[PATCH] [PR gdb/27393] set directories: handle empty dirs.

[Lancelot SIX via Gdb-patches <gdb-patches@sourceware.org>]

As reported in gdb/27393, the 'directory' and 'set directories' commands
fail when parsing an empty dir name:

    (gdb) set directories ""
    /home/lsix/dev/gnu/binutils-gdb/gdbsupport/pathstuff.cc:132: internal-error: gdb::unique_xmalloc_ptr<char> gdb_abspath(const char*): Assertion `path != NULL && path[0] != '\0'' failed.

or

    (gdb) dir :
    /home/lsix/dev/gnu/binutils-gdb/gdbsupport/pathstuff.cc:132: internal-error: gdb::unique_xmalloc_ptr<char> gdb_abspath(const char*): Assertion `path != NULL && path[0] != '\0'' failed.

This patch fixes this issue by ignoring any attempt to add an empty
name to the source directories list.  'set dir ""' will reset the
directories list the same way 'set dir' would do it.

Tested on x86_64.

gdb/ChangeLog:

	PR gdb/27393
	* source.c (add_path): Skip empty dirnames.

gdb/testsuite/ChangeLog:

	PR gdb/27393
	* gdb.base/source-dir.exp: Test that empty dirnames are skipped.
---
 gdb/source.c                          |  2 ++
 gdb/testsuite/gdb.base/source-dir.exp | 41 +++++++++++++++++++++++++++
 2 files changed, 43 insertions(+)

diff --git a/gdb/source.c b/gdb/source.c
index dc30dac6d78..3a8f829759b 100644
--- a/gdb/source.c
+++ b/gdb/source.c
@@ -572,6 +572,8 @@ add_path (const char *dirname, char **which_path, int parse_separators)
 	    break;
 	}
 
+      if (name[0] == '\0')
+        goto skip_dup;
       if (name[0] == '~')
 	new_name_holder.reset (tilde_expand (name));
 #ifdef HAVE_DOS_BASED_FILE_SYSTEM
diff --git a/gdb/testsuite/gdb.base/source-dir.exp b/gdb/testsuite/gdb.base/source-dir.exp
index 988ea59afb5..eff683199be 100644
--- a/gdb/testsuite/gdb.base/source-dir.exp
+++ b/gdb/testsuite/gdb.base/source-dir.exp
@@ -163,5 +163,46 @@ proc test_truncated_comp_dir {} {
 	"info source after setting directory search list"
 }
 
+proc test_change_search_directory_with_empty_dirname {} {
+    gdb_start
+
+    # Add 3 entries to the source directories list:
+    # - ""
+    # - "/foo"
+    # - "/bar"
+    # Since /foo and /bar probably do not exist, ignore the warnings printed by
+    # GDB.
+    if { [ishost *-*-mingw*] } {
+	gdb_test "set directories ;/foo;/bar" ".*"
+    } else {
+	gdb_test "set directories :/foo:/bar" ".*"
+    }
+
+    # The first entry added ("") should be ignored, only /foo and /bar are
+    # effectively added.
+    with_test_prefix "initial_directory_state" {
+	gdb_test "show directories" \
+	    [search_dir_list [list \
+				  "/foo" \
+				  "/bar" \
+				  "\\\$cdir" \
+				  "\\\$cwd"]]
+    }
+
+    # Arguments can be quoted.  Check a empty string has the same effect as
+    # 'set directory' (i.e. reset to $cdir:$cwd)
+    gdb_test_no_output "set directories \"\""
+
+    with_test_prefix "directory_after_reset" {
+	gdb_test "show directories" \
+	    [search_dir_list [list \
+				  "\\\$cdir" \
+				  "\\\$cwd"]]
+    }
+
+    gdb_exit
+}
+
 test_changing_search_directory
+test_change_search_directory_with_empty_dirname
 test_truncated_comp_dir
-- 
2.30.0