Hi,

this patch fixes testsuite PR80220 - "relative line numbers don't work 
when put between braces".


Consider gcc/testsuite/gcc.dg/990506-0.c, which has absolute line 
numbers between braces:
...
$ cat -n 990506-0.c
      1	/* Verify that a diagnostic is issued without crashing due to
      2	   --enable-checking catching a bug in the C front end.  */
      3	/* { dg-do compile } */
      4	x()
      5	{
      6	  foo (i);
      7	  /* { dg-error "undeclared" "undeclared-variable message" { 
target *-*-* } { 6 } } */
      8	  /* { dg-message "function it appears in" "reminder message" { 
target *-*-* } { 6 } } */
      9	}
...

When we rewrite the test to use relative line numbers:
...
diff --git a/gcc/testsuite/gcc.dg/990506-0.c 
b/gcc/testsuite/gcc.dg/990506-0.c
index 3cd3be3..08ba856 100644
--- a/gcc/testsuite/gcc.dg/990506-0.c
+++ b/gcc/testsuite/gcc.dg/990506-0.c
@@ -4,6 +4,6 @@
  x()
  {
    foo (i);
-  /* { dg-error "undeclared" "undeclared-variable message" { target 
*-*-* } { 6 } } */
-  /* { dg-message "function it appears in" "reminder message" { target 
*-*-* } { 6 } } */
+  /* { dg-error "undeclared" "undeclared-variable message" { target 
*-*-* } { .-1 } } */
+  /* { dg-message "function it appears in" "reminder message" { target 
*-*-* } { .-2 } } */
  }
...

we run into trouble:
...
ERROR: gcc.dg/990506-0.c: expected integer but got " .-1 " for " 
dg-error 7 "undeclared" "undeclared-variable message" { target *-*-* } { 
.-1 } "
...

The problem is that the relative line number is written between braces, 
which results in whitespace before and after the number, and the 
relative line number handling in process-message doesn't handle that 
whitespace well.

This patch fixes that.

Bootstrapped and reg-tested on x86_64.

OK for stage4 or stage1 trunk?

Thanks,
- Tom