[committed] Avoid overly-greedy match in dejagnu regexp.

[Jeff Law]

Occasionally I've been seeing failures with the multi-line diagnostics.  
It's never been clear what's causing the spurious failures, though I 
have long suspected a greedy regexp match.

It happened again yesterday with a local change that in no way should 
affect diagnostics, so I finally went searching and found that sure 
enough the multi-line diagnostics had a ".*" in their regexp.  According 
to the comments, the .* is primarily to catch any dg directives that may 
appear -- ie it should eat to EOL, but not multiple lines.  But a .* can 
indeed match a newline and cause it to eat multiple lines.

The fix is simple.  [^\r\n]* will eat to EOL, but not further.

Regression tested on x86_64 and on our internal target.

Committed to the trunk.

Jeff
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commit 14c7757e9b751781360737f53b71f851fc356d3d
Author: Jeff Law <jeffreyalaw@gmail.com>
Date:   Fri Oct 29 11:30:15 2021 -0400

    Avoid overly-greedy match in dejagnu regexp.
    
    Occasionally I've been seeing failures with the multi-line diagnostics.  It's never been clear what's causing the spurious failures, though I have long suspected a greedy regexp match.
    
    It happened again yesterday with a local change that in no way should affect diagnostics, so I finally went searching and found that sure enough the multi-line diagnostics had a ".*" in their regexp.  According to the comments, the .* is primarily to catch any dg directives that may appear -- ie it should eat to EOL, but not multiple lines.  But a .* can indeed match a newline and cause it to eat multiple lines.
    
    The fix is simple.  [^\r\n]* will eat to EOL, but not further.
    
    Regression tested on x86_64 and on our internal target.
    
    gcc/testsuite
    
            * lib/multiline.exp (_build_multiline_regex): Use a better
            regexp than .* to match up to EOL.

diff --git a/gcc/testsuite/lib/multiline.exp b/gcc/testsuite/lib/multiline.exp
index 0e151b6d222..86387f8209b 100644
--- a/gcc/testsuite/lib/multiline.exp
+++ b/gcc/testsuite/lib/multiline.exp
@@ -331,7 +331,7 @@ proc _build_multiline_regex { multiline index } {
 		# Support arbitrary followup text on each non-empty line,
 		# to deal with comments containing containing DejaGnu
 		# directives.
-		append rexp ".*"
+		append rexp "\[^\\n\\r\]*"
 	    }
 	}
 	append rexp "\n"