Remove pipe mode of operation

This was extra complexity, and created a problem; see
#67

In short, librecode forking could cause output from the calling process to
be duplicated, as stdio buffers would be flushed when a child process ended,
and then flushed again later in the (duplicate) copy in the caller. This is
hard to get around nicely.

Since there’s little evidence that the multi-process operation was bringing
significant benefits, and since a duplicate bug that had not been fixed on
the non-pipe code path was recently spotted as well, remove the pipe code
path.

Author: rrthomas

bootstrap.conf

@@ -1,4 +1,4 @@
-# bootstrap.conf (Recode) version 2023-02-11
+# bootstrap.conf (Recode) version 2025-03-25
 
 # This file is part of Recode.
 #
@@ -65,7 +65,6 @@ gnulib_modules='
         minmax
         mkstemps
         pathmax
-        pipe-posix
         quotearg
         sigaction
         strndup

doc/recode.texi

@@ -123,7 +123,6 @@ How to use this program
 * Listings::            Asking for various lists
 * Recoding::            Controlling how files are recoded
 * Reversibility::       Reversibility issues
-* Sequencing::          Selecting sequencing methods
 * Mixed::               Using mixed charset input
 * Emacs::               Using Recode within Emacs
 * Debugging::           Debugging considerations
@@ -548,7 +547,6 @@ control.
 * Listings::            Asking for various lists
 * Recoding::            Controlling how files are recoded
 * Reversibility::       Reversibility issues
-* Sequencing::          Selecting sequencing methods
 * Mixed::               Using mixed charset input
 * Emacs::               Using Recode within Emacs
 * Debugging::           Debugging considerations
@@ -1209,7 +1207,7 @@ requests offers a finer control, @pxref{Requests}).
 @var{charset} may be abbreviated to any unambiguous prefix.
 @end table
 
-@node Reversibility, Sequencing, Recoding, Invoking recode
+@node Reversibility, Mixed, Recoding, Invoking recode
 @section Reversibility issues
 
 The following options are somewhat related to reversibility issues:
@@ -1411,56 +1409,7 @@ length 3.  On the other end, recoding six times in the same direction
 would recover all characters in cycles of length 1, 2, 3 or 6.
 @end enumerate
 
-@node Sequencing, Mixed, Reversibility, Invoking recode
-@section Selecting sequencing methods
-
-@cindex sequencing
-Recode can split itself into multiple parallel processes when it is
-discovered that many passes are needed to comply with the @var{request}.
-For example, suppose that four elementary steps were selected at
-recoding path optimisation time.  Then Recode will split itself into
-four different interconnected tasks, logically equivalent to:
-
-@example
-@var{step1} <@var{input} | @var{step2} | @var{step3} | @var{step4} >@var{output}
-@end example
-
-On systems where the pipes method is not available, the steps are
-performed in series.
-
-@table @samp
-@item --sequence=memory
-@opindex --sequence
-@cindex memory sequencing
-When the recoding requires a combination of two or more elementary
-recoding steps, this option forces many passes over the data, using
-in-memory buffers to hold all intermediate results.
-If this option is selected in filter
-mode, that is, when the program reads standard input and writes standard
-output, it might take longer for programs further down the pipe chain to
-start receiving some recoded data.
-
-@item -p
-@itemx --sequence=pipe
-@opindex -p
-@cindex pipe sequencing
-When the recoding requires a combination of two or more elementary
-recoding steps, this option forces the program to fork itself into a few
-copies interconnected with pipes, using the @code{pipe(2)} system call.
-All copies of the program operate in parallel.  This is the default
-behaviour in filter mode.  If this option is used when files are recoded
-over themselves, this should also save disk space because some temporary
-files might not be needed, at the cost of more system overhead.
-
-@item -i
-@itemx --sequence=files
-@opindex -i
-@cindex file sequencing
-This option is accepted for backwards compatibility, and acts like
-@samp{--sequence=memory}.
-@end table
-
-@node Mixed, Emacs, Sequencing, Invoking recode
+@node Mixed, Emacs, Reversibility, Invoking recode
 @section Using mixed charset input
 
 In real life and practice, textual files are often made up of many charsets

lib/.gitignore

@@ -82,7 +82,6 @@
 /msvc-nothrow.c
 /msvc-nothrow.h
 /pathmax.h
-/pipe.c
 /printf-args.c
 /printf-args.h
 /printf-frexp.c

m4/.gitignore

@@ -52,7 +52,6 @@ gnulib-comp.m4
 /nocrash.m4
 /off_t.m4
 /pathmax.m4
-/pipe.m4
 /printf-frexp.m4
 /printf-frexpl.m4
 /printf.m4

src/main.c

@@ -133,35 +133,6 @@ task_perror (RECODE_CONST_TASK task)
       return _("Internal recoding bug");
     }
 }
-
-/*-----------------.
-| Signal handler.  |
-`-----------------*/
-
-#ifdef HAVE_PIPE
-static void
-sig_catch(int sig, void (*handler) (int))
-{
-  struct sigaction sa;
-  sa.sa_handler = handler;
-  sa.sa_flags = 0;
-  sigemptyset (&sa.sa_mask);
-  sigaction (sig, &sa, NULL);  /* ignore error: none possible */
-}
-
-static void
-signal_handler (int number)
-{
-  recode_interrupted = 1;
-  sig_catch (number, signal_handler);
-}
-
-static void
-setup_signals (void)
-{
- sig_catch (SIGPIPE, signal_handler);
-}
-#endif
 
 /* Main control.  */
 
@@ -777,10 +748,6 @@ warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.\n"),
   /* Discard the request argument.  */
   optind++;
 
-#if HAVE_PIPE
-  setup_signals ();
-#endif
-
   {
     RECODE_TASK task;
 

src/task.c

@@ -232,11 +232,6 @@ recode_perform_task (RECODE_TASK task)
   struct recode_subtask subtask_block;
   RECODE_SUBTASK subtask = &subtask_block;
 
-#if HAVE_PIPE
-  int pipe_pair[2];		/* pair of file descriptors for a pipe */
-  pid_t wait_status;		/* status returned by wait() */
-#endif
-
   struct recode_read_write_text input;
   struct recode_read_write_text output;
   memset (&input, 0, sizeof (struct recode_read_write_text));
@@ -298,71 +293,6 @@ recode_perform_task (RECODE_TASK task)
 	{
           subtask->output = output;
           subtask->output.cursor = subtask->output.buffer;
-
-#if HAVE_PIPE
-          /* Create all subprocesses, from the first to the last, and
-             interconnect them.  */
-
-          if (pipe (pipe_pair) < 0)
-            {
-              recode_perror (NULL, "pipe ()");
-              recode_if_nogo (RECODE_SYSTEM_ERROR, subtask);
-              SUBTASK_RETURN (subtask);
-            }
-          xset_binary_mode (pipe_pair[0], O_BINARY);
-          xset_binary_mode (pipe_pair[1], O_BINARY);
-          if (child_process = fork (), child_process < 0)
-            {
-              recode_perror (NULL, "fork ()");
-              recode_if_nogo (RECODE_SYSTEM_ERROR, subtask);
-              SUBTASK_RETURN (subtask);
-            }
-          if (child_process == 0)
-            {
-              /* The child executes its recoding step, reading from the
-                 current input file and writing to the pipe; then it exits.  */
-
-              if (close (pipe_pair[0]) < 0)
-                {
-                  recode_perror (NULL, "close ()");
-                  recode_if_nogo (RECODE_SYSTEM_ERROR, subtask);
-                }
-              if (subtask->output.file = fdopen (pipe_pair[1], "w"),
-                  subtask->output.file == NULL)
-                {
-                  recode_perror (NULL, "fdopen ()");
-                  recode_if_nogo (RECODE_SYSTEM_ERROR, subtask);
-                }
-            }
-          else
-            {
-              /* The parent saves the read end of the pipe for the next step.  */
-
-              if (input.file = fdopen (pipe_pair[0], "r"),
-                  input.file == NULL)
-                {
-                  recode_perror (NULL, "fdopen ()");
-                  recode_if_nogo (RECODE_SYSTEM_ERROR, subtask);
-                  close (pipe_pair[0]);
-                  close (pipe_pair[1]);
-                  SUBTASK_RETURN (subtask);
-                }
-              if (close (pipe_pair[1]) < 0)
-                {
-                  recode_perror (NULL, "close ()");
-                  recode_if_nogo (RECODE_SYSTEM_ERROR, subtask);
-                  close (pipe_pair[0]);
-                  fclose (input.file);
-                  SUBTASK_RETURN (subtask);
-                }
-
-              /* Close the input file when we opened it. */
-
-              if (subtask->input.file && subtask->input.name &&
-                  subtask->input.name[0])
-                fclose (subtask->input.file);
-            }
-#endif
 	}
       else
 	{
@@ -395,9 +325,6 @@ recode_perform_task (RECODE_TASK task)
 	  subtask->step = request->sequence_array + sequence_index;
 	  (*subtask->step->transform_routine) (subtask);
 
-#if HAVE_PIPE
-          break;	/* child/top-level process: escape from loop */
-#else
 	  /* Post-step clean up for memory sequence.  */
 
 	  if (subtask->input.file)
@@ -422,7 +349,6 @@ recode_perform_task (RECODE_TASK task)
 	      output = input;
 	      input = subtask->output;
 	    }
-#endif
 	}
 
       if (sequence_index + 1 == (unsigned)request->sequence_length)
@@ -444,57 +370,8 @@ recode_perform_task (RECODE_TASK task)
       recode_if_nogo (RECODE_SYSTEM_ERROR, subtask);
     }
 
-#if HAVE_PIPE
-  /* Child process exits here. */
-
-  if (child_process == 0)
-    exit (task->error_so_far < task->fail_level ? EXIT_SUCCESS
-          : EXIT_FAILURE);
-  else
-    {
-      /* Wait on all children, mainly to avoid synchronisation problems on
-         output file contents, but also to reduce the number of zombie
-         processes in case the user recodes many files at once.  */
-
-      while (wait (&wait_status) > 0)
-        {
-          /* Diagnose and abort on any abnormally terminating child.  */
-
-          if (!(WIFEXITED (wait_status)
-                || (WIFSIGNALED (wait_status)
-                    && WTERMSIG (wait_status) == SIGPIPE)))
-            {
-              recode_error (NULL, _("Child process wait status is 0x%0.2x"),
-                            wait_status);
-              recode_if_nogo (RECODE_SYSTEM_ERROR, subtask);
-              SUBTASK_RETURN (subtask);
-            }
-
-          /* Check for a nonzero exit from the terminating child.  */
-
-          if (WIFEXITED (wait_status)
-              ? WEXITSTATUS (wait_status) != 0
-              : WTERMSIG (wait_status) != 0)
-            /* FIXME: It is not very clear what happened in sub-processes.  */
-            if (task->error_so_far < task->fail_level)
-              {
-                task->error_so_far = task->fail_level;
-                task->error_at_step = request->sequence_array + (unsigned)request->sequence_length - 1;
-              }
-        }
-
-      if (recode_interrupted)
-        /* FIXME: It is not very clear what happened in sub-processes.  */
-        if (task->error_so_far < task->fail_level)
-          {
-            task->error_so_far = task->fail_level;
-            task->error_at_step = request->sequence_array + (unsigned)request->sequence_length - 1;
-          }
-    }
-#else
   free (input.buffer);
   free (output.buffer);
-#endif
 
   task->output = subtask->output;
   SUBTASK_RETURN (subtask);