#107: Debugger "watchpoints": breakpoints that trigger when a command…

… executed matches a particular regex.

debug-test/Makefile

@@ -0,0 +1,12 @@
+
+# Run as ./make -f debug-test/Makefile -X --debugger-stop=preaction,
+# then do `watch Hell.`.
+
+UNEXPANDED=expanded
+
+all: test
+	echo "$(UNEXPANDED) all done!"
+
+test:
+	echo "$(UNEXPANDED) Hello"
+	echo "$(UNEXPANDED) Goodbye"

doc/readthedocs/debugger/commands/breakpoints/break.rst

@@ -37,4 +37,4 @@ Examples:
 
 .. seealso::
 
-   :ref:`delete <delete>`.
+   :ref:`delete <delete>`, :ref:`watch <watch>`.

doc/readthedocs/debugger/commands/breakpoints/watch.rst

@@ -0,0 +1,24 @@
+.. index:: watch
+.. _watch:
+
+Add a command watchpoint (`watch`)
+-------------------------------------
+
+**watch** *regex*
+
+Add a "command watch" breakpoint that triggers before a command that is about to be executed matches the given regex.
+An argument is the regex.
+
+Example:
+++++++++
+
+::
+
+    # 'watch' if something tries to delete "precious" directory
+    watch rm -[rf] precious
+    # Alternative regex
+    watch \brm\b.+precious
+
+.. seealso::
+
+   :ref:`delete <delete>`, :ref:`break <break>`.

libdebugger/Makefile.am

@@ -33,6 +33,7 @@ noinst_HEADERS = \
 	command/help/step.h \
 	command/help/target.h \
 	command/help/up.h \
+	command/help/watch.h \
 	command/help/where.h \
 	command/help/write.h \
 	file2line.h \
@@ -77,6 +78,7 @@ libdebugger_a_SOURCES =  \
 	command/step.c \
 	command/target.c \
 	command/up.c \
+	command/watch.c \
 	command/where.c \
 	command/write.c \
 	break.c \

libdebugger/break.c

@@ -20,18 +20,29 @@ Boston, MA 02111-1307, USA.  */
 /** debugger command stack routines. */
 
 #include <assert.h>
+#include <regex.h>
 #include "break.h"
+#include "cmd.h"
 #include "msg.h"
 #include "filedef.h"
 #include "print.h"
 
+enum breakpoint_type
+{
+  LINE,
+  COMMAND_WATCH
+};
+
 /*! Node for an item in the target call stack */
 struct breakpoint_node
 {
-  file_t            *p_target;
-  unsigned int      i_num;
-  brkpt_mask_t      brkpt_mask;
-  breakpoint_node_t *p_next;
+  enum breakpoint_type type;
+  file_t               *p_target;
+  unsigned int         i_num;
+  brkpt_mask_t         brkpt_mask;
+  regex_t              regex;
+  char                 *psz_text;
+  breakpoint_node_t    *p_next;
 };
 
 /** Pointers to top/bottom of current breakpoint target stack */
@@ -58,6 +69,7 @@ add_breakpoint (file_t *p_target, const brkpt_mask_t brkpt_mask)
     p_breakpoint_bottom->p_next = p_new;
   }
   p_breakpoint_bottom           = p_new;
+  p_new->type                   = LINE;
   p_new->p_target               = p_target;
   p_new->i_num                  = ++i_breakpoints;
   p_new->brkpt_mask             = brkpt_mask;
@@ -123,7 +135,13 @@ remove_breakpoint (unsigned int i, bool silent)
 
       if (p_prev) p_prev->p_next = p->p_next;
 
-      if (p->p_target->tracing) {
+      if (p->type == COMMAND_WATCH) {
+          dbg_msg(_("Command watchpoint %u cleared."), i);
+          regfree(&p->regex);
+          free(p->psz_text);
+          free(p);
+          return true;
+      } else if (p->p_target->tracing) {
 	p->p_target->tracing = BRK_NONE;
 	dbg_msg(_("Breakpoint %u on target `%s' cleared."),
 	       i, p->p_target->name);
@@ -156,17 +174,169 @@ list_breakpoints (void)
 
   dbg_msg(  "Num Type           Disp Enb Mask Target  Location");
   for (p = p_breakpoint_top; p; p = p->p_next) {
-    printf("%3u breakpoint     keep   y 0x%02x %s",
-	   p->i_num,
-	   p->brkpt_mask,
-           p->p_target->name);
-    if (p->p_target->floc.filenm) {
-	printf(" at ");
-	print_floc_prefix(&(p->p_target->floc));
+    if (p->type == LINE) {
+      printf("%3u breakpoint     keep   y 0x%02x %s",
+             p->i_num,
+             p->brkpt_mask,
+             p->p_target->name);
+      if (p->p_target->floc.filenm) {
+          printf(" at ");
+          print_floc_prefix(&(p->p_target->floc));
+      }
+    } else {
+      printf("%3u command watchpoint     %s", p->i_num, p->psz_text);
     }
     printf("\n");
   }
 }
+
+bool
+add_command_watchpoint(const char *psz_regex)
+{
+  int re_compile_status;
+  breakpoint_node_t *p_new   = CALLOC (breakpoint_node_t, 1);
+
+  if (!p_new) return false;
+
+  re_compile_status             = regcomp(&p_new->regex, psz_regex, REG_EXTENDED);
+
+  // Not sure if regex_t can be memmoved, so initializing it in the allocated breakpoint_node_t.
+  if (re_compile_status != 0) {
+    char reg_error_message[100];
+    regerror(re_compile_status, &p_new->regex, reg_error_message, sizeof(reg_error_message)-1);
+    dbg_msg("Could not compile regex: %s: %s", psz_regex, reg_error_message);
+    regfree(&p_new->regex);
+    free(p_new);
+    return false;
+  }
+
+  p_new->type                   = COMMAND_WATCH;
+  p_new->psz_text               = strdup(psz_regex);
+  p_new->i_num                  = ++i_breakpoints;
+  p_new->p_target               = NULL;
+  p_new->brkpt_mask             = 0;
+
+  /* Add breakpoint to list of breakpoints. */
+  if (!p_breakpoint_top) {
+    assert(!p_breakpoint_bottom);
+    p_breakpoint_top            = p_breakpoint_bottom = p_new;
+  } else {
+    p_breakpoint_bottom->p_next = p_new;
+  }
+  p_breakpoint_bottom           = p_new;
+
+  printf(_("Watchpoint %u for regex `%s' added\n"),
+         p_new->i_num, p_new->psz_text);
+  return true;
+}
+
+static size_t
+print_till_eol(const char *psz_line)
+{
+  int count = 0;
+  while (psz_line[count] != 0 && psz_line[count] != '\n') {
+    putchar(psz_line[count]);
+    count++;
+  }
+  return count;
+}
+
+static void
+print_underline(size_t offset, size_t length)
+{
+  printf ("%*s", (int) offset, "");
+  for (int i = 0; i < length; i++) {
+    putchar('^');
+  }
+  putchar('\n');
+}
+
+
+static void
+print_command_underlined(const char *psz_command, size_t sub_offset, size_t sub_length)
+{
+  int tail_length;
+  // TODO: Doesn't account for \t, \r.
+
+  do {
+    long line_length = print_till_eol(psz_command);
+    putchar('\n');
+    psz_command += line_length; // and a newline/null
+
+    if (*psz_command == '\n') {
+      psz_command++;
+    }
+
+    if (sub_offset < line_length) {
+      size_t underline_length = MIN(sub_length, line_length - sub_offset);
+      print_underline(sub_offset, underline_length);
+      break;
+    }
+
+    sub_offset -= line_length;
+
+    // Skip the newline
+    if (sub_offset == 0) {
+      // The offset can, in theory, start on newline.
+
+      sub_length--;
+      while (*psz_command == '\n') {
+        putchar('\n');
+        // If only \n-s need to be underlined, then underline the last of them.
+        if (sub_length == 1) {
+          puts ("^");
+          psz_command++;
+          break;
+        }
+        psz_command++;
+        sub_length--;
+      }
+
+    } else {
+      sub_offset--;
+    }
+
+  } while (*psz_command != '\0');
+
+  tail_length = printf("%s", psz_command) - 1;
+  if (tail_length > 0 && psz_command[tail_length] != '\n') {
+    putchar('\n');
+  }
+}
+
+
+static bool
+any_command_breakpoint_matches(const char *psz_expanded_command)
+{
+  breakpoint_node_t *p;
+  int match_status;
+
+  for (p = p_breakpoint_top; p; p = p->p_next) {
+    if (p->type == COMMAND_WATCH) {
+      regmatch_t pmatch;
+      match_status = regexec(&p->regex, psz_expanded_command, (size_t) 1, &pmatch, 0);
+      if (match_status == 0) {
+        // TODO: Determine which line of command it was, if it was multi-line.
+        printf (_("Command matched a watchpoint %u at (%d:%d) '%s':\n%s\n"),
+                p->i_num, (int) pmatch.rm_so, (int) pmatch.rm_eo, p->psz_text, psz_expanded_command);
+        print_command_underlined(psz_expanded_command, pmatch.rm_so, pmatch.rm_eo - pmatch.rm_so);
+        return true;
+      }
+    }
+  }
+
+  return false;
+}
+
+void
+check_command_watchpoint(target_stack_node_t *p_call_stack, file_t *p_target, const char *psz_expanded_command)
+{
+  if (any_command_breakpoint_matches (psz_expanded_command)) {
+    enter_debugger(p_call_stack, p_target, 0, DEBUG_WATCHPOINT);
+  }
+}
+
+
 /*
  * Local variables:
  * eval: (c-set-style "gnu")

libdebugger/break.h

@@ -26,6 +26,7 @@ Boston, MA 02111-1307, USA.  */
 #define DBG_BREAK_H
 
 #include "types.h"
+#include "trace.h"
 
 /*! Opaque type definition for an item in the breakpoint list. */
 typedef struct breakpoint_node breakpoint_node_t;
@@ -45,6 +46,11 @@ extern unsigned int i_breakpoints;
 */
 extern bool add_breakpoint (file_t *p_target, unsigned int brkp_mask);
 
+/*! Add "psz_regex" command watchpoint to the list of breakpoints.
+    Return true if there were no errors.
+*/
+extern bool add_command_watchpoint (const char *psz_regex);
+
 /*! Remove breakpoint i from the list of breakpoints. Return true if
     there were no errors. If silent is true, then don't warn about
     not finding breakpoint at "i".
@@ -54,4 +60,6 @@ extern bool remove_breakpoint (unsigned int i, bool silent);
 /*! List breakpoints.*/
 extern void list_breakpoints (void);
 
+extern void check_command_watchpoint (target_stack_node_t *p_call_stack, file_t *p_target, const char *psz_expanded_command);
+
 #endif /* DBG_BREAK_H */

libdebugger/cmd.c

@@ -264,8 +264,10 @@ debug_return_t enter_debugger (target_stack_node_t *p,
     if (!p_target->tracing) return continue_execution;
   } else if ( !debugger_on_error
 	      && !(i_debugger_stepping || i_debugger_nexting)
-	      && p_target && !p_target->tracing && -2 != errcode )
+	      && p_target && !p_target->tracing && -2 != errcode
+	      && reason != DEBUG_WATCHPOINT ) {
     return continue_execution;
+  }
 
   /* Clear temporary breakpoints. */
   if (p_target && p_target->tracing & BRK_TEMP)

libdebugger/cmd.h

@@ -69,6 +69,7 @@ extern debug_return_t dbg_cmd_help(char *psz_args);
 extern debug_return_t dbg_cmd_info(char *psz_args);
 extern debug_return_t dbg_cmd_target(char *psz_args);
 extern debug_return_t dbg_cmd_show(char *psz_args);
+extern debug_return_t dbg_cmd_watch(char *psz_regex);
 extern debug_return_t dbg_cmd_where(char *psz_args);
 extern debug_return_t dbg_cmd_set(char *psz_args);
 extern debug_return_t dbg_cmd_set_var (char *psz_arg, int expand);

libdebugger/cmd_initialize.h

@@ -54,6 +54,7 @@ Boston, MA 02111-1307, USA.  */
 #include "command/help/target.h"
 #include "command/help/up.h"
 #include "command/help/where.h"
+#include "command/help/watch.h"
 #include "command/help/write.h"
 
 /* A structure which contains information on the commands this program
@@ -90,6 +91,7 @@ long_cmd_t dbg_commands[] = {
   { "step"    , 's' },
   { "target"  , 't' },
   { "up"      , 'u' },
+  { "watch"   , 'W' },
   { "where"   , 'T' },
   { "write"   , 'w' },
   { (char *)NULL, ' '}
@@ -322,6 +324,13 @@ dbg_cmd_up_init(unsigned int c)
   short_command[c].use  = _("up [*amount*]");
 }
 
+static void
+dbg_cmd_watch_init(unsigned int c)
+{
+  short_command[c].func = &dbg_cmd_watch;
+  short_command[c].use =  _("watch");
+}
+
 static void
 dbg_cmd_where_init(unsigned int c)
 {
@@ -375,6 +384,7 @@ cmd_initialize(void)
   DBG_CMD_INIT(step, 's', true);
   DBG_CMD_INIT(target, 't', false);
   DBG_CMD_INIT(up, 'u', false);
+  DBG_CMD_INIT(watch, 'W', false);
   DBG_CMD_INIT(where, 'T', false);
   DBG_CMD_INIT(write, 'w', false);
 }

libdebugger/command/help/watch.h

@@ -0,0 +1,8 @@
+/** \file libdebugger/command/help/watch.h
+ *
+ *  \brief Help text for debugger command `watch`.
+ *
+ */
+#define watch_HELP_TEXT							\
+  "Add a \"command watch\" breakpoint that triggers when a command is about to be executed matches the given regex.\n"			\
+  "An argument is the regex."

libdebugger/command/info.c

@@ -279,6 +279,10 @@ dbg_cmd_info_program()
       printf(_("Program stopped from explicit debugger function call.\n"));
       printf("\n");
       break;
+    case DEBUG_WATCHPOINT:
+      printf(_("Program stopped at a command watchpoint.\n"));
+      printf("\n");
+      break;
     case DEBUG_NOT_GIVEN:
       printf(_("Reason not given.\n"));
       break;