gcc-dg.exp (process-message): Support relative line number notation - .+4 or .-1 etc.

	* lib/gcc-dg.exp (process-message): Support relative line number
	notation - .+4 or .-1 etc.
	* gcc.dg/dg-test-1.c: New test.

From-SVN: r240391

gcc/testsuite/ChangeLog

+2016-09-23  Jakub Jelinek  <jakub@redhat.com>
+
+	* lib/gcc-dg.exp (process-message): Support relative line number
+	notation - .+4 or .-1 etc.
+	* gcc.dg/dg-test-1.c: New test.
+
 2016-09-22  Martin Sebor  <msebor@redhat.com>
 
 	PR target/77676

gcc/testsuite/lib/gcc-dg.exp

@@ -986,6 +986,13 @@ if { [info procs saved-dg-error] == [list] \
 proc process-message { msgproc msgprefix dgargs } {
     upvar dg-messages dg-messages
 
+    # Handle relative line specification, .+1 or .-1 etc.
+    if { [llength $dgargs] == 5
+	 && [regsub "^\.\[+-\](\[0-9\])$" [lindex $dgargs 4] "\\1" num] } {
+	set num [expr [lindex $dgargs 0] [string index [lindex $dgargs 4] 1] $num]
+	set dgargs [lreplace $dgargs 4 4 $num]
+    }
+
     # Process the dg- directive, including adding the regular expression
     # to the new message entry in dg-messages.
     set msgcnt [llength ${dg-messages}]