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

Abhijit Halder
2011-08-16T12:45:45Z

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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.

[-- Attachment #2: gdb-pipe-command-corrected.patch --]
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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 #3: ChangeLog --]
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2011-07-29 Abhijit Halder <abhijit.k.halder@gmail.com>

Implementation of pipe to make I/O communication
between gdb and shell.

* pipe.c: New file.
* Makefile.in (SFILES): Add pipe.c.
(COMMON_OBS): Add pipe.o.
* NEWS: Add news item for the new command `pipe'.