vim-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.
4551c0a9fc

runtime/doc/eval.txt

@@ -2084,6 +2084,7 @@ ctxsize()			Number	return |context-stack| size
 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}])
@@ -3641,6 +3642,11 @@ exp({expr})						*exp()*
 			:echo exp(-1)
 <			0.367879
 
+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|.
+		{Sends a SIGINT to a process {pid} other than MS-Windows}
 
 expand({expr} [, {nosuf} [, {list}]])				*expand()*
 		Expand wildcards and the following special keywords in {expr}.

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

@@ -462,10 +462,16 @@ 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 system('kill -SIGINT ' . s:pid)
+  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.
@@ -691,7 +697,11 @@ func s:SetBreakpoint()
   let do_continue = 0
   if !s:stopped
     let do_continue = 1
-    call s:SendCommand('-exec-interrupt')
+    if s:way == 'prompt'
+      call s:PromptInterrupt()
+    else
+      call s:SendCommand('-exec-interrupt')
+    endif
     sleep 10m
   endif
   " Use the fname:lnum format, older gdb can't handle --source.