print-symbol-loading.exp: Allow libc symbols to be already loaded

One consequence of changing libpthread_name_p() in solib.c to (also)
match libc is that the symbols for libc will now be loaded by
solib_add() in solib.c.  I think this is mostly harmless because
we'll likely want these symbols to be loaded anyway, but it did cause
two failures in gdb.base/print-symbol-loading.exp.

Specifically...

1)

sharedlibrary .*
(gdb) PASS: gdb.base/print-symbol-loading.exp: shlib off: load shared-lib

now looks like this:

sharedlibrary .*
Symbols already loaded for /lib64/libc.so.6
(gdb) PASS: gdb.base/print-symbol-loading.exp: shlib off: load shared-lib

2)

sharedlibrary .*
Loading symbols for shared libraries: .*
(gdb) PASS: gdb.base/print-symbol-loading.exp: shlib brief: load shared-lib

now looks like this:

sharedlibrary .*
Loading symbols for shared libraries: .*
Symbols already loaded for /lib64/libc.so.6
(gdb) PASS: gdb.base/print-symbol-loading.exp: shlib brief: load shared-lib

Fixing case #2 ended up being easier than #1.  #1 had been using
gdb_test_no_output to correctly match this no-output case.  I
ended up replacing it with gdb_test_multiple, matching the exact
expected output for each of the two now acceptable cases.

For case #2, I simply added an optional non-capturing group
for the potential new output.

gdb/testsuite/ChangeLog:

	* gdb.base/print-symbol-loading.exp (proc test_load_shlib):
	Allow "Symbols already loaded for..." messages.

1 files changed, 12 insertions, 3 deletions

diff --git a/gdb/testsuite/gdb.base/print-symbol-loading.exp b/gdb/testsuite/gdb.base/print-symbol-loading.exp
index b8eb1c8..93ec43a 100644
--- a/gdb/testsuite/gdb.base/print-symbol-loading.exp
+++ b/gdb/testsuite/gdb.base/print-symbol-loading.exp
@@ -96,6 +96,7 @@ test_load_core full
 
 proc test_load_shlib { print_symbol_loading } {
     global binfile
+    global gdb_prompt
     with_test_prefix "shlib ${print_symbol_loading}" {
 	clean_restart ${binfile}
 	gdb_test_no_output "set auto-solib-add off"
@@ -106,12 +107,20 @@ proc test_load_shlib { print_symbol_loading } {
 	set test_name "load shared-lib"
 	switch ${print_symbol_loading} {
 	    "off" {
-		gdb_test_no_output "sharedlibrary .*" \
-		    ${test_name}
+		set cmd "sharedlibrary .*"
+		set cmd_regex [string_to_regexp $cmd]
+		gdb_test_multiple $cmd $test_name {
+		    -re "^$cmd_regex\r\n$gdb_prompt $" {
+			pass $test_name
+		    }
+		    -re "^$cmd_regex\r\nSymbols already loaded for\[^\r\n\]*\\/libc\\.\[^\r\n\]*\r\n$gdb_prompt $" {
+			pass $test_name
+		    }
+		}
 	    }
 	    "brief" {
 		gdb_test "sharedlibrary .*" \
-		    "Loading symbols for shared libraries: \\.\\*" \
+		    "Loading symbols for shared libraries: \\.\\*.*?(?:Symbols already loaded for .*?libc)?" \
 		    ${test_name}
 	    }
 	    "full" {