[PR gdb/27614] gdb-add-index fails on symlinks.

PR 27614 shows that gdb-add-index fails to generate the index when its
argument is a symlink.

The following one liner illustrates the reported problem:

        $ echo 'int main(){}'|gcc -g -x c -;ln -s a.out symlink;gdb-add-index symlink
        gdb-add-index: No index was created for symlink
        gdb-add-index: [Was there no debuginfo? Was there already an index?]
        $ ls -l
        -rwxr-xr-x 1 25712 Mar 19 23:05 a.out*
        -rw------- 1  8277 Mar 19 23:05 a.out.gdb-index
        lrwxrwxrwx 1     5 Mar 19 23:05 symlink -> a.out*

GDB generates the .gdb-index file with a name that matches the name of
the actual program (a.out.gdb-index here), not the symlink that
references it.  The remaining of the script is looking for a file named
after the provided argument (would be 'symlink.gdb-index' in our
example).

gdb/ChangeLog:

	PR gdb/27614
	* contrib/gdb-add-index.sh: Fix when called with a symlink as an
	argument.

gdb/testsuite/ChangeLog:

	PR gdb/27614
	* gdb.dwarf2/gdb-add-index-symlink.exp: New test.

2 files changed, 52 insertions, 0 deletions

diff --git a/gdb/testsuite/ChangeLog b/gdb/testsuite/ChangeLog
index b3a41bd..c188719 100644
--- a/gdb/testsuite/ChangeLog
+++ b/gdb/testsuite/ChangeLog
@@ -1,3 +1,8 @@
+2021-05-10  Lancelot Six  <lsix@lancelotsix.com>
+
+	PR gdb/27614
+	* gdb.dwarf2/gdb-add-index-symlink.exp: New test.
+
 2021-05-10  Andrew Burgess  <andrew.burgess@embecosm.com>
 
 	* gdb.guile/guile.exp: Don't use the source directory as a
diff --git a/gdb/testsuite/gdb.dwarf2/gdb-add-index-symlink.exp b/gdb/testsuite/gdb.dwarf2/gdb-add-index-symlink.exp
new file mode 100644
index 0000000..eaeddec
--- /dev/null
+++ b/gdb/testsuite/gdb.dwarf2/gdb-add-index-symlink.exp
@@ -0,0 +1,47 @@
+# Copyright 2021 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/>.
+
+load_lib dwarf.exp
+
+# This test can only be run on targets which support DWARF-2.
+if {![dwarf2_support]} {
+    return 0
+}
+
+standard_testfile main.c
+
+if { [prepare_for_testing "failed to prepare" "${testfile}" \
+	  [list ${srcfile}]] } {
+    return -1
+}
+
+set symlink [file dirname $binfile]/symlink
+
+if { ![file exists $symlink] } {
+    file link -symbolic $symlink $binfile
+}
+
+if { [ensure_gdb_index $symlink] == -1 } {
+    fail "Unable to call gdb-add-index with a symlink to a symfile"
+    return -1
+}
+
+# Ok, we have a copy of $binfile with an index.
+# Restart gdb and verify the index was used.
+
+clean_restart $symlink
+gdb_test "mt print objfiles ${testfile}" \
+    "(gdb_index|debug_names).*" \
+    "index used"