Merge forward-search/reverse-search, use gdb::def_vector, remove limit

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 commit 85ae1317add94adef4817927e89cff80b92813dd
 Author:     Stan Shebs <shebs@codesourcery.com>
 AuthorDate: Thu Dec 8 02:27:47 1994 +0000

	     * source.c: Various cosmetic changes.
	     (forward_search_command): Handle very long source lines correctly.

a buffer with a hard limit was converted to a heap buffer:

  @@ -1228,15 +1284,26 @@ forward_search_command (regex, from_tty)
     stream = fdopen (desc, FOPEN_RT);
     clearerr (stream);
     while (1) {
  -/* FIXME!!!  We walk right off the end of buf if we get a long line!!! */
  -    char buf[4096];            /* Should be reasonable??? */
  -    register char *p = buf;
  +    static char *buf = NULL;
  +    register char *p;
  +    int cursize, newsize;
  +
  +    cursize = 256;
  +    buf = xmalloc (cursize);
  +    p = buf;

However, reverse_search_command has the exact same problem, and that
wasn't fixed.  We still have that "we walk right off" comment...

Recently, the xmalloc above was replaced with a xrealloc, because as
can be seen above, that 'buf' variable above was a static local,
otherwise we'd be leaking.  This commit replaces that and the
associated manual buffer growing with a gdb::def_vector<char>.  I
don't think there's much point in reusing the buffer across command
invocations.

While doing this, I realized that reverse_search_command is almost
identical to forward_search_command.  So this commit factors out a
common helper function instead of duplicating a lot of code.

There are some tests for "forward-search" in gdb.base/list.exp, but
since they use the "search" alias, they were a bit harder to find than
expected.  That's now fixed, both by testing both variants, and by
adding some commentary.  Also, there are no tests for the
"reverse-search" command, so this commit adds some for that too.

gdb/ChangeLog:
2018-12-08  Pedro Alves  <palves@redhat.com>

	* source.c (forward_search_command): Rename to ...
	(search_command_helper): ... this.  Add 'forward' parameter.
	Tweak to use a gdb::def_vector<char> instead of a xrealloc'ed
	buffer.  Handle backward searches too.
	(forward_search_command, reverse_search_command): Reimplement by
	calling search_command_helper.

gdb/testsuite/ChangeLog:
2018-12-08  Pedro Alves  <palves@redhat.com>

	* gdb.base/list.exp (test_forward_search): Rename to ...
	(test_forward_reverse_search): ... this.  Also test reverse-search
	and the forward-search alias.

2 files changed, 21 insertions, 2 deletions

diff --git a/gdb/testsuite/ChangeLog b/gdb/testsuite/ChangeLog
index 66310d7..b6c6c4a 100644
--- a/gdb/testsuite/ChangeLog
+++ b/gdb/testsuite/ChangeLog
@@ -1,3 +1,9 @@
+2018-12-08  Pedro Alves  <palves@redhat.com>
+
+	* gdb.base/list.exp (test_forward_search): Rename to ...
+	(test_forward_reverse_search): ... this.  Also test reverse-search
+	and the forward-search alias.
+
 2018-12-05  Andrew Burgess  <andrew.burgess@embecosm.com>
 
 	* config/sim.exp (gdb_target_sim): Remove redundant adjustment of
diff --git a/gdb/testsuite/gdb.base/list.exp b/gdb/testsuite/gdb.base/list.exp
index abfb0e1..9b172e9 100644
--- a/gdb/testsuite/gdb.base/list.exp
+++ b/gdb/testsuite/gdb.base/list.exp
@@ -485,7 +485,9 @@ proc test_list_filename_and_function {} {
 
 }
 
-proc test_forward_search {} {
+# Test the forward-search (aka search) and the reverse-search commands.
+
+proc test_forward_reverse_search {} {
 	global timeout
 
 	gdb_test_no_output "set listsize 4"
@@ -499,6 +501,17 @@ proc test_forward_search {} {
 
 	gdb_test "search 6789" "28\[ \t\]+oof .6789.;"
 
+	# Try again, we shouldn't re-find the same source line.  Also,
+	# while at it, test using the "forward-search" alias.
+	gdb_test "forward-search 6789" " not found"
+
+	# Now test backwards.  First make sure we start searching from
+	# the previous line, not the current line.
+	gdb_test "reverse-search 6789" " not found"
+
+	# Now find something in a previous line.
+	gdb_test "reverse-search 67" "26\[ \t\]+oof .67.;"
+
 	# Test that GDB won't crash if the line being searched is extremely long.
 
 	set oldtimeout $timeout
@@ -553,7 +566,7 @@ if [ set_listsize 10 ] then {
     test_repeat_list_command
     test_list_range
     test_list_filename_and_function
-    test_forward_search
+    test_forward_reverse_search
     test_only_end
     test_list_invalid_args
 }