[gdb/symtab] Fix language of duplicate static minimal symbol

Consider a test-case with source files msym.c:
...
static int foo (void) { return 1; }
...
and msym_main.c:
...
static int foo (void) { return 2; }
int main (void) { return 0; }
..
compiled as c++ with minimal symbols:
...
$ g++ msym_main.c msym.c
...

With objdump -x we find the two foo symbols prefixed with their corresponding
files in the symbol table:
...
0000000000000000 l    df *ABS*  0000000000000000              msym_main.c
00000000004004c7 l     F .text  000000000000000b              _ZL3foov
0000000000000000 l    df *ABS*  0000000000000000              msym.c
00000000004004dd l     F .text  000000000000000b              _ZL3foov
...

However, when we use gdb to print info on foo, both foos are listed, but we
get one symbol mangled and one symbol demangled:
...
$ gdb ./a.out -batch -ex "info func foo"
All functions matching regular expression "foo":

Non-debugging symbols:
0x00000000004004c7  foo()
0x00000000004004dd  _ZL3foov
...

During minimal symbol reading symbol_set_names is called for each symbol.

First, it's called with foo from msym.c, an entry is created in
per_bfd->demangled_names_hash and symbol_find_demangled_name is called, which
has the side effect of setting the language of the symbol to language_cplus.

Then, it's called with foo from msym_main.c.  Since
per_bfd->demangled_names_hash already has an entry for that name,
symbol_find_demangled_name is not called, and the language of the symbol
remains language_auto.

Fix this by doing the symbol_find_demangled_name call unconditionally.

Build and reg-tested on x86_64-linux.

gdb/ChangeLog:

2018-11-09  Tom de Vries  <tdevries@suse.de>

	* symtab.c (symbol_set_names): Call symbol_find_demangled_name
	unconditionally, to set the language of the symbol.  Manage freeing
	returned pointer using gdb::unique_xmalloc_ptr.

gdb/testsuite/ChangeLog:

2018-11-09  Tom de Vries  <tdevries@suse.de>

	* gdb.base/msym-lang.c: New test.
	* gdb.base/msym-lang.exp: New file.
	* gdb.base/msym-lang-main.c: New test.

4 files changed, 81 insertions, 0 deletions

diff --git a/gdb/testsuite/ChangeLog b/gdb/testsuite/ChangeLog
index a0e614f..015028c 100644
--- a/gdb/testsuite/ChangeLog
+++ b/gdb/testsuite/ChangeLog
@@ -1,3 +1,9 @@
+2018-11-09  Tom de Vries  <tdevries@suse.de>
+
+	* gdb.base/msym-lang.c: New test.
+	* gdb.base/msym-lang.exp: New file.
+	* gdb.base/msym-lang-main.c: New test.
+
 2018-11-08  Tom Tromey  <tom@tromey.com>
 
 	PR gdb/23555:
diff --git a/gdb/testsuite/gdb.base/msym-lang-main.c b/gdb/testsuite/gdb.base/msym-lang-main.c
new file mode 100644
index 0000000..f093f71
--- /dev/null
+++ b/gdb/testsuite/gdb.base/msym-lang-main.c
@@ -0,0 +1,28 @@
+/* This testcase is part of GDB, the GNU debugger.
+
+   Copyright 2018 Free Software Foundation, Inc.
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
+
+static int
+foo (void)
+{
+  return 2;
+}
+
+int
+main (void)
+{
+  return 0;
+}
diff --git a/gdb/testsuite/gdb.base/msym-lang.c b/gdb/testsuite/gdb.base/msym-lang.c
new file mode 100644
index 0000000..c961015
--- /dev/null
+++ b/gdb/testsuite/gdb.base/msym-lang.c
@@ -0,0 +1,22 @@
+/* This testcase is part of GDB, the GNU debugger.
+
+   Copyright 2018 Free Software Foundation, Inc.
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
+
+static int
+foo (void)
+{
+  return 1;
+}
diff --git a/gdb/testsuite/gdb.base/msym-lang.exp b/gdb/testsuite/gdb.base/msym-lang.exp
new file mode 100644
index 0000000..993225c
--- /dev/null
+++ b/gdb/testsuite/gdb.base/msym-lang.exp
@@ -0,0 +1,25 @@
+# Copyright (C) 2018 Free Software Foundation, Inc.
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+standard_testfile msym-lang-main.c msym-lang.c
+
+if {[prepare_for_testing "failed to prepare" $testfile [list $srcfile $srcfile2] \
+	 {c++}]} {
+    return -1
+}
+
+clean_restart ${testfile}
+
+gdb_test "info func foo" ".* foo\\(\\).* foo\\(\\).*"