patch 8.1.0091: MS-Windows: Cannot interrupt gdb when program is running

Problem:    MS-Windows: Cannot interrupt gdb when program is running.
Solution:   Add debugbreak() and use it in the terminal debugger.
            Respect 'modified' in a prompt buffer.

runtime/doc/eval.txt

@@ -2108,6 +2108,7 @@ cscope_connection([{num}, {dbpath} [, {prepend}]])
 cursor({lnum}, {col} [, {off}])
 				Number	move cursor to {lnum}, {col}, {off}
 cursor({list})			Number	move cursor to position in {list}
+debugbreak({pid})		Number  interrupt process being debugged
 deepcopy({expr} [, {noref}])	any	make a full copy of {expr}
 delete({fname} [, {flags}])	Number	delete the file or directory {fname}
 deletebufline({expr}, {first}[, {last}])
@@ -3480,6 +3481,11 @@ cursor({list})
 		position within a <Tab> or after the last character.
 		Returns 0 when the position could be set, -1 otherwise.
 
+debugbreak({pid})					*debugbreak()*
+		Specifically used to interrupt a program being debugged.  It
+		will cause process {pid} to get a SIGTRAP.  Behavior for other
+		processes is undefined. See |terminal-debugger|.
+		{only available on MS-Windows}
 
 deepcopy({expr} [, {noref}])				*deepcopy()* *E698*
 		Make a copy of {expr}.  For Numbers and Strings this isn't

runtime/pack/dist/opt/termdebug/plugin/termdebug.vim

@@ -98,6 +98,7 @@ func s:StartDebug_internal(dict)
     return
   endif
   let s:ptywin = 0
+  let s:pid = 0
 
   " Uncomment this line to write logging in "debuglog".
   " call ch_logfile('debuglog', 'w')
@@ -271,6 +272,8 @@ func s:StartDebug_prompt(dict)
     exe 'bwipe! ' . s:promptbuf
     return
   endif
+  " Mark the buffer modified so that it's not easy to close.
+  set modified
   let s:gdb_channel = job_getchannel(s:gdbjob)  
 
   " Interpret commands while the target is running.  This should usualy only
@@ -396,10 +399,16 @@ func s:PromptCallback(text)
   call s:SendCommand(a:text)
 endfunc
 
-" Function called when pressing CTRL-C in the prompt buffer.
+" Function called when pressing CTRL-C in the prompt buffer and when placing a
+" breakpoint.
 func s:PromptInterrupt()
-  call ch_log('Interrupting gdb')
-  call job_stop(s:gdbjob, 'int')
+  if s:pid == 0
+    echoerr 'Cannot interrupt gdb, did not find a process ID'
+  else
+    call ch_log('Interrupting gdb')
+    " Using job_stop(s:gdbjob, 'int') does not work.
+    call debugbreak(s:pid)
+  endif
 endfunc
 
 " Function called when gdb outputs text.
@@ -430,7 +439,7 @@ func s:GdbOutCallback(channel, text)
 
   " Add the output above the current prompt.
   call append(line('$') - 1, text)
-  set nomodified
+  set modified
 
   call win_gotoid(curwinid)
 endfunc
@@ -509,6 +518,7 @@ endfunc
 func s:EndPromptDebug(job, status)
   let curwinid = win_getid(winnr())
   call win_gotoid(s:gdbwin)
+  set nomodified
   close
   if curwinid != s:gdbwin
     call win_gotoid(curwinid)
@@ -535,6 +545,8 @@ func s:CommOutput(chan, msg)
 	call s:HandleNewBreakpoint(msg)
       elseif msg =~ '^=breakpoint-deleted,'
 	call s:HandleBreakpointDelete(msg)
+      elseif msg =~ '^=thread-group-started'
+	call s:HandleProgramRun(msg)
       elseif msg =~ '^\^done,value='
 	call s:HandleEvaluate(msg)
       elseif msg =~ '^\^error,msg='
@@ -655,7 +667,7 @@ func s:DeleteCommands()
   for val in s:BreakpointSigns
     exe "sign undefine debugBreakpoint" . val
   endfor
-  unlet s:BreakpointSigns
+  let s:BreakpointSigns = []
 endfunc
 
 " :Break - Set a breakpoint at the cursor position.
@@ -666,9 +678,7 @@ func s:SetBreakpoint()
   if !s:stopped
     let do_continue = 1
     if s:way == 'prompt'
-      " Need to send a signal to get the UI to listen.  Strangely this is only
-      " needed once.
-      call job_stop(s:gdbjob, 'int')
+      call s:PromptInterrupt()
     else
       call s:SendCommand('-exec-interrupt')
     endif
@@ -798,13 +808,13 @@ func s:HandleCursor(msg)
   let wid = win_getid(winnr())
 
   if a:msg =~ '^\*stopped'
+    call ch_log('program stopped')
     let s:stopped = 1
   elseif a:msg =~ '^\*running'
+    call ch_log('program running')
     let s:stopped = 0
   endif
 
-  call s:GotoSourcewinOrCreateIt()
-
   if a:msg =~ 'fullname='
     let fname = s:GetFullname(a:msg)
   else
@@ -813,6 +823,7 @@ func s:HandleCursor(msg)
   if a:msg =~ '^\(\*stopped\|=thread-selected\)' && filereadable(fname)
     let lnum = substitute(a:msg, '.*line="\([^"]*\)".*', '\1', '')
     if lnum =~ '^[0-9]*$'
+    call s:GotoSourcewinOrCreateIt()
       if expand('%:p') != fnamemodify(fname, ':p')
 	if &modified
 	  " TODO: find existing window
@@ -828,7 +839,7 @@ func s:HandleCursor(msg)
       exe 'sign place ' . s:pc_id . ' line=' . lnum . ' name=debugPC file=' . fname
       setlocal signcolumn=yes
     endif
-  else
+  elseif !s:stopped || fname != ''
     exe 'sign unplace ' . s:pc_id
   endif
 
@@ -892,6 +903,17 @@ func s:HandleBreakpointDelete(msg)
   endif
 endfunc
 
+" Handle the debugged program starting to run.
+" Will store the process ID in s:pid
+func s:HandleProgramRun(msg)
+  let nr = substitute(a:msg, '.*pid="\([0-9]*\)\".*', '\1', '') + 0
+  if nr == 0
+    return
+  endif
+  let s:pid = nr
+  call ch_log('Detected process ID: ' . s:pid)
+endfunc
+
 " Handle a BufRead autocommand event: place any signs.
 func s:BufRead()
   let fname = expand('<afile>:p')

src/evalfunc.c

@@ -123,6 +123,9 @@ static void f_cosh(typval_T *argvars, typval_T *rettv);
 static void f_count(typval_T *argvars, typval_T *rettv);
 static void f_cscope_connection(typval_T *argvars, typval_T *rettv);
 static void f_cursor(typval_T *argsvars, typval_T *rettv);
+#ifdef WIN3264
+static void f_debugbreak(typval_T *argvars, typval_T *rettv);
+#endif
 static void f_deepcopy(typval_T *argvars, typval_T *rettv);
 static void f_delete(typval_T *argvars, typval_T *rettv);
 static void f_deletebufline(typval_T *argvars, typval_T *rettv);
@@ -577,6 +580,9 @@ static struct fst
     {"count",		2, 4, f_count},
     {"cscope_connection",0,3, f_cscope_connection},
     {"cursor",		1, 3, f_cursor},
+#ifdef WIN3264
+    {"debugbreak",	1, 1, f_debugbreak},
+#endif
     {"deepcopy",	1, 2, f_deepcopy},
     {"delete",		1, 2, f_delete},
     {"deletebufline",	2, 3, f_deletebufline},
@@ -2761,6 +2767,33 @@ f_cursor(typval_T *argvars, typval_T *rettv)
     rettv->vval.v_number = 0;
 }
 
+#ifdef WIN3264
+/*
+ * "debugbreak()" function
+ */
+    static void
+f_debugbreak(typval_T *argvars, typval_T *rettv)
+{
+    int		pid;
+
+    rettv->vval.v_number = FAIL;
+    pid = (int)get_tv_number(&argvars[0]);
+    if (pid == 0)
+	EMSG(_(e_invarg));
+    else
+    {
+	HANDLE hProcess = OpenProcess(PROCESS_ALL_ACCESS, 0, pid);
+
+	if (hProcess != NULL)
+	{
+	    DebugBreakProcess(hProcess);
+	    CloseHandle(hProcess);
+	    rettv->vval.v_number = OK;
+	}
+    }
+}
+#endif
+
 /*
  * "deepcopy()" function
  */

src/undo.c

@@ -3539,7 +3539,9 @@ bufIsChanged(buf_T *buf)
     int
 bufIsChangedNotTerm(buf_T *buf)
 {
-    return !bt_dontwrite(buf)
+    // In a "prompt" buffer we do respect 'modified', so that we can control
+    // closing the window by setting or resetting that option.
+    return (!bt_dontwrite(buf) || bt_prompt(buf))
 	&& (buf->b_changed || file_ff_differs(buf, TRUE));
 }
 

src/version.c

@@ -761,6 +761,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    91,
 /**/
     90,
 /**/