debugger: implement printx command to evaluate filterx expressions

Signed-off-by: Balazs Scheidler <balazs.scheidler@axoflow.com>

lib/debugger/cmd-help.c

@@ -36,6 +36,7 @@ _cmd_help(Debugger *self, gint argc, gchar *argv[])
          "  info                     Display information about the current execution state\n"
          "  list or l                Display source code at the current location\n"
          "  print or p               Print the current log message using a template\n"
+         "  printx or px             Print the current log message using a filterx expression\n"
          "  drop or d                Drop the current message\n"
          "  quit or q                Tell syslog-ng to exit\n"
         );

lib/debugger/cmd-printx.c

@@ -0,0 +1,103 @@
+/*
+ * Copyright (c) 2024 Balázs Scheidler <balazs.scheidler@axoflow.com>
+ * Copyright (c) 2024 Axoflow
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library 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
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
+ *
+ * As an additional exemption you are allowed to compile & link against the
+ * OpenSSL libraries as published by the OpenSSL project. See the file
+ * COPYING for details.
+ *
+ */
+
+#include "filterx/filterx-parser.h"
+
+static void
+_eval_filterx_expr(Debugger *self, GList *list_of_exprs, LogMessage *msg)
+{
+  NVTable *payload = nv_table_ref(msg->payload);
+
+  gint expr_index = 1;
+  for (GList *l = list_of_exprs; l; l = l->next)
+    {
+      FilterXExpr *expr = (FilterXExpr *) l->data;
+      FilterXObject *res = filterx_expr_eval(expr);
+
+      if (!res)
+        {
+          printf("$%d = error(%s)\n", expr_index, filterx_eval_get_last_error());
+          filterx_eval_clear_errors();
+          goto fail;
+        }
+
+      GString *buf = scratch_buffers_alloc();
+      if (!filterx_object_repr(res, buf))
+        {
+          LogMessageValueType t;
+          if (!filterx_object_marshal(res, buf, &t))
+            g_assert_not_reached();
+        }
+      printf("$%d = %s\n", expr_index, buf->str);
+
+      filterx_object_unref(res);
+      expr_index++;
+    }
+
+fail:
+  nv_table_unref(payload);
+}
+
+static void
+_display_filterx_expr(Debugger *self, gint argc, gchar *argv[])
+{
+  GList *list_of_exprs = NULL;
+  for (gint i = 0; i < argc; i++)
+    {
+      gchar *expr_text = g_strdup_printf("%s;", argv[i]);
+      CfgLexer *lexer = cfg_lexer_new_buffer(self->cfg, expr_text, strlen(expr_text));
+
+      GList *partial = NULL;
+      if (!cfg_run_parser(self->cfg, lexer, &filterx_parser, (gpointer *) &partial, NULL) ||
+          !partial)
+        {
+          printf("Error parsing filterx expression: %s\n", expr_text);
+          g_free(expr_text);
+          goto exit;
+        }
+      g_free(expr_text);
+      list_of_exprs = g_list_concat(list_of_exprs, partial);
+    }
+  _eval_filterx_expr(self,
+                     list_of_exprs,
+                     self->breakpoint_site->msg);
+
+exit:
+  g_list_free_full(list_of_exprs, (GDestroyNotify) filterx_expr_unref);
+}
+
+static gboolean
+_cmd_printx(Debugger *self, gint argc, gchar *argv[])
+{
+  if (argc == 1)
+    {
+      gchar *vars[] = { "vars();", NULL };
+      _display_filterx_expr(self, 1, vars);
+    }
+  else
+    {
+      _display_filterx_expr(self, argc - 1, &argv[1]);
+    }
+  return TRUE;
+}

lib/debugger/debugger.c

@@ -145,6 +145,7 @@ _set_mode(Debugger *self, DebuggerMode new_mode, gboolean trace_message)
 
 #include "cmd-help.c"
 #include "cmd-print.c"
+#include "cmd-printx.c"
 #include "cmd-display.c"
 #include "cmd-drop.c"
 #include "cmd-info.c"
@@ -175,6 +176,8 @@ struct
   { "f",        _cmd_follow, .requires_breakpoint_site = TRUE },
   { "print",    _cmd_print, .requires_breakpoint_site = TRUE },
   { "p",        _cmd_print, .requires_breakpoint_site = TRUE },
+  { "printx",   _cmd_printx, .requires_breakpoint_site = TRUE },
+  { "px",       _cmd_printx, .requires_breakpoint_site = TRUE },
   { "list",     _cmd_list, },
   { "l",        _cmd_list, },
   { "display",  _cmd_display },
@@ -230,6 +233,43 @@ _fetch_command(Debugger *self)
   g_free(command);
 }
 
+static void
+_setup_filterx_context(Debugger *self, FilterXEvalContext *context)
+{
+  const LogPathOptions *path_options = self->breakpoint_site->path_options;
+  if (!path_options->filterx_context)
+    {
+      /* no parent context, let's use our own, changes to variables will be
+       * lost by the time we reach the very first filterx block, but we do
+       * allow setting variables in the context of the debugger */
+
+      filterx_eval_init_context(context, path_options->filterx_context);
+      context->msgs = &self->breakpoint_site->msg;
+      context->num_msg = 1;
+    }
+  else
+    {
+      filterx_eval_set_context(path_options->filterx_context);
+    }
+}
+
+static void
+_clear_filterx_context(Debugger *self, FilterXEvalContext *context)
+{
+  const LogPathOptions *path_options = self->breakpoint_site->path_options;
+  if (!path_options->filterx_context)
+    {
+      if (filterx_scope_is_dirty(context->scope))
+        {
+          printf("Dropping variables set from the debugger, as debugger was invoked before the filterx block\n");
+        }
+      filterx_eval_deinit_context(context);
+    }
+  else
+    filterx_eval_set_context(NULL);
+}
+
+
 static gboolean
 _handle_command(Debugger *self)
 {
@@ -289,6 +329,11 @@ _handle_interactive_prompt(Debugger *self)
       _set_current_location(self, NULL);
       printf("  Stopping on Interrupt...\n");
     }
+
+  FilterXEvalContext temporary_context;
+  if (self->breakpoint_site)
+    _setup_filterx_context(self, &temporary_context);
+
   while (1)
     {
       _fetch_command(self);
@@ -297,6 +342,8 @@ _handle_interactive_prompt(Debugger *self)
         break;
 
     }
+  if (self->breakpoint_site)
+    _clear_filterx_context(self, &temporary_context);
   printf("(continuing)\n");
 }