Re: [PATCH] An implementation of pipe to make I/O communication between gdb and shell. [MinGW question]

[Abhijit Halder <abhijit dot k dot halder at gmail dot com>]

On Mon, Aug 15, 2011 at 1:25 AM, Jan Kratochvil
<jan.kratochvil@redhat.com> wrote:
> On Sun, 14 Aug 2011 21:41:57 +0200, Eli Zaretskii wrote:
>> > Abhijit Halder has suggested the suggested
>> > ? ? const char *argv[] = { "sh", "-c", "cat >/dev/null", NULL };
>> > ? ? pex_run (pipe->pex, PEX_LAST, "/bin/sh", argv, NULL, NULL, &status);
>> > works on UNIX but it will probably not work on MinGW as there is no "/bin/sh",
>> > is it?
>>
>> The file name of the shell, the "-c" switch, and the null device
>> should all be system-dependent. ?For MinGW, they should be,
>> respectively, "cmd.exe", "/c", and "nul".
>
> "cat >/dev/null" itself is user-entered command so that part is OK to be
> non-cross-platform (therefore also "nul" is not valid).
>
> OK, "cmd.exe" with "/c" seems easy enough.
>
>
>> > The current implementation:
>> > ? ? const char *argv[] = { "cat", ">/dev/null", NULL };
>> > ? ? pex_run (pipe->pex, PEX_SEARCH | PEX_LAST, "cat", argv, NULL, NULL, &status);
>> > produces that - therefore not working on UNIX:
>> > ? ? cat: >/dev/null: No such file or directory
>>
>> How hard is it to parse the redirection characters?
>
> Very, >, >>, &>, >&, &>>, x>&y, x>&y-, x<>y, many more.
>
>
> Thanks,
> Jan
>

Corrected the pattern matching code and added code to take care MinGW.

Working on testcase and doc part.

diff -rup src/gdb/Makefile.in dst/gdb/Makefile.in
--- src/gdb/Makefile.in	2011-07-27 23:55:26.000000000 +0530
+++ dst/gdb/Makefile.in	2011-08-14 07:31:15.802233004 +0530
@@ -713,7 +713,7 @@ SFILES = ada-exp.y ada-lang.c ada-typepr
 	objc-exp.y objc-lang.c \
 	objfiles.c osabi.c observer.c osdata.c \
 	opencl-lang.c \
-	p-exp.y p-lang.c p-typeprint.c p-valprint.c parse.c printcmd.c \
+	p-exp.y p-lang.c p-typeprint.c p-valprint.c parse.c pipe.c printcmd.c \
 	proc-service.list progspace.c \
 	prologue-value.c psymtab.c \
 	regcache.c reggroups.c remote.c remote-fileio.c reverse.c \
@@ -870,7 +870,7 @@ COMMON_OBS = $(DEPFILES) $(CONFIG_OBS) $
 	mi-common.o \
 	event-loop.o event-top.o inf-loop.o completer.o \
 	gdbarch.o arch-utils.o gdbtypes.o osabi.o copying.o \
-	memattr.o mem-break.o target.o parse.o language.o buildsym.o \
+	memattr.o mem-break.o target.o parse.o pipe.o language.o buildsym.o \
 	findcmd.o \
 	std-regs.o \
 	signals.o \
diff -rup src/gdb/NEWS dst/gdb/NEWS
--- src/gdb/NEWS	2011-08-14 07:27:51.582233000 +0530
+++ dst/gdb/NEWS	2011-08-14 07:50:38.562234498 +0530
@@ -64,6 +64,9 @@
 
 * New commands "info macros", and "info definitions" have been added.
 
+* New command "pipe" has been added to make GDB command output available to the
+  shell for processing. 
+
 * Changed commands
 
 watch EXPRESSION mask MASK_VALUE
diff -rup src/gdb/pipe.c dst/gdb/pipe.c
--- src/gdb/pipe.c	2011-07-29 15:15:26.078048517 +0530
+++ dst/gdb/pipe.c	2011-08-16 14:05:56.771665999 +0530
@@ -0,0 +1,227 @@
+/* Everything about pipe, for GDB.
+
+   Copyright (C) 2011 Free Software Foundation, Inc.
+
+   This file is part of GDB.
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program 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 General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
+
+#include "defs.h"
+#include <ctype.h>
+#include "gdb_string.h"
+#include "ui-file.h"
+#include "ui-out.h"
+#include "cli/cli-utils.h"
+#include "gdbcmd.h"
+#include "libiberty.h"
+#include "exceptions.h"
+
+#if defined(__MINGW32__)
+#define SHELL "cmd.exe"
+#define OPTION_TO_SHELL "/c"
+#else
+#define SHELL "/bin/sh"
+#define OPTION_TO_SHELL "-c"
+#endif
+
+/* Structure to encapsulate all entities associated with pipe.  */
+
+struct pipe_obj
+{
+  /* The delimiter to separate out gdb-command and shell-command.  This can be
+     any arbitrary string without containing any whitespace.  */
+  char *dlim;
+
+  /* The gdb-command.  */
+  char *gdb_cmd;
+
+  /* The shell-command.  */
+  char *shell_cmd;
+
+  /* The gdb-side stream pointer to the pipe.  */
+  FILE *handle;
+
+  /* The pex object used to create pipeline between gdb and shell.  */
+  struct pex_obj *pex;
+};
+
+/* Destruct pipe object referenced by ARG.  */
+
+static void
+destruct_pipe (void *arg)
+{
+  struct pipe_obj *pipe = (struct pipe_obj *) arg;
+
+  if (pipe->handle != NULL)
+    fclose (pipe->handle);
+
+  if (pipe->pex != NULL)
+    {
+      int status;
+
+      /* Wait till the process on the other side of the pipe completes its
+	 job before closing its file descriptors.  */
+      pex_get_status (pipe->pex, 1, &status);
+
+      if (!WIFEXITED (status))
+	warning (_("Execution of shell-command `%s' may not be completed"),
+		 pipe->shell_cmd);
+
+      pex_free (pipe->pex);
+    }
+
+  xfree (pipe->dlim);
+  xfree (pipe);
+}
+
+/* Construct a pipe object by parsing argument ARG to the pipe command.  */
+
+static struct pipe_obj *
+construct_pipe (char *arg)
+{
+  char *p, *t;
+  struct pipe_obj *pipe = NULL;
+  struct cleanup *cleanup;
+
+  if (arg == NULL)
+    error (_("No argument is specified"));
+
+  pipe = XCNEW (struct pipe_obj);
+  cleanup = make_cleanup (destruct_pipe, pipe);
+
+  p = xstrdup (arg);
+  pipe->dlim = p;
+
+  if (*pipe->dlim == '-')
+    error (_("Delimiter pattern should not start with '-'"));
+
+  t = skip_to_space (p);
+  p = skip_spaces (t);
+
+  if (*p == '\0')
+    error (_("No gdb-command is specified"));
+
+  *t = '\0';
+  pipe->gdb_cmd = p;
+
+  for (;;)
+    {
+      t = skip_to_space (p);
+
+      if (*t == '\0')
+	error (_("No shell-command is specified"));
+
+      /* Check whether the token separated by whitespace matches with
+	 delimiter.  */ 
+      if (memcmp (p, pipe->dlim, (t - p)) == 0
+	  && pipe->dlim[t - p] == '\0')
+	{
+	  *p = '\0';
+	  pipe->shell_cmd = skip_spaces (t);
+	  break;
+	}
+
+       p = skip_spaces (t);
+    }
+
+  discard_cleanups (cleanup);
+  return pipe;
+}
+
+/* Run execute_command for PIPE and FROM_TTY.  Write output to the pipe, do not
+   display it to the screen.  */
+
+static void
+execute_command_to_pipe (struct pipe_obj *pipe, int from_tty)
+{
+  char *argv[4];
+  struct cleanup *cleanup;
+  struct ui_file *fp;
+  int status;
+  const char *errmsg;
+  volatile struct gdb_exception exception;
+
+  argv[0] = SHELL;
+  argv[1] = OPTION_TO_SHELL;
+  argv[2] = pipe->shell_cmd;
+  argv[3] = NULL;
+
+  pipe->pex = pex_init (PEX_USE_PIPES, argv[0], NULL);
+  pipe->handle = pex_input_pipe (pipe->pex, 0);
+
+  if (pipe->handle == NULL)
+    error (_("Failed to create pipe"));
+
+  errmsg = pex_run (pipe->pex, PEX_LAST, argv[0], argv, NULL, NULL, &status);
+
+  if (errmsg != NULL)
+    error (_("Failed to execute shell-command `%s' on pipe: %s"),
+	   pipe->shell_cmd, errmsg);
+
+  /* GDB_STDOUT should be better already restored during these
+     restoration callbacks.  */
+  cleanup = set_batch_flag_and_make_cleanup_restore_page_info ();
+  fp = stdio_fileopen (pipe->handle);
+  make_cleanup_ui_file_delete (fp);
+  make_cleanup_restore_ui_file (&gdb_stdout);
+  make_cleanup_restore_ui_file (&gdb_stderr);
+  make_cleanup_restore_ui_file (&gdb_stdlog);
+  make_cleanup_restore_ui_file (&gdb_stdtarg);
+  make_cleanup_restore_ui_file (&gdb_stdtargerr);
+
+  if (ui_out_redirect (current_uiout, fp) < 0)
+    warning (_("Current output protocol does not support redirection"));
+  else 
+    make_cleanup_ui_out_redirect_pop (current_uiout);
+
+  gdb_stdout = fp;
+  gdb_stderr = fp;
+  gdb_stdlog = fp;
+  gdb_stdtarg = fp;
+  gdb_stdtargerr = fp;
+
+  TRY_CATCH (exception, RETURN_MASK_ERROR)
+    {
+      execute_command (pipe->gdb_cmd, from_tty);
+    }
+
+  if (exception.reason < 0)
+    exception_print (gdb_stderr, exception);
+
+  do_cleanups (cleanup);
+}
+
+/* Execute the pipe command with argument ARG and FROM_TTY.  */
+
+static void
+pipe_command (char *arg, int from_tty)
+{
+  struct pipe_obj *pipe = construct_pipe (arg);
+  struct cleanup *cleanup = make_cleanup (destruct_pipe, pipe);
+
+  execute_command_to_pipe (pipe, from_tty);
+  do_cleanups (cleanup);
+}
+
+/* Module initialization.  */
+
+void
+_initialize_pipe (void)
+{
+  add_cmd ("pipe", no_class, pipe_command, _("\
+Create pipe to pass gdb-command output to the shell for processing.\n\
+Arguments are a delimiter, followed by a gdb-command, then the same delimiter \
+again and finally a shell-command."),
+	   &cmdlist);
+}

Attachment: ChangeLog
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