refactor stdio open file list handling, move it out of global libc struct

functions which open in-memory FILE stream variants all shared a tail
with __fdopen, adding the FILE structure to stdio's open file list.
replacing this common tail with a function call reduces code size and
duplication of logic. the list is also partially encapsulated now.

function signatures were chosen to facilitate tail call optimization
and reduce the need for additional accessor functions.

with these changes, static linked programs that do not use stdio no
longer have an open file list at all.

src/stdio/__fdopen.c

@@ -54,13 +54,7 @@ FILE *__fdopen(int fd, const char *mode)
 	if (!libc.threaded) f->lock = -1;
 
 	/* Add new FILE to open file list */
-	OFLLOCK();
-	f->next = libc.ofl_head;
-	if (libc.ofl_head) libc.ofl_head->prev = f;
-	libc.ofl_head = f;
-	OFLUNLOCK();
-
-	return f;
+	return __ofl_add(f);
 }
 
 weak_alias(__fdopen, fdopen);

src/stdio/__stdio_exit.c

@@ -16,8 +16,7 @@ static void close_file(FILE *f)
 void __stdio_exit(void)
 {
 	FILE *f;
-	OFLLOCK();
-	for (f=libc.ofl_head; f; f=f->next) close_file(f);
+	for (f=*__ofl_lock(); f; f=f->next) close_file(f);
 	close_file(__stdin_used);
 	close_file(__stdout_used);
 }

src/stdio/fclose.c

@@ -14,11 +14,11 @@ int fclose(FILE *f)
 	__unlist_locked_file(f);
 
 	if (!(perm = f->flags & F_PERM)) {
-		OFLLOCK();
+		FILE **head = __ofl_lock();
 		if (f->prev) f->prev->next = f->next;
 		if (f->next) f->next->prev = f->prev;
-		if (libc.ofl_head == f) libc.ofl_head = f->next;
-		OFLUNLOCK();
+		if (*head == f) *head = f->next;
+		__ofl_unlock();
 	}
 
 	r = fflush(f);

src/stdio/fflush.c

@@ -35,13 +35,12 @@ int fflush(FILE *f)
 
 	r = __stdout_used ? fflush(__stdout_used) : 0;
 
-	OFLLOCK();
-	for (f=libc.ofl_head; f; f=f->next) {
+	for (f=*__ofl_lock(); f; f=f->next) {
 		FLOCK(f);
 		if (f->wpos > f->wbase) r |= __fflush_unlocked(f);
 		FUNLOCK(f);
 	}
-	OFLUNLOCK();
+	__ofl_unlock();
 	
 	return r;
 }

src/stdio/fmemopen.c

@@ -110,11 +110,5 @@ FILE *fmemopen(void *restrict buf, size_t size, const char *restrict mode)
 
 	if (!libc.threaded) f->lock = -1;
 
-	OFLLOCK();
-	f->next = libc.ofl_head;
-	if (libc.ofl_head) libc.ofl_head->prev = f;
-	libc.ofl_head = f;
-	OFLUNLOCK();
-
-	return f;
+	return __ofl_add(f);
 }

src/stdio/ofl.c

@@ -0,0 +1,16 @@
+#include "stdio_impl.h"
+#include "libc.h"
+
+static FILE *ofl_head;
+static volatile int ofl_lock[2];
+
+FILE **__ofl_lock()
+{
+	LOCK(ofl_lock);
+	return &ofl_head;
+}
+
+void __ofl_unlock()
+{
+	UNLOCK(ofl_lock);
+}

src/stdio/ofl_add.c

@@ -0,0 +1,11 @@
+#include "stdio_impl.h"
+
+FILE *__ofl_add(FILE *f)
+{
+	FILE **head = __ofl_lock();
+	f->next = *head;
+	if (*head) (*head)->prev = f;
+	*head = f;
+	__ofl_unlock();
+	return f;
+}

src/stdio/open_memstream.c

@@ -79,11 +79,5 @@ FILE *open_memstream(char **bufp, size_t *sizep)
 
 	if (!libc.threaded) f->lock = -1;
 
-	OFLLOCK();
-	f->next = libc.ofl_head;
-	if (libc.ofl_head) libc.ofl_head->prev = f;
-	libc.ofl_head = f;
-	OFLUNLOCK();
-
-	return f;
+	return __ofl_add(f);
 }

src/stdio/open_wmemstream.c

@@ -81,11 +81,5 @@ FILE *open_wmemstream(wchar_t **bufp, size_t *sizep)
 
 	if (!libc.threaded) f->lock = -1;
 
-	OFLLOCK();
-	f->next = libc.ofl_head;
-	if (libc.ofl_head) libc.ofl_head->prev = f;
-	libc.ofl_head = f;
-	OFLUNLOCK();
-
-	return f;
+	return __ofl_add(f);
 }