libc/stdio: Rework custom streams interface similar to glibc.

Save 20 bytes per FILE structure, avoid indirect call for
read/write/seek/close operations for normal streams.
Additionally, custom streams has fileno = -2 now, like in glibc.

bloat-o-meter report (UCLIBC_HAS_GLIBC_CUSTOM_STREAMS=y):
function                                             old     new   delta
fopencookie                                           69     131     +62
ftello64                                             233     260     +27
fseeko64                                             298     319     +21
fclose                                               423     442     +19
.rodata                                            16696   16708     +12
fileno_unlocked                                       53      45      -8
__ns_name_pack                                       859     851      -8
vswscanf                                             184     144     -40
vdprintf                                             231     187     -44
vsscanf                                              210     151     -59
vswprintf                                            269     201     -68
vsnprintf                                            249     181     -68
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 5/7 up/down: 141/-295)         Total: -154 bytes

Signed-off-by: Leonid Lisovskiy <lly.dev@gmail.com>
Signed-off-by: Waldemar Brodkorb <wbx@uclibc-ng.org>

17 files changed, 155 insertions, 205 deletions

diff --git a/libc/stdio/_READ.c b/libc/stdio/_READ.c
index 02601c090..a548dbb3f 100644
--- a/libc/stdio/_READ.c
+++ b/libc/stdio/_READ.c
@@ -27,7 +27,7 @@ size_t attribute_hidden __stdio_READ(register FILE *stream,
 	ssize_t rv = 0;
 
 	__STDIO_STREAM_VALIDATE(stream);
-	assert(stream->__filedes >= -1);
+	assert(stream->__filedes >= -2);
 	assert(__STDIO_STREAM_IS_READING(stream));
 	assert(!__STDIO_STREAM_BUFFER_RAVAIL(stream)); /* Buffer must be empty. */
 	assert(!(stream->__modeflags & __FLAG_UNGOT));
diff --git a/libc/stdio/_WRITE.c b/libc/stdio/_WRITE.c
index 6af5da8e4..712236f8f 100644
--- a/libc/stdio/_WRITE.c
+++ b/libc/stdio/_WRITE.c
@@ -36,7 +36,7 @@ size_t attribute_hidden __stdio_WRITE(register FILE *stream,
 	ssize_t rv, stodo;
 
 	__STDIO_STREAM_VALIDATE(stream);
-	assert(stream->__filedes >= -1);
+	assert(stream->__filedes >= -2);
 	assert(__STDIO_STREAM_IS_WRITING(stream));
 	assert(!__STDIO_STREAM_BUFFER_WUSED(stream)); /* Buffer must be empty. */
 
diff --git a/libc/stdio/_cs_funcs.c b/libc/stdio/_cs_funcs.c
index 9df93f227..be416a450 100644
--- a/libc/stdio/_cs_funcs.c
+++ b/libc/stdio/_cs_funcs.c
@@ -8,46 +8,6 @@
 #include "_stdio.h"
 
 /**********************************************************************/
-#ifdef __UCLIBC_HAS_GLIBC_CUSTOM_STREAMS__
-/**********************************************************************/
-
-ssize_t attribute_hidden _cs_read(void *cookie, char *buf, size_t bufsize)
-{
-	return read(*((int *) cookie), buf, bufsize);
-}
-
-/**********************************************************************/
-
-ssize_t attribute_hidden _cs_write(void *cookie, const char *buf, size_t bufsize)
-{
-	return write(*((int *) cookie), (char *) buf, bufsize);
-}
-
-/**********************************************************************/
-
-int attribute_hidden _cs_seek(void *cookie, register __offmax_t *pos, int whence)
-{
-	__offmax_t res;
-
-#ifdef __UCLIBC_HAS_LFS__
-	res = lseek64(*((int *) cookie), *pos, whence);
-#else
-	res = lseek(*((int *) cookie), *pos, whence);
-#endif
-
-	return (res >= 0) ? ((*pos = res), 0) : ((int) res);
-}
-
-/**********************************************************************/
-
-int attribute_hidden _cs_close(void *cookie)
-{
-	return close(*((int *) cookie));
-}
-
-/**********************************************************************/
-#else
-/**********************************************************************/
 
 int attribute_hidden __stdio_seek(FILE *stream, register __offmax_t *pos, int whence)
 {
@@ -63,5 +23,3 @@ int attribute_hidden __stdio_seek(FILE *stream, register __offmax_t *pos, int wh
 }
 
 /**********************************************************************/
-#endif
-/**********************************************************************/
diff --git a/libc/stdio/_fopen.c b/libc/stdio/_fopen.c
index 5bc61cf39..be05c48a5 100644
--- a/libc/stdio/_fopen.c
+++ b/libc/stdio/_fopen.c
@@ -192,8 +192,6 @@ FILE attribute_hidden *_stdio_fopen(intptr_t fname_or_mode,
 	__STDIO_STREAM_INIT_BUFREAD_BUFPOS(stream);
 #endif
 
-	__STDIO_STREAM_RESET_GCS(stream);
-
 #ifdef __UCLIBC_HAS_WCHAR__
 	stream->__ungot_width[0] = 0;
 #endif
diff --git a/libc/stdio/_rfill.c b/libc/stdio/_rfill.c
index d61b1a9f9..e9d2fa698 100644
--- a/libc/stdio/_rfill.c
+++ b/libc/stdio/_rfill.c
@@ -24,7 +24,7 @@ size_t attribute_hidden __stdio_rfill(register FILE *__restrict stream)
 	size_t rv;
 
 	__STDIO_STREAM_VALIDATE(stream);
-	assert(stream->__filedes >= -1);
+	assert(stream->__filedes >= -2);
 	assert(__STDIO_STREAM_IS_READING(stream));
 	assert(!__STDIO_STREAM_BUFFER_RAVAIL(stream)); /* Buffer must be empty. */
 	assert(__STDIO_STREAM_BUFFER_SIZE(stream));	/* Must have a buffer. */
diff --git a/libc/stdio/_scanf.c b/libc/stdio/_scanf.c
index f2a96700b..80e49567f 100644
--- a/libc/stdio/_scanf.c
+++ b/libc/stdio/_scanf.c
@@ -202,15 +202,6 @@ int vsscanf(const char *sp, const char *fmt, va_list ap)
 {
 	FILE f;
 
-/* 	__STDIO_STREAM_RESET_GCS(&f); */
-#ifdef __UCLIBC_HAS_GLIBC_CUSTOM_STREAMS__
-	f.__cookie = &(f.__filedes);
-	f.__gcs.read = NULL;
-	f.__gcs.write = NULL;
-	f.__gcs.seek = NULL;
-	f.__gcs.close = NULL;
-#endif
-
 	f.__filedes = __STDIO_STREAM_FAKE_VSSCANF_FILEDES;
 	f.__modeflags = (__FLAG_NARROW|__FLAG_READONLY|__FLAG_READING);
 
@@ -249,15 +240,6 @@ int vsscanf(const char *sp, const char *fmt, va_list ap)
 	f.bufpos = (unsigned char *) ((void *) sp);
 	f.bufread = f.bufpos + strlen(sp);
 
-/* 	__STDIO_STREAM_RESET_GCS(&f.f); */
-#ifdef __UCLIBC_HAS_GLIBC_CUSTOM_STREAMS__
-	f.f.__cookie = &(f.f.__filedes);
-	f.f.__gcs.read = NULL;
-	f.f.__gcs.write = NULL;
-	f.f.__gcs.seek = NULL;
-	f.f.__gcs.close = NULL;
-#endif
-
 	f.f.__filedes = __STDIO_STREAM_FAKE_VSSCANF_FILEDES_NB;
 	f.f.__modeflags = (__FLAG_NARROW|__FLAG_READONLY|__FLAG_READING);
 
@@ -383,15 +365,6 @@ int vswscanf(const wchar_t * __restrict str, const wchar_t * __restrict format,
 	__STDIO_STREAM_DISABLE_GETC(&f);
 	__STDIO_STREAM_DISABLE_PUTC(&f);
 
-/* 	__STDIO_STREAM_RESET_GCS(&f); */
-#ifdef __UCLIBC_HAS_GLIBC_CUSTOM_STREAMS__
-	f.__cookie = &(f.__filedes);
-	f.__gcs.read = NULL;
-	f.__gcs.write = NULL;
-	f.__gcs.seek = NULL;
-	f.__gcs.close = NULL;
-#endif
-
 	f.__filedes = __STDIO_STREAM_FAKE_VSWSCANF_FILEDES;
 	f.__modeflags = (__FLAG_WIDE|__FLAG_READONLY|__FLAG_READING);
 
diff --git a/libc/stdio/_stdio.c b/libc/stdio/_stdio.c
index ee247a5fd..2a1054618 100644
--- a/libc/stdio/_stdio.c
+++ b/libc/stdio/_stdio.c
@@ -51,13 +51,6 @@
 #define __STDIO_FILE_INIT_BUFFERS(buf,bufsize)
 #endif
 
-#ifdef __UCLIBC_HAS_GLIBC_CUSTOM_STREAMS__
-#define __STDIO_FILE_INIT_CUSTOM_STREAM(stream) \
-	&((stream).__filedes), { _cs_read, _cs_write, _cs_seek, _cs_close },
-#else
-#define __STDIO_FILE_INIT_CUSTOM_STREAM(stream)
-#endif
-
 #ifdef __STDIO_MBSTATE
 #define __STDIO_FILE_INIT_MBSTATE \
 	{ 0, 0 },
@@ -92,7 +85,6 @@
 	__STDIO_FILE_INIT_BUFGETC((buf)) \
 	__STDIO_FILE_INIT_BUFPUTC((buf)) \
 	__STDIO_FILE_INIT_NEXT(next) \
-	__STDIO_FILE_INIT_CUSTOM_STREAM(stream) \
 	__STDIO_FILE_INIT_WUNGOT \
 	__STDIO_FILE_INIT_MBSTATE \
 	__STDIO_FILE_INIT_UNUSED \
@@ -240,7 +232,7 @@ void _stdio_term(void)
 #endif
 #ifdef __UCLIBC_HAS_GLIBC_CUSTOM_STREAMS__
 		/* Actually close all custom streams to perform any special cleanup. */
-		if (ptr->__cookie != &ptr->__filedes) {
+		if (__STDIO_STREAM_IS_CUSTOM(ptr)) {
 			__CLOSE(ptr);
 		}
 #endif
@@ -284,14 +276,9 @@ void attribute_hidden _stdio_validate_FILE(const FILE *stream)
 #endif
 
 #warning Define a constant for minimum possible valid __filedes?
-	assert(stream->__filedes >= -3);
+	assert(stream->__filedes >= -4);
 
 	if (stream->__filedes < 0) {
-/* 		assert((stream->__filedes != -1) */
-/* #ifdef __UCLIBC_HAS_GLIBC_CUSTOM_STREAMS__ */
-/* 			   || (stream->__cookie == &stream->__filedes) /\* custom *\/ */
-/* #endif */
-/* 			   ); */
 /* 		assert((stream->__filedes == -1) || __STDIO_STREAM_IS_FBF(stream)); */
 
 		assert(!__STDIO_STREAM_IS_FAKE_VSNPRINTF(stream)
@@ -308,12 +295,6 @@ void attribute_hidden _stdio_validate_FILE(const FILE *stream)
 #endif
 	}
 
-#ifdef __UCLIBC_HAS_GLIBC_CUSTOM_STREAMS__
-	if (stream->__cookie != &stream->__filedes) { /* custom */
-		assert(stream->__filedes == -1);
-	}
-#endif
-
 	/* Can not be both narrow and wide oriented at the same time. */
 	assert(!(__STDIO_STREAM_IS_NARROW(stream)
 			 && __STDIO_STREAM_IS_WIDE(stream)));
diff --git a/libc/stdio/_stdio.h b/libc/stdio/_stdio.h
index 94557c257..310510d66 100644
--- a/libc/stdio/_stdio.h
+++ b/libc/stdio/_stdio.h
@@ -4,6 +4,8 @@
  *
  * Dedicated to Toni.  See uClibc/DEDICATION.mjn3 for details.
  */
+#ifndef __STDIO_H_I
+#define __STDIO_H_I 1
 
 #include <features.h>
 #include <assert.h>
@@ -96,48 +98,61 @@ do { \
 /**********************************************************************/
 #ifdef __UCLIBC_HAS_GLIBC_CUSTOM_STREAMS__
 
-extern __ssize_t _cs_read(void *cookie, char *buf, size_t bufsize) attribute_hidden;
-extern __ssize_t _cs_write(void *cookie, const char *buf, size_t bufsize) attribute_hidden;
-extern int _cs_seek(void *cookie, __offmax_t *pos, int whence) attribute_hidden;
-extern int _cs_close(void *cookie) attribute_hidden;
-
-#define __STDIO_STREAM_RESET_GCS(S) \
-	(S)->__cookie = &((S)->__filedes); \
-	(S)->__gcs.read = _cs_read; \
-	(S)->__gcs.write = _cs_write; \
-	(S)->__gcs.seek = _cs_seek; \
-	(S)->__gcs.close = _cs_close
-
-
-#define __READ(STREAMPTR,BUF,SIZE) \
-	((((STREAMPTR)->__gcs.read) == NULL) ? -1 : \
-	(((STREAMPTR)->__gcs.read)((STREAMPTR)->__cookie,(BUF),(SIZE))))
-#define __WRITE(STREAMPTR,BUF,SIZE) \
-	((((STREAMPTR)->__gcs.write) == NULL) ? -1 : \
-	(((STREAMPTR)->__gcs.write)((STREAMPTR)->__cookie,(BUF),(SIZE))))
-#define __SEEK(STREAMPTR,PPOS,WHENCE) \
-	((((STREAMPTR)->__gcs.seek) == NULL) ? -1 : \
-	(((STREAMPTR)->__gcs.seek)((STREAMPTR)->__cookie,(PPOS),(WHENCE))))
-#define __CLOSE(STREAMPTR) \
-	((((STREAMPTR)->__gcs.close) == NULL) ? 0 : \
-	(((STREAMPTR)->__gcs.close)((STREAMPTR)->__cookie)))
+#define __STDIO_STREAM_GLIBC_CUSTOM_FILEDES		(-2)
+
+#define __STDIO_STREAM_IS_CUSTOM(S) \
+	((S)->__filedes == __STDIO_STREAM_GLIBC_CUSTOM_FILEDES)
+
+#define __STDIO_STREAM_CUSTOM_IO_FUNC(S, NAME, RC, ARGS...) \
+ if (__STDIO_STREAM_IS_CUSTOM((S))) { \
+	_IO_cookie_file_t *cfile = (_IO_cookie_file_t *) (S); \
+	return (cfile->__gcs.NAME == NULL) ? (RC) : \
+		cfile->__gcs.NAME(cfile->__cookie, ##ARGS); \
+ }
+
+typedef struct {
+  struct __STDIO_FILE_STRUCT __fp;
+  void *__cookie;
+  _IO_cookie_io_functions_t __gcs;
+} _IO_cookie_file_t;
 
 #else  /* __UCLIBC_HAS_GLIBC_CUSTOM_STREAMS__ */
 
+#undef __STDIO_STREAM_GLIBC_CUSTOM_FILEDES
+#define __STDIO_STREAM_IS_CUSTOM(S)	(0)
+#define __STDIO_STREAM_CUSTOM_IO_FUNC(S, NAME, RC, ARGS...)
+
+#endif /* __UCLIBC_HAS_GLIBC_CUSTOM_STREAMS__ */
+
 extern int __stdio_seek(FILE *stream, register __offmax_t *pos, int whence) attribute_hidden;
 
-#define __STDIO_STREAM_RESET_GCS(S) ((void)0)
+static inline ssize_t __READ(FILE *stream, char *buf, size_t bufsize)
+{
+	__STDIO_STREAM_CUSTOM_IO_FUNC(stream, read, -1, buf, bufsize);
 
-#define __READ(STREAMPTR,BUF,SIZE) \
-	(read((STREAMPTR)->__filedes,(BUF),(SIZE)))
-#define __WRITE(STREAMPTR,BUF,SIZE) \
-	(write((STREAMPTR)->__filedes,(BUF),(SIZE)))
-#define __SEEK(STREAMPTR,PPOS,WHENCE) \
-	(__stdio_seek((STREAMPTR),(PPOS),(WHENCE)))
-#define __CLOSE(STREAMPTR) \
-	(close((STREAMPTR)->__filedes))
+	return read(stream->__filedes, buf, bufsize);
+}
 
-#endif /* __UCLIBC_HAS_GLIBC_CUSTOM_STREAMS__ */
+static inline ssize_t __WRITE(FILE *stream, const char *buf, size_t bufsize)
+{
+	__STDIO_STREAM_CUSTOM_IO_FUNC(stream, write, -1, buf, bufsize);
+
+	return write(stream->__filedes, buf, bufsize);
+}
+
+static inline int __SEEK(FILE *stream, register __offmax_t *pos, int whence)
+{
+	__STDIO_STREAM_CUSTOM_IO_FUNC(stream, seek, -1, pos, whence);
+
+	return __stdio_seek(stream, pos, whence);
+}
+
+static inline int __CLOSE(FILE *stream)
+{
+	__STDIO_STREAM_CUSTOM_IO_FUNC(stream, close, 0);
+
+	return close(stream->__filedes);
+}
 
 /**********************************************************************/
 #ifdef __UCLIBC_HAS_WCHAR__
@@ -254,12 +269,6 @@ extern int __stdio_seek(FILE *stream, register __offmax_t *pos, int whence) attr
 # define __STDIO_STREAM_CAN_USE_BUFFER_ADD(S)		(0)
 #endif
 
-#ifdef __UCLIBC_HAS_GLIBC_CUSTOM_STREAMS__
-#define __STDIO_STREAM_IS_CUSTOM(S)		((S)->__cookie != &((S)->__filedes))
-#else
-#define __STDIO_STREAM_IS_CUSTOM(S)			(0)
-#endif
-
 /**********************************************************************/
 
 #ifdef __STDIO_BUFFERS
@@ -346,10 +355,10 @@ extern void _store_inttype(void *dest, int desttype, uintmax_t val) attribute_hi
 	(S)->__bufread = (S)->__bufpos = (S)->__bufstart
 
 
-#define __STDIO_STREAM_FAKE_VSNPRINTF_FILEDES		(-2)
-#define __STDIO_STREAM_FAKE_VSSCANF_FILEDES		(-2)
-#define __STDIO_STREAM_FAKE_VSWPRINTF_FILEDES		(-3)
-#define __STDIO_STREAM_FAKE_VSWSCANF_FILEDES		(-3)
+#define __STDIO_STREAM_FAKE_VSNPRINTF_FILEDES		(-3)
+#define __STDIO_STREAM_FAKE_VSSCANF_FILEDES		(-3)
+#define __STDIO_STREAM_FAKE_VSWPRINTF_FILEDES		(-4)
+#define __STDIO_STREAM_FAKE_VSWSCANF_FILEDES		(-4)
 
 #define __STDIO_STREAM_IS_FAKE_VSNPRINTF(S) \
 	((S)->__filedes == __STDIO_STREAM_FAKE_VSNPRINTF_FILEDES)
@@ -386,6 +395,7 @@ extern void _store_inttype(void *dest, int desttype, uintmax_t val) attribute_hi
 #define __STDIO_STREAM_IS_FAKE_VSNPRINTF(S)			(0)
 #define __STDIO_STREAM_IS_FAKE_VSSCANF(S)			(0)
 #undef __STDIO_STREAM_IS_FAKE_VSWPRINTF
+#undef __STDIO_STREAM_IS_FAKE_VSWSCANF
 
 # ifdef __USE_OLD_VFPRINTF__
 #  define __STDIO_STREAM_FAKE_VSNPRINTF_FILEDES_NB		(-2)
@@ -461,3 +471,5 @@ extern int _vfwprintf_internal (FILE * __restrict stream,
 #if defined(__STDIO_BUFFERS) || defined(__USE_OLD_VFPRINTF__) || defined(__UCLIBC_HAS_GLIBC_CUSTOM_STREAMS__)
 #define __STDIO_HAS_VSNPRINTF 1
 #endif
+
+#endif /* __STDIO_H_I */
diff --git a/libc/stdio/fclose.c b/libc/stdio/fclose.c
index 3417b2678..7e7bc3b5b 100644
--- a/libc/stdio/fclose.c
+++ b/libc/stdio/fclose.c
@@ -69,8 +69,6 @@ int fclose(register FILE *stream)
 	stream->__modeflags |= (__FLAG_READONLY|__FLAG_WRITEONLY);
 
 #ifndef NDEBUG
-	__STDIO_STREAM_RESET_GCS(stream);
-
 	/* Reinitialize everything (including putc since fflush could fail). */
 	__STDIO_STREAM_DISABLE_GETC(stream);
 	__STDIO_STREAM_DISABLE_PUTC(stream);
diff --git a/libc/stdio/fopencookie.c b/libc/stdio/fopencookie.c
index c4927e0bd..216dac39d 100644
--- a/libc/stdio/fopencookie.c
+++ b/libc/stdio/fopencookie.c
@@ -39,21 +39,34 @@ FILE *_fopencookie(void * __restrict cookie, const char * __restrict mode,
 #endif
 {
 	FILE *stream;
+	_IO_cookie_file_t *new_f;
 
+	new_f = malloc(sizeof(_IO_cookie_file_t));
+	if (new_f == NULL) {
+		return NULL;
+	}
+	new_f->__fp.__modeflags = __FLAG_FREEFILE;
+#ifdef __STDIO_BUFFERS
+	new_f->__fp.__bufstart = NULL; /* We allocate a buffer below. */
+#endif
+#ifdef __UCLIBC_HAS_THREADS__
+	/* We only initialize the mutex in the non-freopen case. */
+	STDIO_INIT_MUTEX(new_f->__fp.__lock);
+#endif
 	/* Fake an fdopen guaranteed to pass the _stdio_fopen basic agreement
 	 * check without an fcntl call. */
-	stream = _stdio_fopen(((intptr_t)(INT_MAX-1)), mode, NULL, INT_MAX);
+	stream = _stdio_fopen(((intptr_t)(INT_MAX-1)), mode, &new_f->__fp, INT_MAX);
 	if (stream) {
-		stream->__filedes = -1;
+		stream->__filedes = __STDIO_STREAM_GLIBC_CUSTOM_FILEDES;
 #ifndef __BCC__
-		stream->__gcs = io_functions;
+		new_f->__gcs = io_functions;
 #else
-		stream->__gcs.read  = io_functions->read;
-		stream->__gcs.write = io_functions->write;
-		stream->__gcs.seek  = io_functions->seek;
-		stream->__gcs.close = io_functions->close;
+		new_f->__gcs.read  = io_functions->read;
+		new_f->__gcs.write = io_functions->write;
+		new_f->__gcs.seek  = io_functions->seek;
+		new_f->__gcs.close = io_functions->close;
 #endif
-		stream->__cookie = cookie;
+		new_f->__cookie = cookie;
 
 		__STDIO_STREAM_VALIDATE(stream);
 	}
diff --git a/libc/stdio/fread.c b/libc/stdio/fread.c
index d2fcc70d5..5df33b468 100644
--- a/libc/stdio/fread.c
+++ b/libc/stdio/fread.c
@@ -15,7 +15,7 @@ size_t fread_unlocked(void * __restrict ptr, size_t size, size_t nmemb,
 						FILE * __restrict stream)
 {
 	__STDIO_STREAM_VALIDATE(stream);
-	assert(stream->__filedes >= -1);
+	assert(stream->__filedes >= -2);
 
 	/* Note: If nmbem * size > SIZE_MAX then there is an application
 	 * bug since no array can be larger than SIZE_MAX in size. */
diff --git a/libc/stdio/vdprintf.c b/libc/stdio/vdprintf.c
index 457018bcf..46b8dfe39 100644
--- a/libc/stdio/vdprintf.c
+++ b/libc/stdio/vdprintf.c
@@ -26,15 +26,6 @@ int vdprintf(int filedes, const char * __restrict format, va_list arg)
 	__STDIO_STREAM_INIT_BUFREAD_BUFPOS(&f);
 #endif
 
-/* 	__STDIO_STREAM_RESET_GCS(&f); */
-#ifdef __UCLIBC_HAS_GLIBC_CUSTOM_STREAMS__
-	f.__cookie = &(f.__filedes);
-	f.__gcs.read = NULL;
-	f.__gcs.write = _cs_write;
-	f.__gcs.seek = NULL;
-	f.__gcs.close = NULL;
-#endif
-
 	f.__filedes = filedes;
 	f.__modeflags = (__FLAG_NARROW|__FLAG_WRITEONLY|__FLAG_WRITING);
 
diff --git a/libc/stdio/vsnprintf.c b/libc/stdio/vsnprintf.c
index 31adc52b6..3a4c60794 100644
--- a/libc/stdio/vsnprintf.c
+++ b/libc/stdio/vsnprintf.c
@@ -22,15 +22,6 @@ int vsnprintf(char *__restrict buf, size_t size,
 	FILE f;
 	int rv;
 
-/* 	__STDIO_STREAM_RESET_GCS(&f); */
-#ifdef __UCLIBC_HAS_GLIBC_CUSTOM_STREAMS__
-	f.__cookie = &(f.__filedes);
-	f.__gcs.read = NULL;
-	f.__gcs.write = NULL;
-	f.__gcs.seek = NULL;
-	f.__gcs.close = NULL;
-#endif
-
 	f.__filedes = __STDIO_STREAM_FAKE_VSNPRINTF_FILEDES;
 	f.__modeflags = (__FLAG_NARROW|__FLAG_WRITEONLY|__FLAG_WRITING);
 
@@ -96,15 +87,6 @@ int vsnprintf(char *__restrict buf, size_t size,
 	}
 	f.bufend = buf + size;
 
-/* 	__STDIO_STREAM_RESET_GCS(&f.f); */
-#ifdef __UCLIBC_HAS_GLIBC_CUSTOM_STREAMS__
-	f.f.__cookie = &(f.f.__filedes);
-	f.f.__gcs.read = NULL;
-	f.f.__gcs.write = NULL;
-	f.f.__gcs.seek = NULL;
-	f.f.__gcs.close = NULL;
-#endif
-
 	f.f.__filedes = __STDIO_STREAM_FAKE_VSNPRINTF_FILEDES_NB;
 	f.f.__modeflags = (__FLAG_NARROW|__FLAG_WRITEONLY|__FLAG_WRITING);
 
@@ -137,7 +119,7 @@ libc_hidden_def(vsnprintf)
 typedef struct {
 	size_t pos;
 	size_t len;
-	unsigned char *buf;
+	char *buf;
 	FILE *fp;
 } __snpf_cookie;
 
@@ -175,34 +157,34 @@ static ssize_t snpf_write(register void *cookie, const char *buf,
 int vsnprintf(char *__restrict buf, size_t size,
 			  const char * __restrict format, va_list arg)
 {
-	FILE f;
+	_IO_cookie_file_t cf;
 	__snpf_cookie cookie;
 	int rv;
 
 	cookie.buf = buf;
 	cookie.len = size;
 	cookie.pos = 0;
-	cookie.fp = &f;
+	cookie.fp = &cf.__fp;
 
-	f.__cookie = &cookie;
-	f.__gcs.write = snpf_write;
-	f.__gcs.read = NULL;
-	f.__gcs.seek = NULL;
-	f.__gcs.close = NULL;
+	cf.__cookie = &cookie;
+	cf.__gcs.write = snpf_write;
+	cf.__gcs.read = NULL;
+	cf.__gcs.seek = NULL;
+	cf.__gcs.close = NULL;
 
-	f.__filedes = -1;			/* For debugging. */
-	f.__modeflags = (__FLAG_NARROW|__FLAG_WRITEONLY|__FLAG_WRITING);
+	cf.__fp.__filedes = __STDIO_STREAM_GLIBC_CUSTOM_FILEDES;
+	cf.__fp.__modeflags = (__FLAG_NARROW|__FLAG_WRITEONLY|__FLAG_WRITING);
 
 #ifdef __UCLIBC_HAS_WCHAR__
-	f.__ungot_width[0] = 0;
+	cf.__fp.__ungot_width[0] = 0;
 #endif /* __UCLIBC_HAS_WCHAR__ */
 #ifdef __STDIO_MBSTATE
-	__INIT_MBSTATE(&(f.__state));
+	__INIT_MBSTATE(&(cf.__fp.__state));
 #endif /* __STDIO_MBSTATE */
 
-	f.__nextopen = NULL;
+	cf.__fp.__nextopen = NULL;
 
-	rv = _vfprintf_internal(&f, format, arg);
+	rv = _vfprintf_internal(&cf.__fp, format, arg);
 
 	return rv;
 }
diff --git a/libc/stdio/vswprintf.c b/libc/stdio/vswprintf.c
index 219524830..58a06a763 100644
--- a/libc/stdio/vswprintf.c
+++ b/libc/stdio/vswprintf.c
@@ -22,15 +22,6 @@ int vswprintf(wchar_t *__restrict buf, size_t size,
 	FILE f;
 	int rv;
 
-/* 	__STDIO_STREAM_RESET_GCS(&f); */
-#ifdef __UCLIBC_HAS_GLIBC_CUSTOM_STREAMS__
-	f.__cookie = &(f.__filedes);
-	f.__gcs.read = NULL;
-	f.__gcs.write = NULL;
-	f.__gcs.seek = NULL;
-	f.__gcs.close = NULL;
-#endif
-
 	f.__filedes = __STDIO_STREAM_FAKE_VSWPRINTF_FILEDES;
 	f.__modeflags = (__FLAG_WIDE|__FLAG_WRITEONLY|__FLAG_WRITING);
 
diff --git a/libc/sysdeps/linux/common/bits/uClibc_stdio.h b/libc/sysdeps/linux/common/bits/uClibc_stdio.h
index 5b3a1b310..efd8a6c89 100644
--- a/libc/sysdeps/linux/common/bits/uClibc_stdio.h
+++ b/libc/sysdeps/linux/common/bits/uClibc_stdio.h
@@ -245,10 +245,6 @@ struct __STDIO_FILE_STRUCT {
 #ifdef __STDIO_HAS_OPENLIST
 	struct __STDIO_FILE_STRUCT *__nextopen;
 #endif
-#ifdef __UCLIBC_HAS_GLIBC_CUSTOM_STREAMS__
-	void *__cookie;
-	_IO_cookie_io_functions_t __gcs;
-#endif
 #ifdef __UCLIBC_HAS_WCHAR__
 	wchar_t __ungot[2];
 #endif
diff --git a/test/stdio/Makefile.in b/test/stdio/Makefile.in
index 0bfbd1362..14b5f19b9 100644
--- a/test/stdio/Makefile.in
+++ b/test/stdio/Makefile.in
@@ -2,3 +2,7 @@
 # Licensed under the LGPL v2.1, see the file COPYING.LIB in this tarball.
 
 DODIFF_64bit := 1
+
+ifeq ($(UCLIBC_HAS_GLIBC_CUSTOM_STREAMS),)
+TESTS_DISABLED += tst-fmemopen
+endif
diff --git a/test/stdio/tst-fmemopen.c b/test/stdio/tst-fmemopen.c
new file mode 100644
index 000000000..384faa1c9
--- /dev/null
+++ b/test/stdio/tst-fmemopen.c
@@ -0,0 +1,53 @@
+#include <string.h>
+#include <stdio.h>
+#include <stdlib.h>
+
+static char *text_input = "1 23 43";
+
+static const char *good_answer = "1 529 1849 ";
+
+
+static int
+do_test (void)
+{
+    FILE *out, *in;
+    int v, s;
+    size_t size;
+    char *ptr;
+
+    in = fmemopen(text_input, strlen(text_input), "r");
+    if (in == NULL) {
+        perror("fmemopen");
+	return 1;
+    }
+
+    out = open_memstream(&ptr, &size);
+    if (out == NULL) {
+        perror("open_memstream");
+	return 1;
+    }
+
+    for (;;) {
+        s = fscanf(in, "%d", &v);
+        if (s <= 0)
+            break;
+
+        s = fprintf(out, "%d ", v * v);
+        if (s == -1) {
+            puts("fprintf failed");
+	    exit(1);
+	}
+    }
+    fclose(in);
+    fclose(out);
+
+    if (size != strlen(good_answer) || strcmp(good_answer, ptr) != 0) {
+	printf("failed: size=%zu; ptr=%s\n", size, ptr);
+	exit(1);
+    }
+    free(ptr);
+    exit(0);
+}
+
+#define TEST_FUNCTION do_test ()
+#include "../test-skeleton.c"