From 1d554008b3747c6ccaa8e3a08cc797cfade242f3 Mon Sep 17 00:00:00 2001
From: Ulrich Weigand <ulrich.weigand@de.ibm.com>
Date: Wed, 20 Jun 2018 16:24:16 +0200
Subject: [PATCH] Improve gdb.base/float128.exp failure message

If the "print large128" sub-test fails in a manner that typically
indicates internal overflow due to GDB being built without MPFR
support, explicitly state this in the failure message.

gdb/testsuite/ChangeLog:
2018-06-20  Ulrich Weigand  <uweigand@de.ibm.com>

	* gdb.base/float128.exp: Add comment and improved fail message
	to the failure case of "print large128" test.
---
 gdb/testsuite/ChangeLog             |  5 +++++
 gdb/testsuite/gdb.base/float128.exp | 16 +++++++++++++++-
 2 files changed, 20 insertions(+), 1 deletion(-)

diff --git a/gdb/testsuite/ChangeLog b/gdb/testsuite/ChangeLog
index e981535c30..df218effb4 100644
--- a/gdb/testsuite/ChangeLog
+++ b/gdb/testsuite/ChangeLog
@@ -1,3 +1,8 @@
+2018-06-20  Ulrich Weigand  <uweigand@de.ibm.com>
+
+	* gdb.base/float128.exp: Add comment and improved fail message
+	to the failure case of "print large128" test.
+
 2018-06-19  Simon Marchi  <simon.marchi@ericsson.com>
 
 	* configure.ac: Remove AC_PREREQ.
diff --git a/gdb/testsuite/gdb.base/float128.exp b/gdb/testsuite/gdb.base/float128.exp
index 4c322b8ab3..26cabac776 100644
--- a/gdb/testsuite/gdb.base/float128.exp
+++ b/gdb/testsuite/gdb.base/float128.exp
@@ -75,5 +75,19 @@ gdb_test "print ld" ".* = 10\\.375.*" "the value of ld is changed to 10.375"
 gdb_test "print f128" ".* = 20\\.375.*" "the value of f128 is changed to 20.375"
 
 # Test that we can correctly handle the largest IEEE-128 value
-gdb_test "print large128" ".* = 1\\.18973149535723176508575932662800702e\\+4932" "print large128"
+# Note: If we get "inf" instead of the correct result, we may have run into
+# an internal overflow.  This typically happens on host platforms without
+# native IEEE-128 support where GDB was built without MPFR support.
+set test "print large128"
+gdb_test_multiple "print large128" "$test" {
+    -re ".* = 1\\.18973149535723176508575932662800702e\\+4932.*$gdb_prompt $" {
+	pass "$test"
+    }
+    -re ".* = inf.*$gdb_prompt $" {
+	fail "$test (GDB may be missing MPFR support!)"
+    }
+    -re ".*$gdb_prompt $" {
+	fail "$test"
+    }
+}