libio: fmemopen rewrite to POSIX compliance

This patch added a new fmemopen version, for glibc 2.22, that aims to be
POSIX complaint.  It fixes some long-stading glibc fmemopen issues, such
as:

* it changes the way fseek with SEEK_END works on fmemopen to seek
  relative to buffer size instead of first '\0'.  This is default mode and
  'b' opening mode does not change internal behavior (bz#6544).

* fix apending opening mode to use as start position either first null
  byte of len specified in function call (bz#13152 and #13151).

* remove binary option 'b' and internal different handling (bz#12836)

* fix seek/SEE_END with negative values (bz#14292).

A compatibility symbol is provided to with old behavior for older symbols
version (2.2.5).

	* include/stdio.h (fmemopen): Remove hidden prototype.
	(__fmemopen): Add new hidden prototype.
	* libio/Makefile: Add oldfmemopen object.
	* libio/Versions [GLIBC_2.22]: Add new fmemopen symbol.
	* libio/fmemopen.c (__fmemopen): Function rewrite to be POSIX
	compliance.
	* libio/oldfmemopen.c: New file: old fmemopen implementation for
	symbol compatibility.
	* stdio-common/Makefile [tests]: Add new tst-fmemopen3.
	* stdio-common/psiginfo.c [psiginfo]: Call __fmemopen instead of
	fmemopen.
	* stdio-common/tst-fmemopen3.c: New file: more fmemopen tests, focus
	on append and read mode.
	* sysdeps/unix/sysv/linux/aarch64/libc.abilist [GLIBC_2.22]: Add
	fmemopen.
	* sysdeps/unix/sysv/linux/alpha/libc.abilist [GLIBC_2.22]: Likewise.
	* sysdeps/unix/sysv/linux/arm/libc.abilist [GLIBC_2.22]: Likewise.
	* sysdeps/unix/sysv/linux/i386/libc.abilist [GLIBC_2.22]: Likewise.
	* sysdeps/unix/sysv/linux/ia64/libc.abilist [GLIBC_2.22]:
	Likewise.
	* sysdeps/unix/sysv/linux/m68k/coldfire/libc.abilist
	[GLIBC_2.22]: Likewise.
	* sysdeps/unix/sysv/linux/m68k/m680x0/libc.abilist [GLIBC_2.22]:
	Likewise.
	* sysdeps/unix/sysv/linux/microblaze/libc.abilist [GLIBC_2.22]:
	Likewise.
	* sysdeps/unix/sysv/linux/mips/mips32/fpu/libc.abilist
	[GLIBC_2.22]: Likewise.
	* sysdeps/unix/sysv/linux/mips/mips32/nofpu/libc.abilist
	[GLIBC_2.22]: Likewise.
	* sysdeps/unix/sysv/linux/mips/mips64/n32/libc.abilist
	[GLIBC_2.22]: Likewise.
	* sysdeps/unix/sysv/linux/mips/mips64/n64/libc.abilist
	[GLIBC_2.22]: Likewise.
	* sysdeps/unix/sysv/linux/powerpc/powerpc32/fpu/libc.abilist
	[GLIBC_2.22]: Likewise.
	* sysdeps/unix/sysv/linux/powerpc/powerpc32/nofpu/libc.abilist
	[GLIBC_2.22]: Likewise.
	* sysdeps/unix/sysv/linux/powerpc/powerpc64/libc.abilist
	[GLIBC_2.22]: Likewise.
	* sysdeps/unix/sysv/linux/s390/s390-32/libc.abilist [GLIBC_2.22]:
	Likewise.
	* sysdeps/unix/sysv/linux/s390/s390-64/libc.abilist [GLIBC_2.22]:
	Likewise.
	* sysdeps/unix/sysv/linux/sh/libc.abilist [GLIBC_2.22]: Likewise.
	* sysdeps/unix/sysv/linux/sparc/sparc32/libc.abilist
	[GLIBC_2.22]: Likewise.
	* sysdeps/unix/sysv/linux/sparc/sparc64/libc.abilist
	[GLIBC_2.22]: Likewise.
	* sysdeps/unix/sysv/linux/tile/tilegx/tilegx32/libc.abilist
	[GLIBC_2.22]: Likewise.
	* sysdeps/unix/sysv/linux/tile/tilegx/tilegx64/libc.abilist
	[GLIBC_2.22]: Likewise.
	* sysdeps/unix/sysv/linux/tile/tilepro/libc.abilist [GLIBC_2.22]:
	Likewise.
	* sysdeps/unix/sysv/linux/x86_64/64/libc.abilist [GLIBC_2.22]:
	Likewise.
	* sysdeps/unix/sysv/linux/x86_64/x32/libc.abilist [GLIBC_2.22]:
	Likewise.
	* sysdeps/unix/sysv/linux/hppa/libc.abilist [GLIBC_2.22]: Likewise.
	* sysdeps/unix/sysv/linux/nios2/libc.abilist [GLIBC_2.22]: Likewise.

1 files changed, 47 insertions, 93 deletions

diff --git a/libio/fmemopen.c b/libio/fmemopen.c
index 06e5ab8002..e6e6a49f76 100644
--- a/libio/fmemopen.c
+++ b/libio/fmemopen.c
@@ -1,7 +1,6 @@
-/* Fmemopen implementation.
-   Copyright (C) 2000-2015 Free Software Foundation, Inc.
+/* fmemopen implementation.
+   Copyright (C) 2015 Free Software Foundation, Inc.
    This file is part of the GNU C Library.
-   Contributed by Hanno Mueller, kontakt@hanno.de, 2000.
 
    The GNU C Library is free software; you can redistribute it and/or
    modify it under the terms of the GNU Lesser General Public
@@ -17,54 +16,10 @@
    License along with the GNU C Library; if not, see
    <http://www.gnu.org/licenses/>.  */
 
-/*
- * fmemopen() - "my" version of a string stream
- * Hanno Mueller, kontakt@hanno.de
- *
- *
- * I needed fmemopen() for an application that I currently work on,
- * but couldn't find it in libio. The following snippet of code is an
- * attempt to implement what glibc's documentation describes.
- *
- *
- *
- * I already see some potential problems:
- *
- * - I never used the "original" fmemopen(). I am sure that "my"
- *   fmemopen() behaves differently than the original version.
- *
- * - The documentation doesn't say wether a string stream allows
- *   seeks. I checked the old fmemopen implementation in glibc's stdio
- *   directory, wasn't quite able to see what is going on in that
- *   source, but as far as I understand there was no seek there. For
- *   my application, I needed fseek() and ftell(), so it's here.
- *
- * - "append" mode and fseek(p, SEEK_END) have two different ideas
- *   about the "end" of the stream.
- *
- *   As described in the documentation, when opening the file in
- *   "append" mode, the position pointer will be set to the first null
- *   character of the string buffer (yet the buffer may already
- *   contain more data). For fseek(), the last byte of the buffer is
- *   used as the end of the stream.
- *
- * - It is unclear to me what the documentation tries to say when it
- *   explains what happens when you use fmemopen with a NULL
- *   buffer.
- *
- *   Quote: "fmemopen [then] allocates an array SIZE bytes long. This
- *   is really only useful if you are going to write things to the
- *   buffer and then read them back in again."
- *
- *   What does that mean if the original fmemopen() did not allow
- *   seeking? How do you read what you just wrote without seeking back
- *   to the beginning of the stream?
- *
- * - I think there should be a second version of fmemopen() that does
- *   not add null characters for each write. (At least in my
- *   application, I am not actually using strings but binary data and
- *   so I don't need the stream to add null characters on its own.)
- */
+/* fmemopen() from 2.22 and forward works as defined by POSIX.  It also
+   provides an older symbol, version 2.2.5, that behaves different regarding
+   SEEK_END (libio/oldfmemopen.c).  */
+
 
 #include <errno.h>
 #include <libio.h>
@@ -79,25 +34,23 @@
 typedef struct fmemopen_cookie_struct fmemopen_cookie_t;
 struct fmemopen_cookie_struct
 {
-  char *buffer;
-  int mybuffer;
-  int binmode;
-  size_t size;
-  _IO_off64_t pos;
-  size_t maxpos;
+  char        *buffer;   /* memory buffer.  */
+  int         mybuffer;  /* allocated my buffer?  */
+  int         append;    /* buffer open for append?  */
+  size_t      size;      /* buffer length in bytes.  */
+  _IO_off64_t pos;       /* current position at the buffer.  */
+  size_t      maxpos;    /* max position in buffer.  */
 };
 
 
 static ssize_t
 fmemopen_read (void *cookie, char *b, size_t s)
 {
-  fmemopen_cookie_t *c;
-
-  c = (fmemopen_cookie_t *) cookie;
+  fmemopen_cookie_t *c = (fmemopen_cookie_t *) cookie;
 
-  if (c->pos + s > c->size)
+  if (c->pos + s > c->maxpos)
     {
-      if ((size_t) c->pos == c->size)
+      if ((size_t) c->pos == c->maxpos)
 	return 0;
       s = c->size - c->pos;
     }
@@ -115,29 +68,28 @@ fmemopen_read (void *cookie, char *b, size_t s)
 static ssize_t
 fmemopen_write (void *cookie, const char *b, size_t s)
 {
-  fmemopen_cookie_t *c;
+  fmemopen_cookie_t *c = (fmemopen_cookie_t *) cookie;;
+  _IO_off64_t pos = c->append ? c->maxpos : c->pos;
   int addnullc;
 
-  c = (fmemopen_cookie_t *) cookie;
-
-  addnullc = c->binmode == 0 && (s == 0 || b[s - 1] != '\0');
+  addnullc = (s == 0 || b[s - 1] != '\0');
 
-  if (c->pos + s + addnullc > c->size)
+  if (pos + s + addnullc > c->size)
     {
       if ((size_t) (c->pos + addnullc) >= c->size)
 	{
 	  __set_errno (ENOSPC);
 	  return 0;
 	}
-      s = c->size - c->pos - addnullc;
+      s = c->size - pos - addnullc;
     }
 
-  memcpy (&(c->buffer[c->pos]), b, s);
+  memcpy (&(c->buffer[pos]), b, s);
 
-  c->pos += s;
-  if ((size_t) c->pos > c->maxpos)
+  pos += s;
+  if ((size_t) pos > c->maxpos)
     {
-      c->maxpos = c->pos;
+      c->maxpos = pos;
       if (addnullc)
 	c->buffer[c->maxpos] = '\0';
     }
@@ -150,9 +102,7 @@ static int
 fmemopen_seek (void *cookie, _IO_off64_t *p, int w)
 {
   _IO_off64_t np;
-  fmemopen_cookie_t *c;
-
-  c = (fmemopen_cookie_t *) cookie;
+  fmemopen_cookie_t *c = (fmemopen_cookie_t *) cookie;
 
   switch (w)
     {
@@ -165,7 +115,7 @@ fmemopen_seek (void *cookie, _IO_off64_t *p, int w)
       break;
 
     case SEEK_END:
-      np = (c->binmode ? c->size : c->maxpos) - *p;
+      np = c->maxpos + *p;
       break;
 
     default:
@@ -184,9 +134,7 @@ fmemopen_seek (void *cookie, _IO_off64_t *p, int w)
 static int
 fmemopen_close (void *cookie)
 {
-  fmemopen_cookie_t *c;
-
-  c = (fmemopen_cookie_t *) cookie;
+  fmemopen_cookie_t *c = (fmemopen_cookie_t *) cookie;
 
   if (c->mybuffer)
     free (c->buffer);
@@ -197,18 +145,11 @@ fmemopen_close (void *cookie)
 
 
 FILE *
-fmemopen (void *buf, size_t len, const char *mode)
+__fmemopen (void *buf, size_t len, const char *mode)
 {
   cookie_io_functions_t iof;
   fmemopen_cookie_t *c;
 
-  if (__glibc_unlikely (len == 0))
-    {
-    einval:
-      __set_errno (EINVAL);
-      return NULL;
-    }
-
   c = (fmemopen_cookie_t *) malloc (sizeof (fmemopen_cookie_t));
   if (c == NULL)
     return NULL;
@@ -231,26 +172,38 @@ fmemopen (void *buf, size_t len, const char *mode)
       if (__glibc_unlikely ((uintptr_t) len > -(uintptr_t) buf))
 	{
 	  free (c);
-	  goto einval;
+	  __set_errno (EINVAL);
+	  return NULL;
 	}
 
       c->buffer = buf;
 
-      if (mode[0] == 'w')
+      /* POSIX states that w+ mode should truncate the buffer.  */
+      if (mode[0] == 'w' && mode[1] == '+')
 	c->buffer[0] = '\0';
 
       c->maxpos = strnlen (c->buffer, len);
     }
 
+
+  /* Mode   |  starting position (cookie::pos) |          size (cookie::size)
+     ------ |----------------------------------|-----------------------------
+     read   |          beginning of the buffer |                size argument
+     write  |          beginning of the buffer |                         zero
+     append |    first null or size buffer + 1 |  first null or size argument
+   */
+
   c->size = len;
 
-  if (mode[0] == 'a')
+  if (mode[0] == 'r')
+    c->maxpos = len;
+
+  c->append = mode[0] == 'a';
+  if (c->append)
     c->pos = c->maxpos;
   else
     c->pos = 0;
 
-  c->binmode = mode[0] != '\0' && mode[1] == 'b';
-
   iof.read = fmemopen_read;
   iof.write = fmemopen_write;
   iof.seek = fmemopen_seek;
@@ -258,4 +211,5 @@ fmemopen (void *buf, size_t len, const char *mode)
 
   return _IO_fopencookie (c, mode, iof);
 }
-libc_hidden_def (fmemopen)
+libc_hidden_def (__fmemopen)
+versioned_symbol (libc, __fmemopen, fmemopen, GLIBC_2_22);