Add simple_search_memory unit tests

This adds some unit tests for simple_search_memory.  I tried here to
reproduce some bugs (PR gdb/11158 and PR gdb/17756), but was unable
to.

gdb/ChangeLog
2020-10-07  Tom Tromey  <tromey@adacore.com>

	* unittests/search-memory-selftests.c: New file.
	* Makefile.in (SELFTESTS_SRCS): Add
	unittests/search-memory-selftests.c.

3 files changed, 106 insertions, 0 deletions

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index ff6554d..3c9d07e 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,5 +1,11 @@
 2020-10-07  Tom Tromey  <tromey@adacore.com>
 
+	* unittests/search-memory-selftests.c: New file.
+	* Makefile.in (SELFTESTS_SRCS): Add
+	unittests/search-memory-selftests.c.
+
+2020-10-07  Tom Tromey  <tromey@adacore.com>
+
 	PR gdb/16930:
 	* findcmd.c (_initialize_mem_search): Mention that the range is
 	inclusive.
diff --git a/gdb/Makefile.in b/gdb/Makefile.in
index e14d41c..80b788c 100644
--- a/gdb/Makefile.in
+++ b/gdb/Makefile.in
@@ -458,6 +458,7 @@ SELFTESTS_SRCS = \
 	unittests/scoped_fd-selftests.c \
 	unittests/scoped_mmap-selftests.c \
 	unittests/scoped_restore-selftests.c \
+	unittests/search-memory-selftests.c \
 	unittests/string_view-selftests.c \
 	unittests/style-selftests.c \
 	unittests/tracepoint-selftests.c \
diff --git a/gdb/unittests/search-memory-selftests.c b/gdb/unittests/search-memory-selftests.c
new file mode 100644
index 0000000..5d2a1b9
--- /dev/null
+++ b/gdb/unittests/search-memory-selftests.c
@@ -0,0 +1,99 @@
+/* Self tests for simple_search_memory for GDB, the GNU debugger.
+
+   Copyright (C) 2020 Free Software Foundation, Inc.
+
+   This file is part of GDB.
+
+   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/>.  */
+
+#include "gdbsupport/common-defs.h"
+#include "gdbsupport/selftest.h"
+#include "gdbsupport/search.h"
+
+namespace selftests {
+namespace search_memory_tests {
+
+static void
+run_tests ()
+{
+  size_t size = 2 * SEARCH_CHUNK_SIZE + 1;
+
+  std::vector<gdb_byte> data (size);
+  data[size - 1] = 'x';
+
+  bool read_fully = false;
+  bool read_off_end = false;
+  auto read_memory = [&] (CORE_ADDR from, gdb_byte *out, size_t len)
+    {
+      if (from + len > data.size ())
+	read_off_end = true;
+      else
+	memcpy (out, &data[from], len);
+      if (from + len == data.size ())
+	read_fully = true;
+      return true;
+    };
+
+  gdb_byte pattern = 'x';
+
+  CORE_ADDR addr = 0;
+  int result = simple_search_memory (read_memory, 0, data.size (),
+				     &pattern, 1, &addr);
+  /* In this case we don't care if read_fully was set or not.  */
+  SELF_CHECK (result == 1);
+  SELF_CHECK (!read_off_end);
+  SELF_CHECK (addr == size - 1);
+
+  addr = 0;
+  read_fully = false;
+  read_off_end = false;
+  pattern = 'q';
+  result = simple_search_memory (read_memory, 0, data.size (),
+				 &pattern, 1, &addr);
+  SELF_CHECK (result == 0);
+  SELF_CHECK (!read_off_end);
+  SELF_CHECK (read_fully);
+  SELF_CHECK (addr == 0);
+
+  /* Setup from PR gdb/17756.  */
+  size = 0x7bb00;
+  data = std::vector<gdb_byte> (size);
+  const CORE_ADDR base_addr = 0x08370000;
+  const gdb_byte wpattern[] = { 0x90, 0x8b, 0x98, 0x8 };
+  const CORE_ADDR found_addr = 0x837bac8;
+  memcpy (&data[found_addr - base_addr], wpattern, sizeof (wpattern));
+
+  auto read_memory_2 = [&] (CORE_ADDR from, gdb_byte *out, size_t len)
+    {
+      memcpy (out, &data[from - base_addr], len);
+      return true;
+    };
+
+  result = simple_search_memory (read_memory_2, base_addr, data.size (),
+				 wpattern, sizeof (wpattern), &addr);
+  SELF_CHECK (result == 1);
+  SELF_CHECK (addr == found_addr);
+}
+
+} /* namespace search_memory_tests */
+} /* namespace selftests */
+
+
+void _initialize_search_memory_selftests ();
+void
+_initialize_search_memory_selftests ()
+{
+  selftests::register_test ("search_memory",
+			    selftests::search_memory_tests::run_tests);
+}