merge from gcc

11 files changed, 388 insertions, 52 deletions

diff --git a/include/ChangeLog b/include/ChangeLog
index af4eb6d758..0a3787aac3 100644
--- a/include/ChangeLog
+++ b/include/ChangeLog
@@ -1,3 +1,7 @@
+2006-04-11  Jim Blandy  <jimb@codesourcery.com>
+
+	* libiberty.h (pex_input_file, pex_input_pipe): New declarations.
+
 2006-04-06  H.J. Lu  <hongjiu.lu@intel.com>
 
 	* bfdlink.h (bfd_link_info): Replace need_relax_finalize with
diff --git a/include/libiberty.h b/include/libiberty.h
index c264cb2ab0..6bd318e0fe 100644
--- a/include/libiberty.h
+++ b/include/libiberty.h
@@ -448,6 +448,47 @@ extern const char *pex_run (struct pex_obj *obj, int flags,
 			    const char *outname, const char *errname,
 			    int *err);
 
+/* Return a `FILE' pointer FP for the standard input of the first
+   program in the pipeline; FP is opened for writing.  You must have
+   passed `PEX_USE_PIPES' to the `pex_init' call that returned OBJ.
+   You must close FP yourself with `fclose' to indicate that the
+   pipeline's input is complete.
+
+   The file descriptor underlying FP is marked not to be inherited by
+   child processes.
+
+   This call is not supported on systems which do not support pipes;
+   it returns with an error.  (We could implement it by writing a
+   temporary file, but then you would need to write all your data and
+   close FP before your first call to `pex_run' -- and that wouldn't
+   work on systems that do support pipes: the pipe would fill up, and
+   you would block.  So there isn't any easy way to conceal the
+   differences between the two types of systems.)
+
+   If you call both `pex_write_input' and `pex_read_output', be
+   careful to avoid deadlock.  If the output pipe fills up, so that
+   each program in the pipeline is waiting for the next to read more
+   data, and you fill the input pipe by writing more data to FP, then
+   there is no way to make progress: the only process that could read
+   data from the output pipe is you, but you are blocked on the input
+   pipe.  */
+
+extern FILE *pex_write_input (struct pex_obj *obj, int binary);
+
+/* Return a stream for a temporary file to pass to the first program
+   in the pipeline as input.  The file name is chosen as for pex_run.
+   pex_run closes the file automatically; don't close it yourself.  */
+
+extern FILE *pex_input_file (struct pex_obj *obj, int flags,
+                             const char *in_name);
+
+/* Return a stream for a pipe connected to the standard input of the
+   first program in the pipeline.  You must have passed
+   `PEX_USE_PIPES' to `pex_init'.  Close the returned stream
+   yourself.  */
+
+extern FILE *pex_input_pipe (struct pex_obj *obj, int binary);
+
 /* Read the standard output of the last program to be executed.
    pex_run can not be called after this.  BINARY should be non-zero if
    the file should be opened in binary mode; this is ignored on Unix.
diff --git a/libiberty/ChangeLog b/libiberty/ChangeLog
index e79c27f7da..fb328da633 100644
--- a/libiberty/ChangeLog
+++ b/libiberty/ChangeLog
@@ -1,3 +1,25 @@
+2006-03-29  Jim Blandy  <jimb@codesourcery.com>
+
+ 	* pex-common.c (pex_input_file, pex_input_pipe): New functions.
+	(pex_init_common): Initialize obj->input_file.
+	(pex_run): Close any file opened by pex_input_file.
+ 	* pexecute.txh (pex_input_file, pex_input_pipe): New docs.
+ 	* pex-common.h (struct pex_obj): New field input_file.
+	(struct pex_funcs): New function ptr fdopenw.
+ 	* pex-unix.c (pex_unix_fdopenw): New function.
+ 	(funcs): List it as our fdopenw function.
+ 	* pex-win32.c (pex_win32_fdopenw): New function.
+ 	(funcs): List it as our fdopenw function.
+ 	* pex-djgpp.c (funcs): Leave fdopenw null.
+ 	* pex-msdos (funcs): Same.
+ 	* functions.texi: Regenerated.
+
+2006-04-10  Jim Blandy  <jimb@codesourcery.com>
+
+	* pex-common.c (temp_file): New function, containing guts of
+	pex-style temporary file name generation.
+	(pex_run): Use it.
+
 2006-04-06  Carlos O'Donell  <carlos@codesourcery.com>
 
 	* Makefile.in: Add install-html, install-html-am, and
diff --git a/libiberty/functions.texi b/libiberty/functions.texi
index a09e2075fe..fa92d702d7 100644
--- a/libiberty/functions.texi
+++ b/libiberty/functions.texi
@@ -668,14 +668,14 @@ reading and writing.
 
 @end deftypefn
 
-@c pexecute.txh:169
+@c pexecute.txh:231
 @deftypefn Extension void pex_free (struct pex_obj @var{obj})
 
 Clean up and free all data associated with @var{obj}.
 
 @end deftypefn
 
-@c pexecute.txh:144
+@c pexecute.txh:206
 @deftypefn Extension int pex_get_status (struct pex_obj *@var{obj}, int @var{count}, int *@var{vector})
 
 Returns the exit status of all programs run using @var{obj}.
@@ -685,7 +685,7 @@ to @code{pex_run}.  Returns 0 on error, 1 on success.
 
 @end deftypefn
 
-@c pexecute.txh:153
+@c pexecute.txh:215
 @deftypefn Extension int pex_get_times (struct pex_obj *@var{obj}, int @var{count}, struct pex_time *@var{vector})
 
 Returns the process execution times of all programs run using
@@ -702,7 +702,7 @@ process times, all the fields will be set to @code{0}.
 
 @end deftypefn
 
-@c pexecute.txh:1
+@c pexecute.txh:2
 @deftypefn Extension {struct pex_obj *} pex_init (int @var{flags}, const char *@var{pname}, const char *@var{tempbase})
 
 Prepare to execute one or more programs, with standard output of each
@@ -734,7 +734,70 @@ temporary files; it may be @code{NULL} to use a randomly chosen name.
 
 @end deftypefn
 
-@c pexecute.txh:175
+@c pexecute.txh:133
+@deftypefn Extension {FILE *} pex_input_file (struct pex_obj *@var{obj}, int @var{flags}, const char *@var{in_name})
+
+Return a stream for a temporary file to pass to the first program in
+the pipeline as input.
+
+The name of the input file is chosen according to the same rules
+@code{pex_run} uses to choose output file names, based on
+@var{in_name}, @var{obj} and the @code{PEX_SUFFIX} bit in @var{flags}.
+
+Don't call @code{fclose} on the returned stream; the first call to
+@code{pex_run} closes it automatically.
+
+If @var{flags} includes @code{PEX_BINARY_OUTPUT}, open the stream in
+binary mode; otherwise, open it in the default mode.  Including
+@code{PEX_BINARY_OUTPUT} in @var{flags} has no effect on Unix.
+@end deftypefn
+
+@c pexecute.txh:150
+@deftypefn Extension {FILE *} pex_input_pipe (struct pex_obj *@var{obj}, int @var{binary})
+
+Return a stream @var{fp} for a pipe connected to the standard input of
+the first program in the pipeline; @var{fp} is opened for writing.
+You must have passed @code{PEX_USE_PIPES} to the @code{pex_init} call
+that returned @var{obj}.
+
+You must close @var{fp} using @code{fclose} yourself when you have
+finished writing data to the pipeline.
+
+The file descriptor underlying @var{fp} is marked not to be inherited
+by child processes.
+
+On systems that do not support pipes, this function returns
+@code{NULL}, and sets @code{errno} to @code{EINVAL}.  If you would
+like to write code that is portable to all systems the @code{pex}
+functions support, consider using @code{pex_input_file} instead.
+
+There are two opportunities for deadlock using
+@code{pex_input_pipe}:
+
+@itemize @bullet
+@item
+Most systems' pipes can buffer only a fixed amount of data; a process
+that writes to a full pipe blocks.  Thus, if you write to @file{fp}
+before starting the first process, you run the risk of blocking when
+there is no child process yet to read the data and allow you to
+continue.  @code{pex_input_pipe} makes no promises about the
+size of the pipe's buffer, so if you need to write any data at all
+before starting the first process in the pipeline, consider using
+@code{pex_input_file} instead.
+
+@item
+Using @code{pex_input_pipe} and @code{pex_read_output} together
+may also cause deadlock.  If the output pipe fills up, so that each
+program in the pipeline is waiting for the next to read more data, and
+you fill the input pipe by writing more data to @var{fp}, then there
+is no way to make progress: the only process that could read data from
+the output pipe is you, but you are blocked on the input pipe.
+
+@end itemize
+
+@end deftypefn
+
+@c pexecute.txh:237
 @deftypefn Extension {const char *} pex_one (int @var{flags}, const char *@var{executable}, char * const *@var{argv}, const char *@var{pname}, const char *@var{outname}, const char *@var{errname}, int *@var{status}, int *@var{err})
 
 An interface to permit the easy execution of a
@@ -747,7 +810,7 @@ be set to the exit status of the program.
 
 @end deftypefn
 
-@c pexecute.txh:132
+@c pexecute.txh:194
 @deftypefn Extension {FILE *} pex_read_output (struct pex_obj *@var{obj}, int @var{binary})
 
 Returns a @code{FILE} pointer which may be used to read the standard
@@ -760,7 +823,7 @@ it will be closed by @code{pex_free}.
 
 @end deftypefn
 
-@c pexecute.txh:32
+@c pexecute.txh:33
 @deftypefn Extension {const char *} pex_run (struct pex_obj *@var{obj}, int @var{flags}, const char *@var{executable}, char * const *@var{argv}, const char *@var{outname}, const char *@var{errname}, int *@var{err})
 
 Execute one program in a pipeline.  On success this returns
@@ -861,7 +924,7 @@ value, or to 0 if there is no relevant @code{errno}.
 
 @end deftypefn
 
-@c pexecute.txh:187
+@c pexecute.txh:249
 @deftypefn Extension int pexecute (const char *@var{program}, char * const *@var{argv}, const char *@var{this_pname}, const char *@var{temp_base}, char **@var{errmsg_fmt}, char **@var{errmsg_arg}, int flags)
 
 This is the old interface to execute one or more programs.  It is
@@ -889,7 +952,7 @@ name is unset/removed.
 
 @end deftypefn
 
-@c pexecute.txh:195
+@c pexecute.txh:257
 @deftypefn Extension int pwait (int @var{pid}, int *@var{status}, int @var{flags})
 
 Another part of the old execution interface.
diff --git a/libiberty/pex-common.c b/libiberty/pex-common.c
index db842aed24..ebe8c43759 100644
--- a/libiberty/pex-common.c
+++ b/libiberty/pex-common.c
@@ -67,6 +67,7 @@ pex_init_common (int flags, const char *pname, const char *tempbase,
   obj->status = NULL;
   obj->time = NULL;
   obj->number_waited = 0;
+  obj->input_file = NULL;
   obj->read_output = NULL;
   obj->remove_count = 0;
   obj->remove = NULL;
@@ -91,6 +92,56 @@ pex_add_remove (struct pex_obj *obj, const char *name, int allocated)
   obj->remove[obj->remove_count - 1] = add;
 }
 
+/* Generate a temporary file name based on OBJ, FLAGS, and NAME.
+   Return NULL if we were unable to reserve a temporary filename.
+
+   If non-NULL, the result is either allocated with malloc, or the
+   same pointer as NAME.  */
+static char *
+temp_file (struct pex_obj *obj, int flags, char *name)
+{
+  if (name == NULL)
+    {
+      if (obj->tempbase == NULL)
+        {
+          name = make_temp_file (NULL);
+        }
+      else
+        {
+          int len = strlen (obj->tempbase);
+          int out;
+
+          if (len >= 6
+              && strcmp (obj->tempbase + len - 6, "XXXXXX") == 0)
+            name = xstrdup (obj->tempbase);
+          else
+            name = concat (obj->tempbase, "XXXXXX", NULL);
+
+          out = mkstemps (name, 0);
+          if (out < 0)
+            {
+              free (name);
+              return NULL;
+            }
+
+          /* This isn't obj->funcs->close because we got the
+             descriptor from mkstemps, not from a function in
+             obj->funcs.  Calling close here is just like what
+             make_temp_file does.  */
+          close (out);
+        }
+    }
+  else if ((flags & PEX_SUFFIX) != 0)
+    {
+      if (obj->tempbase == NULL)
+        name = make_temp_file (name);
+      else
+        name = concat (obj->tempbase, name, NULL);
+    }
+
+  return name;
+}
+
 /* Run a program.  */
 
 const char *
@@ -111,6 +162,17 @@ pex_run (struct pex_obj *obj, int flags, const char *executable,
   outname = (char *) orig_outname;
   outname_allocated = 0;
 
+  /* If the user called pex_input_file, close the file now.  */
+  if (obj->input_file)
+    {
+      if (fclose (obj->input_file) == EOF)
+        {
+          errmsg = "closing pipeline input file";
+          goto error_exit;
+        }
+      obj->input_file = NULL;
+    }
+
   /* Set IN.  */
 
   if (obj->next_input_name != NULL)
@@ -161,49 +223,16 @@ pex_run (struct pex_obj *obj, int flags, const char *executable,
     }
   else if ((obj->flags & PEX_USE_PIPES) == 0)
     {
-      if (outname == NULL)
-	{
-	  if (obj->tempbase == NULL)
-	    {
-	      outname = make_temp_file (NULL);
-	      outname_allocated = 1;
-	    }
-	  else
-	    {
-	      int len = strlen (obj->tempbase);
-
-	      if (len >= 6
-		  && strcmp (obj->tempbase + len - 6, "XXXXXX") == 0)
-		outname = xstrdup (obj->tempbase);
-	      else
-		outname = concat (obj->tempbase, "XXXXXX", NULL);
-
-	      outname_allocated = 1;
-
-	      out = mkstemps (outname, 0);
-	      if (out < 0)
-		{
-		  *err = 0;
-		  errmsg = "could not create temporary output file";
-		  goto error_exit;
-		}
-
-	      /* This isn't obj->funcs->close because we got the
-		 descriptor from mkstemps, not from a function in
-		 obj->funcs.  Calling close here is just like what
-		 make_temp_file does.  */
-	      close (out);
-	      out = -1;
-	    }
-	}
-      else if ((flags & PEX_SUFFIX) != 0)
-	{
-	  if (obj->tempbase == NULL)
-	    outname = make_temp_file (outname);
-	  else
-	    outname = concat (obj->tempbase, outname, NULL);
-	  outname_allocated = 1;
-	}
+      outname = temp_file (obj, flags, outname);
+      if (! outname)
+        {
+          *err = 0;
+          errmsg = "could not create temporary file";
+          goto error_exit;
+        }
+
+      if (outname != orig_outname)
+        outname_allocated = 1;
 
       if ((obj->flags & PEX_SAVE_TEMPS) == 0)
 	{
@@ -290,6 +319,87 @@ pex_run (struct pex_obj *obj, int flags, const char *executable,
   return errmsg;
 }
 
+/* Return a FILE pointer for a temporary file to fill with input for
+   the pipeline.  */
+FILE *
+pex_input_file (struct pex_obj *obj, int flags, const char *in_name)
+{
+  char *name = (char *) in_name;
+  FILE *f;
+
+  /* This must be called before the first pipeline stage is run, and
+     there must not have been any other input selected.  */
+  if (obj->count != 0
+      || (obj->next_input >= 0 && obj->next_input != STDIN_FILE_NO)
+      || obj->next_input_name)
+    {
+      errno = EINVAL;
+      return NULL;
+    }
+
+  name = temp_file (obj, flags, name);
+  if (! name)
+    return NULL;
+
+  f = fopen (name, (flags & PEX_BINARY_OUTPUT) ? "wb" : "w");
+  if (! f)
+    {
+      free (name);
+      return NULL;
+    }
+
+  obj->input_file = f;
+  obj->next_input_name = name;
+  obj->next_input_name_allocated = (name != in_name);
+
+  return f;
+}
+
+/* Return a stream for a pipe connected to the standard input of the
+   first stage of the pipeline.  */
+FILE *
+pex_input_pipe (struct pex_obj *obj, int binary)
+{
+  int p[2];
+  FILE *f;
+
+  /* You must call pex_input_pipe before the first pex_run or pex_one.  */
+  if (obj->count > 0)
+    goto usage_error;
+
+  /* You must be using pipes.  Implementations that don't support
+     pipes clear this flag before calling pex_init_common.  */
+  if (! (obj->flags & PEX_USE_PIPES))
+    goto usage_error;
+
+  /* If we have somehow already selected other input, that's a
+     mistake.  */
+  if ((obj->next_input >= 0 && obj->next_input != STDIN_FILE_NO)
+      || obj->next_input_name)
+    goto usage_error;
+
+  if (obj->funcs->pipe (obj, p, binary != 0) < 0)
+    return NULL;
+
+  f = obj->funcs->fdopenw (obj, p[WRITE_PORT], binary != 0);
+  if (! f)
+    {
+      int saved_errno = errno;
+      obj->funcs->close (obj, p[READ_PORT]);
+      obj->funcs->close (obj, p[WRITE_PORT]);
+      errno = saved_errno;
+      return NULL;
+    }
+
+  obj->next_input = p[READ_PORT];
+
+  return f;
+
+ usage_error:
+  errno = EINVAL;
+  return NULL;
+}
+
 /* Return a FILE pointer for the output of the last program
    executed.  */
 
diff --git a/libiberty/pex-common.h b/libiberty/pex-common.h
index b70b38d973..8ded138148 100644
--- a/libiberty/pex-common.h
+++ b/libiberty/pex-common.h
@@ -69,6 +69,8 @@ struct pex_obj
   struct pex_time *time;
   /* Number of children we have already waited for.  */
   int number_waited;
+  /* FILE created by pex_input_file.  */
+  FILE *input_file;
   /* FILE created by pex_read_output.  */
   FILE *read_output;
   /* Number of temporary files to remove.  */
@@ -121,6 +123,11 @@ struct pex_funcs
      PEX_USE_PIPES is set).  If BINARY is non-zero, open in binary
      mode.  Return pointer on success, NULL on error.  */
   FILE * (*fdopenr) (struct pex_obj *, int /* fd */, int /* binary */);
+  /* Get a FILE pointer to write to the file descriptor FD (only
+     called if PEX_USE_PIPES is set).  If BINARY is non-zero, open in
+     binary mode.  Arrange for FD not to be inherited by the child
+     processes.  Return pointer on success, NULL on error.  */
+  FILE * (*fdopenw) (struct pex_obj *, int /* fd */, int /* binary */);
   /* Free any system dependent data associated with OBJ.  May be
      NULL if there is nothing to do.  */
   void (*cleanup) (struct pex_obj *);
diff --git a/libiberty/pex-djgpp.c b/libiberty/pex-djgpp.c
index 6e58e3fd8d..17fbf2cc7e 100644
--- a/libiberty/pex-djgpp.c
+++ b/libiberty/pex-djgpp.c
@@ -62,6 +62,7 @@ const struct pex_funcs funcs =
   pex_djgpp_wait,
   NULL, /* pipe */
   NULL, /* fdopenr */
+  NULL, /* fdopenw */
   NULL  /* cleanup */
 };
 
diff --git a/libiberty/pex-msdos.c b/libiberty/pex-msdos.c
index 2256117d1b..db22337aa2 100644
--- a/libiberty/pex-msdos.c
+++ b/libiberty/pex-msdos.c
@@ -73,6 +73,7 @@ const struct pex_funcs funcs =
   pex_msdos_wait,
   NULL, /* pipe */
   NULL, /* fdopenr */
+  NULL, /* fdopenw */
   pex_msdos_cleanup
 };
 
diff --git a/libiberty/pex-unix.c b/libiberty/pex-unix.c
index 35a545cb17..c92a429797 100644
--- a/libiberty/pex-unix.c
+++ b/libiberty/pex-unix.c
@@ -277,6 +277,7 @@ static int pex_unix_wait (struct pex_obj *, long, int *, struct pex_time *,
 			  int, const char **, int *);
 static int pex_unix_pipe (struct pex_obj *, int *, int);
 static FILE *pex_unix_fdopenr (struct pex_obj *, int, int);
+static FILE *pex_unix_fdopenw (struct pex_obj *, int, int);
 static void pex_unix_cleanup (struct pex_obj *);
 
 /* The list of functions we pass to the common routines.  */
@@ -290,6 +291,7 @@ const struct pex_funcs funcs =
   pex_unix_wait,
   pex_unix_pipe,
   pex_unix_fdopenr,
+  pex_unix_fdopenw,
   pex_unix_cleanup
 };
 
@@ -495,6 +497,15 @@ pex_unix_fdopenr (struct pex_obj *obj ATTRIBUTE_UNUSED, int fd,
   return fdopen (fd, "r");
 }
 
+static FILE *
+pex_unix_fdopenw (struct pex_obj *obj ATTRIBUTE_UNUSED, int fd,
+		  int binary ATTRIBUTE_UNUSED)
+{
+  if (fcntl (fd, F_SETFD, FD_CLOEXEC) < 0)
+    return NULL;
+  return fdopen (fd, "w");
+}
+
 static void
 pex_unix_cleanup (struct pex_obj *obj ATTRIBUTE_UNUSED)
 {
diff --git a/libiberty/pex-win32.c b/libiberty/pex-win32.c
index 3a75c5be00..046f393c6d 100644
--- a/libiberty/pex-win32.c
+++ b/libiberty/pex-win32.c
@@ -83,6 +83,7 @@ static int pex_win32_wait (struct pex_obj *, long, int *,
 			   struct pex_time *, int, const char **, int *);
 static int pex_win32_pipe (struct pex_obj *, int *, int);
 static FILE *pex_win32_fdopenr (struct pex_obj *, int, int);
+static FILE *pex_win32_fdopenw (struct pex_obj *, int, int);
 
 /* The list of functions we pass to the common routines.  */
 
@@ -95,6 +96,7 @@ const struct pex_funcs funcs =
   pex_win32_wait,
   pex_win32_pipe,
   pex_win32_fdopenr,
+  pex_win32_fdopenw,
   NULL /* cleanup */
 };
 
@@ -766,6 +768,18 @@ pex_win32_fdopenr (struct pex_obj *obj ATTRIBUTE_UNUSED, int fd,
   return fdopen (fd, binary ? "rb" : "r");
 }
 
+static FILE *
+pex_win32_fdopenw (struct pex_obj *obj ATTRIBUTE_UNUSED, int fd,
+		   int binary)
+{
+  HANDLE h = (HANDLE) _get_osfhandle (fd);
+  if (h == INVALID_HANDLE_VALUE)
+    return NULL;
+  if (! SetHandleInformation (h, HANDLE_FLAG_INHERIT, 0))
+    return NULL;
+  return fdopen (fd, binary ? "wb" : "w");
+}
+
 #ifdef MAIN
 #include <stdio.h>
 
diff --git a/libiberty/pexecute.txh b/libiberty/pexecute.txh
index 461ff33d01..7d45576eec 100644
--- a/libiberty/pexecute.txh
+++ b/libiberty/pexecute.txh
@@ -1,3 +1,4 @@
+@c -*- mode: texinfo -*-
 @deftypefn Extension {struct pex_obj *} pex_init (int @var{flags}, const char *@var{pname}, const char *@var{tempbase})
 
 Prepare to execute one or more programs, with standard output of each
@@ -129,6 +130,67 @@ value, or to 0 if there is no relevant @code{errno}.
 
 @end deftypefn
 
+@deftypefn Extension {FILE *} pex_input_file (struct pex_obj *@var{obj}, int @var{flags}, const char *@var{in_name})
+
+Return a stream for a temporary file to pass to the first program in
+the pipeline as input.
+
+The name of the input file is chosen according to the same rules
+@code{pex_run} uses to choose output file names, based on
+@var{in_name}, @var{obj} and the @code{PEX_SUFFIX} bit in @var{flags}.
+
+Don't call @code{fclose} on the returned stream; the first call to
+@code{pex_run} closes it automatically.
+
+If @var{flags} includes @code{PEX_BINARY_OUTPUT}, open the stream in
+binary mode; otherwise, open it in the default mode.  Including
+@code{PEX_BINARY_OUTPUT} in @var{flags} has no effect on Unix.
+@end deftypefn
+
+@deftypefn Extension {FILE *} pex_input_pipe (struct pex_obj *@var{obj}, int @var{binary})
+
+Return a stream @var{fp} for a pipe connected to the standard input of
+the first program in the pipeline; @var{fp} is opened for writing.
+You must have passed @code{PEX_USE_PIPES} to the @code{pex_init} call
+that returned @var{obj}.
+
+You must close @var{fp} using @code{fclose} yourself when you have
+finished writing data to the pipeline.
+
+The file descriptor underlying @var{fp} is marked not to be inherited
+by child processes.
+
+On systems that do not support pipes, this function returns
+@code{NULL}, and sets @code{errno} to @code{EINVAL}.  If you would
+like to write code that is portable to all systems the @code{pex}
+functions support, consider using @code{pex_input_file} instead.
+
+There are two opportunities for deadlock using
+@code{pex_input_pipe}:
+
+@itemize @bullet
+@item
+Most systems' pipes can buffer only a fixed amount of data; a process
+that writes to a full pipe blocks.  Thus, if you write to @file{fp}
+before starting the first process, you run the risk of blocking when
+there is no child process yet to read the data and allow you to
+continue.  @code{pex_input_pipe} makes no promises about the
+size of the pipe's buffer, so if you need to write any data at all
+before starting the first process in the pipeline, consider using
+@code{pex_input_file} instead.
+
+@item
+Using @code{pex_input_pipe} and @code{pex_read_output} together
+may also cause deadlock.  If the output pipe fills up, so that each
+program in the pipeline is waiting for the next to read more data, and
+you fill the input pipe by writing more data to @var{fp}, then there
+is no way to make progress: the only process that could read data from
+the output pipe is you, but you are blocked on the input pipe.
+
+@end itemize
+
+@end deftypefn
+
 @deftypefn Extension {FILE *} pex_read_output (struct pex_obj *@var{obj}, int @var{binary})
 
 Returns a @code{FILE} pointer which may be used to read the standard