--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,12 @@
+2012-01-28  Bruno Haible  <bruno@clisp.org>
+
+	test-framework-sh: Fix test failure with AIX 7.1 diff.
+	* tests/init.sh (compare_): Don't use 'diff -u' if it inserts a space
+	in column 1, like 'diff -c' does.
+	* tests/test-init.sh (test_compare): Don't repeat the test from init.sh
+	whether 'diff -u' is used. Instead, test whether the output contains
+	some '@' character.
+
 2012-01-28  Paul Eggert  <eggert@cs.ucla.edu>
 
 	strtoimax: eliminate need for stdint.h, inttypes.h checks

--- a/tests/init.sh
+++ b/tests/init.sh
@@ -255,7 +255,10 @@
   return 2
 }
 
-if diff_out_=`exec 2>/dev/null; diff -u "$0" "$0" < /dev/null`; then
+if diff_out_=`exec 2>/dev/null; diff -u "$0" "$0" < /dev/null` \
+   && diff -u Makefile "$0" 2>/dev/null | grep '^[+]#!' >/dev/null; then
+  # diff accepts the -u option and does not (like AIX 7 'diff') produce an
+  # extra space on column 1 of every content line.
   if test -z "$diff_out_"; then
     compare_ () { diff -u "$@"; }
   else

--- a/tests/test-init.sh
+++ b/tests/test-init.sh
@@ -50,20 +50,19 @@
   case $- in *x*) ;; *) test -s err && fail_ "err not empty: $(cat err)";; esac
 
   compare empty in >out 2>err && fail=1
-  # Remove the TAB-date suffix on each --- and +++ line,
-  # for both the expected and the actual output files.
-  # Also remove the @@ line, since Solaris 5.10 and GNU diff formats differ:
-  # -@@ -0,0 +1 @@
-  # +@@ -1,0 +1,1 @@
-  cat <<\EOF > exp
+  # Compare against expected output only if compare is using diff -u.
+  if grep @ out >/dev/null; then
+    # Remove the TAB-date suffix on each --- and +++ line,
+    # for both the expected and the actual output files.
+    # Also remove the @@ line, since Solaris 5.10 and GNU diff formats differ:
+    # -@@ -0,0 +1 @@
+    # +@@ -1,0 +1,1 @@
+    sed 's/	.*//;/^@@/d' out > k && mv k out
+    cat <<\EOF > exp
 --- empty
 +++ in
 +xyz
 EOF
-  sed 's/	.*//;/^@@/d' out > k && mv k out
-
-  # Compare against expected output only if compare is using diff -u.
-  if diff -u out out < /dev/null > /dev/null 2>&1; then
     compare exp out || fail=1
   fi
   case $- in *x*) ;; *) test -s err && fail_ "err not empty: $(cat err)";; esac