size_t, const char *, ...)
      __attribute__ ((__format__ (__printf__, 3, 4)));
 extern int func2 (char *, size_t, const char *, ...)