[Ada catchpoints] Fix "warning: failed to get exception name: No definition of \"e.full_name\" in current context"

Looking at testsuite results, I noticed this warning in an MI test:

 ~"\nCatchpoint "
 ~"2, "
 &"warning: failed to get exception name: No definition of \"e.full_name\" in current context.\n"
 ~"exception at 0x000000000040192d in foo () at /home/pedro/brno/pedro/gdb/mygit/src/gdb/testsuite/gdb.ada/mi_catch_ex/foo.adb:20\n"
 ~"20\t      raise Constraint_Error;  -- SPOT1\n"
 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",exception-name="CONSTRAINT_ERROR",frame={addr="0x000000000040192d",func="foo",args=[],file="/home/pedro/brno/pedro/gdb/mygit/src/gdb/testsuite/gdb.ada/mi_catch_ex/foo.adb",fullname="/home/pedro/brno/pedro/gdb/mygit/src/gdb/testsuite/gdb.ada/mi_catch_ex/foo.adb",line="20"},thread-id="1",stopped-threads="all",core="5"
 (gdb)
 PASS: gdb.ada/mi_catch_ex.exp: continue until CE caught by all-exceptions catchpoint

The problem is that:

  - MI prints the breakpoint hit twice: once on the MI stream;
    another time on the console stream.

  - After printing the Ada catchpoint hit, gdb selects a non-current
    frame, from within the catchpoint's print_it routine.

So the second time the breakpoint is printed, the selected frame is no
longer the current frame, and then evaluating e.full_name in
ada_exception_name_addr fails.

This commit fixes the problem and enhances the gdb.ada/mi_catch_ex.exp
test to make sure the catchpoint hit is printed correctly on the
console stream too.

gdb/ChangeLog:
2016-06-21  Pedro Alves  <palves@redhat.com>

	* ada-lang.c (ada_exception_name_addr_1): Add comment.
	(print_it_exception): Select the current frame.

gdb/testsuite/ChangeLog:
2016-06-21  Pedro Alves  <palves@redhat.com>

	* gdb.ada/mi_catch_ex.exp (continue_to_exception): New procedure.
	(top level): Use it instead of mi_execute_to.

1 files changed, 31 insertions, 10 deletions

diff --git a/gdb/testsuite/gdb.ada/mi_catch_ex.exp b/gdb/testsuite/gdb.ada/mi_catch_ex.exp
index 320f3bfba9..288a0659ba 100644
--- a/gdb/testsuite/gdb.ada/mi_catch_ex.exp
+++ b/gdb/testsuite/gdb.ada/mi_catch_ex.exp
@@ -78,17 +78,38 @@ mi_gdb_test "-catch-exception" \
             "\\^done,bkptno=\"$decimal\",bkpt={.*disp=\"keep\",enabled=\"y\",addr=\"$hex\",what=\"all Ada exceptions\",.*}" \
             "catch all exceptions"
 
-mi_execute_to "exec-continue" \
-              "breakpoint-hit\",disp=\"keep\",bkptno=\"$any_nb\",exception-name=\"CONSTRAINT_ERROR" \
-              "foo" "" ".*" ".*" \
-              ".*" \
-              "continue until CE caught by all-exceptions catchpoint"
+# Continue to caught exception.
 
-mi_execute_to "exec-continue" \
-              "breakpoint-hit\",disp=\"keep\",bkptno=\"$any_nb\",exception-name=\"PROGRAM_ERROR" \
-              "foo" "" ".*" ".*" \
-              ".*" \
-              "continue until PE caught by all-exceptions catchpoint"
+proc continue_to_exception { exception_name test } {
+    global hex any_nb
+
+    mi_send_resuming_command "exec-continue" "$test"
+
+    # Match console stream output.
+    gdb_expect {
+	-re " $exception_name at $hex in foo " {
+	}
+	timeout {
+	    fail "$test (timeout)"
+	    return -1
+	}
+    }
+
+    # Now MI stream output.
+    mi_expect_stop \
+	"breakpoint-hit\",disp=\"keep\",bkptno=\"$any_nb\",exception-name=\"$exception_name" \
+	"foo" "" ".*" ".*" \
+	".*" \
+	$test
+}
+
+continue_to_exception \
+    "CONSTRAINT_ERROR" \
+    "continue until CE caught by all-exceptions catchpoint"
+
+continue_to_exception \
+    "PROGRAM_ERROR" \
+    "continue until PE caught by all-exceptions catchpoint"
 
 ################################################
 # 2. Try catching only some of the exceptions. #