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

[Jan Kratochvil <jan dot kratochvil at redhat dot com>]

On Tue, 16 Aug 2011 14:45:19 +0200, Abhijit Halder wrote:
> +#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

GNU Coding style would say:
#if defined (__MINGW32__)
but #ifdef would be also OK IMO.

and indent, please:

# define SHELL "cmd.exe"
# define OPTION_TO_SHELL "/c"
#else
# define SHELL "/bin/sh"
# define OPTION_TO_SHELL "-c"
#endif

It would be nice to get the __MINGW32__ tested but OK to check it in if no
test appears, some __MINGW32__ fix later may be easy.


> +
> +/* 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);

WEXITSTATUS could be checked but you may not agree, OK if so.


> +
> +      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)

ARG can be now `const char *' when it is xstrdup-ed anyway.

> +{
> +  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);

Also output: safe_strerror (status)


> +
> +  /* 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);
> +}


But otherwise OK to check it in with those few changes, approved doc and the
testcase.


Thanks,
Jan