diff --git a/ChangeLog b/ChangeLog
index d0e1ad94..bdbff165 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,9 @@
+2000-03-21  Akim Demaille  <akim@epita.fr>
+
+	* autoconf.sh (task trace): Pipe the output of the first m4 into
+	the second one, instead of saving to a tmp file, so that we can
+	trace endless configure.in expansion.
+
 2000-03-21  Akim Demaille  <akim@epita.fr>
 
 	Uniform idioms.
diff --git a/autoconf.in b/autoconf.in
index 4e010b14..ccfaf805 100644
--- a/autoconf.in
+++ b/autoconf.in
@@ -440,21 +440,19 @@ EOF
   fi
 
   # Run m4 on the input file to get traces.
-  $verbose "Running $run_m4_trace $infile" >&2
+  $verbose "Running $run_m4_trace $infile | $M4 $trace_m4" >&2
   $run_m4_trace $infile 2>&1 >/dev/null |
     sed -e 's/^m4trace:\([^:][^:]*\):\([0-9][0-9]*\): -\([0-9][0-9]*\)- \([^(][^(]*\)(\(.*\)$/AT_\4([\1], [\2], [\3], [\4], \5/' \
-        -e 's/^m4trace:\([^:][^:]*\):\([0-9][0-9]*\): -\([0-9][0-9]*\)- \(.*\)$/AT_\4([\1], [\2], [\3], [\4])/' >>$trace_m4
-
+        -e 's/^m4trace:\([^:][^:]*\):\([0-9][0-9]*\): -\([0-9][0-9]*\)- \(.*\)$/AT_\4([\1], [\2], [\3], [\4])/' |
   # Now we are ready to run m4 to process the trace file.
+  $M4 $trace_m4 - |
   # It makes no sense to try to transform __oline__.
-  $verbose "Running $M4 $trace_m4" >&2
-  $M4 $trace_m4 |
-    sed '
-      s/@<:@/[/g
-      s/@:>@/]/g
-      s/@S|@/$/g
-      s/@%:@/#/g
-      ' >&4
+  sed '
+    s/@<:@/[/g
+    s/@:>@/]/g
+    s/@S|@/$/g
+    s/@%:@/#/g
+    ' >&4
   ;;
 
 
diff --git a/autoconf.sh b/autoconf.sh
index 4e010b14..ccfaf805 100644
--- a/autoconf.sh
+++ b/autoconf.sh
@@ -440,21 +440,19 @@ EOF
   fi
 
   # Run m4 on the input file to get traces.
-  $verbose "Running $run_m4_trace $infile" >&2
+  $verbose "Running $run_m4_trace $infile | $M4 $trace_m4" >&2
   $run_m4_trace $infile 2>&1 >/dev/null |
     sed -e 's/^m4trace:\([^:][^:]*\):\([0-9][0-9]*\): -\([0-9][0-9]*\)- \([^(][^(]*\)(\(.*\)$/AT_\4([\1], [\2], [\3], [\4], \5/' \
-        -e 's/^m4trace:\([^:][^:]*\):\([0-9][0-9]*\): -\([0-9][0-9]*\)- \(.*\)$/AT_\4([\1], [\2], [\3], [\4])/' >>$trace_m4
-
+        -e 's/^m4trace:\([^:][^:]*\):\([0-9][0-9]*\): -\([0-9][0-9]*\)- \(.*\)$/AT_\4([\1], [\2], [\3], [\4])/' |
   # Now we are ready to run m4 to process the trace file.
+  $M4 $trace_m4 - |
   # It makes no sense to try to transform __oline__.
-  $verbose "Running $M4 $trace_m4" >&2
-  $M4 $trace_m4 |
-    sed '
-      s/@<:@/[/g
-      s/@:>@/]/g
-      s/@S|@/$/g
-      s/@%:@/#/g
-      ' >&4
+  sed '
+    s/@<:@/[/g
+    s/@:>@/]/g
+    s/@S|@/$/g
+    s/@%:@/#/g
+    ' >&4
   ;;
 
 
diff --git a/bin/autoconf.in b/bin/autoconf.in
index 4e010b14..ccfaf805 100644
--- a/bin/autoconf.in
+++ b/bin/autoconf.in
@@ -440,21 +440,19 @@ EOF
   fi
 
   # Run m4 on the input file to get traces.
-  $verbose "Running $run_m4_trace $infile" >&2
+  $verbose "Running $run_m4_trace $infile | $M4 $trace_m4" >&2
   $run_m4_trace $infile 2>&1 >/dev/null |
     sed -e 's/^m4trace:\([^:][^:]*\):\([0-9][0-9]*\): -\([0-9][0-9]*\)- \([^(][^(]*\)(\(.*\)$/AT_\4([\1], [\2], [\3], [\4], \5/' \
-        -e 's/^m4trace:\([^:][^:]*\):\([0-9][0-9]*\): -\([0-9][0-9]*\)- \(.*\)$/AT_\4([\1], [\2], [\3], [\4])/' >>$trace_m4
-
+        -e 's/^m4trace:\([^:][^:]*\):\([0-9][0-9]*\): -\([0-9][0-9]*\)- \(.*\)$/AT_\4([\1], [\2], [\3], [\4])/' |
   # Now we are ready to run m4 to process the trace file.
+  $M4 $trace_m4 - |
   # It makes no sense to try to transform __oline__.
-  $verbose "Running $M4 $trace_m4" >&2
-  $M4 $trace_m4 |
-    sed '
-      s/@<:@/[/g
-      s/@:>@/]/g
-      s/@S|@/$/g
-      s/@%:@/#/g
-      ' >&4
+  sed '
+    s/@<:@/[/g
+    s/@:>@/]/g
+    s/@S|@/$/g
+    s/@%:@/#/g
+    ' >&4
   ;;