Add raw memory visualization tool to redbean

This change introduces a `-W /dev/pts/1` flag to redbean. What it does
is use the mincore() system call to create a dual-screen terminal
display that lets you troubleshoot the virtual address space. This is
useful since page faults are an important thing to consider when using a
forking web server. Now we have a colorful visualization of which pages
are going to fault and which ones are resident in memory.

The memory monitor, if enabled, spawns as a thread that just outputs
ANSI codes to the second terminal in a loop. In order to make this
happen using the new clone() polyfill, stdio is now thread safe.

This change also introduces some new demo pages to redbean. It also
polishes the demos we already have, to look a bit nicer and more
presentable for the upcoming release, with better explanations too.

libc/stdio/unlocked/clearerr_unlocked.S

@@ -18,11 +18,12 @@
 ╚─────────────────────────────────────────────────────────────────────────────*/
 #include "libc/macros.internal.h"
 
-clearerr_unlocked:
-	push	%rbp
-	mov	%rsp,%rbp
-	.profilable		# note: no consensus for threads exists in abis
-	call	clearerr
-	pop	%rbp
-	ret
-	.endfn	clearerr_unlocked,globl
+//	Clears error state on stream.
+//
+//	@param	rdi has stream pointer
+//	@see	clearerr_unlocked()
+clearerr:
+	mov	%rdi,%r11
+	ezlea	clearerr_unlocked,ax
+	jmp	stdio_unlock
+	.endfn	clearerr,globl

libc/stdio/unlocked/feof_unlocked.S

@@ -18,11 +18,12 @@
 ╚─────────────────────────────────────────────────────────────────────────────*/
 #include "libc/macros.internal.h"
 
-feof_unlocked:
-	push	%rbp
-	mov	%rsp,%rbp
-	.profilable		# note: no consensus for threads exists in abis
-	call	feof
-	pop	%rbp
-	ret
-	.endfn	feof_unlocked,globl
+//	Returns true if stream is in end-of-file state.
+//
+//	@param	rdi has file stream object pointer
+//	@note	EOF doesn't count
+//	@see	feof_unlocked()
+feof:	mov	%rdi,%r11
+	ezlea	feof_unlocked,ax
+	jmp	stdio_unlock
+	.endfn	feof,globl

libc/stdio/unlocked/ferror_unlocked.S

@@ -18,11 +18,12 @@
 ╚─────────────────────────────────────────────────────────────────────────────*/
 #include "libc/macros.internal.h"
 
-ferror_unlocked:
-	push	%rbp
-	mov	%rsp,%rbp
-	.profilable		# note: no consensus for threads exists in abis
-	call	ferror
-	pop	%rbp
-	ret
-	.endfn	ferror_unlocked,globl
+//	Returns nonzero if stream is in error state.
+//
+//	@param	rdi has file stream object pointer
+//	@note	EOF doesn't count
+//	@see	ferror_unlocked()
+ferror:	mov	%rdi,%r11
+	ezlea	ferror_unlocked,ax
+	jmp	stdio_unlock
+	.endfn	ferror,globl

libc/stdio/unlocked/fflush_unlocked.S

@@ -18,11 +18,12 @@
 ╚─────────────────────────────────────────────────────────────────────────────*/
 #include "libc/macros.internal.h"
 
-fflush_unlocked:
-	push	%rbp
-	mov	%rsp,%rbp
-	.profilable		# note: no consensus for threads exists in abis
-	call	fflush
-	pop	%rbp
-	ret
-	.endfn	fflush_unlocked,globl
+//	Blocks until data from stream buffer is written out.
+//
+//	@param	rdi is the stream handle
+//	@return	0 on success or -1 w/ errno
+//	@see	fflush_unlocked()
+fflush:	mov	%rdi,%r11
+	ezlea	fflush_unlocked,ax
+	jmp	stdio_unlock
+	.endfn	fflush,globl

libc/stdio/unlocked/fgetc_unlocked.S

@@ -18,11 +18,12 @@
 ╚─────────────────────────────────────────────────────────────────────────────*/
 #include "libc/macros.internal.h"
 
-fgetc_unlocked:
-	push	%rbp
-	mov	%rsp,%rbp
-	.profilable		# note: no consensus for threads exists in abis
-	call	fgetc
-	pop	%rbp
-	ret
-	.endfn	fgetc_unlocked,globl
+//	Reads byte from stream.
+//
+//	@param	rdi has stream object pointer
+//	@return byte in range 0..255, or -1 w/ errno
+//	@see	fgetc_unlocked()
+fgetc:	mov	%rdi,%r11
+	ezlea	fgetc_unlocked,ax
+	jmp	stdio_unlock
+	.endfn	fgetc,globl

libc/stdio/unlocked/fgets_unlocked.S

@@ -18,11 +18,19 @@
 ╚─────────────────────────────────────────────────────────────────────────────*/
 #include "libc/macros.internal.h"
 
-fgets_unlocked:
-	push	%rbp
-	mov	%rsp,%rbp
-	.profilable		# note: no consensus for threads exists in abis
-	call	fgets
-	pop	%rbp
-	ret
-	.endfn	fgets_unlocked,globl
+//	Reads line from stream.
+//
+//	This function is similar to getline() except it'll truncate
+//	lines exceeding size. The line ending marker is included
+//	and may be removed using _chomp().
+//
+//	@param	rdi is output buffer
+//	@param	rsi is size of rdi buffer
+//	@param	rdx is file stream object pointer
+//	@return	rax has rdi on success, NULL on error or
+//		NULL if EOF happens with zero chars read
+//	@see	fgets_unlocked()
+fgets:	mov	%rdx,%r11
+	ezlea	fgets_unlocked,ax
+	jmp	stdio_unlock
+	.endfn	fgets,globl

libc/stdio/unlocked/fgetwc_unlocked.S

@@ -18,11 +18,12 @@
 ╚─────────────────────────────────────────────────────────────────────────────*/
 #include "libc/macros.internal.h"
 
-fgetwc_unlocked:
-	push	%rbp
-	mov	%rsp,%rbp
-	.profilable		# note: no consensus for threads exists in abis
-	call	fgetwc
-	pop	%rbp
-	ret
-	.endfn	fgetwc_unlocked,globl
+//	Reads UTF-8 wide character from stream.
+//
+//	@param	rdi has stream object pointer
+//	@return wide character or -1 on EOF or error
+//	@see	fgetwc_unlocked()
+fgetwc:	mov	%rdi,%r11
+	ezlea	fgetwc_unlocked,ax
+	jmp	stdio_unlock
+	.endfn	fgetwc,globl

libc/stdio/unlocked/fgetws_unlocked.S

@@ -18,11 +18,17 @@
 ╚─────────────────────────────────────────────────────────────────────────────*/
 #include "libc/macros.internal.h"
 
-fgetws_unlocked:
-	push	%rbp
-	mov	%rsp,%rbp
-	.profilable		# note: no consensus for threads exists in abis
-	call	fgetws
-	pop	%rbp
-	ret
-	.endfn	fgetws_unlocked,globl
+//	Reads UTF-8 content from stream into UTF-32 buffer.
+//
+//	This function is similar to getline() except it'll truncate lines
+//	exceeding size. The line ending marker is included and may be removed
+//	using _chomp().
+//
+//	@param	rdi is nul-terminated string that's non-null
+//	@param	rsi is size of rdi buffer
+//	@param	rsi is file stream object pointer
+//	@see	fgetws_unlocked()
+fgetws:	mov	%rdx,%r11
+	ezlea	fgetws_unlocked,ax
+	jmp	stdio_unlock
+	.endfn	fgetws,globl

libc/stdio/unlocked/fileno_unlocked.S

@@ -18,11 +18,11 @@
 ╚─────────────────────────────────────────────────────────────────────────────*/
 #include "libc/macros.internal.h"
 
-fileno_unlocked:
-	push	%rbp
-	mov	%rsp,%rbp
-	.profilable		# note: no consensus for threads exists in abis
-	call	fileno
-	pop	%rbp
-	ret
-	.endfn	fileno_unlocked,globl
+//	Returns file descriptor associated with stream.
+//
+//	@param	rdi has file stream object pointer
+//	@see	fileno_unlocked()
+fileno:	mov	%rdi,%r11
+	ezlea	fileno_unlocked,ax
+	jmp	stdio_unlock
+	.endfn	fileno,globl

libc/stdio/unlocked/fputc_unlocked.S

@@ -18,11 +18,13 @@
 ╚─────────────────────────────────────────────────────────────────────────────*/
 #include "libc/macros.internal.h"
 
-fputc_unlocked:
-	push	%rbp
-	mov	%rsp,%rbp
-	.profilable		# note: no consensus for threads exists in abis
-	call	fputc
-	pop	%rbp
-	ret
-	.endfn	fputc_unlocked,globl
+//	Writes character to stream.
+//
+//	@param	rdi c is byte to buffer or write, which is masked
+//	@param	rsi has stream object pointer
+//	@return c as unsigned char if written or -1 w/ errno
+//	@see	fputc_unlocked()
+fputc:	mov	%rsi,%r11
+	ezlea	fputc_unlocked,ax
+	jmp	stdio_unlock
+	.endfn	fputc,globl

libc/stdio/unlocked/fputs_unlocked.S

@@ -18,11 +18,17 @@
 ╚─────────────────────────────────────────────────────────────────────────────*/
 #include "libc/macros.internal.h"
 
-fputs_unlocked:
-	push	%rbp
-	mov	%rsp,%rbp
-	.profilable		# note: no consensus for threads exists in abis
-	call	fputs
-	pop	%rbp
-	ret
-	.endfn	fputs_unlocked,globl
+//	Writes string to stream.
+//
+//	Writing stops at the NUL-terminator, which isn't included in output.
+//	This function blocks until the full string is written, unless an
+//	unrecoverable error happens.
+//
+//	@param	rdi is nul-terminated string that's non-null
+//	@param	rsi is file object stream pointer
+//	@return	strlen(rdi) on success or -1 w/ errno
+//	@see	fputs_unlocked()
+fputs:	mov	%rsi,%r11
+	ezlea	fputs_unlocked,ax
+	jmp	stdio_unlock
+	.endfn	fputs,globl

libc/stdio/unlocked/fputwc_unlocked.S

@@ -18,11 +18,13 @@
 ╚─────────────────────────────────────────────────────────────────────────────*/
 #include "libc/macros.internal.h"
 
-fputwc_unlocked:
-	push	%rbp
-	mov	%rsp,%rbp
-	.profilable		# note: no consensus for threads exists in abis
-	call	fputwc
-	pop	%rbp
-	ret
-	.endfn	fputwc_unlocked,globl
+//	Writes wide character to stream.
+//
+//	@param	rdi has wide character
+//	@param	rsi has file object stream pointer
+//	@return	rax is wide character if written or -1 w/ errno
+//	@see	fputwc_unlocked()
+fputwc:	mov	%rsi,%r11
+	ezlea	fputwc_unlocked,ax
+	jmp	stdio_unlock
+	.endfn	fputwc,globl

libc/stdio/unlocked/fputws_unlocked.S

@@ -18,11 +18,17 @@
 ╚─────────────────────────────────────────────────────────────────────────────*/
 #include "libc/macros.internal.h"
 
-fputws_unlocked:
-	push	%rbp
-	mov	%rsp,%rbp
-	.profilable		# note: no consensus for threads exists in abis
-	call	fputws
-	pop	%rbp
-	ret
-	.endfn	fputws_unlocked,globl
+//	Writes wide character string to stream.
+//
+//	Writing stops at the NUL-terminator, which isn't included in output.
+//	This function blocks until the full string is written, unless an
+//	unrecoverable error happens.
+//
+//	@param	rdi is nul-terminated string that's non-null
+//	@param	rsi is file object stream pointer
+//	@return	strlen(rdi) on success or -1 w/ errno
+//	@see	fputws_unlocked()
+fputws:	mov	%rsi,%r11
+	ezlea	fputws_unlocked,ax
+	jmp	stdio_unlock
+	.endfn	fputws,globl

libc/stdio/unlocked/fread_unlocked.S

@@ -18,11 +18,15 @@
 ╚─────────────────────────────────────────────────────────────────────────────*/
 #include "libc/macros.internal.h"
 
-fread_unlocked:
-	push	%rbp
-	mov	%rsp,%rbp
-	.profilable		# note: no consensus for threads exists in abis
-	call	fread
-	pop	%rbp
-	ret
-	.endfn	fread_unlocked,globl
+//	Reads data from stream.
+//
+//	@param	rdi has pointer to data to read
+//	@param	rsi stride specifies the size of individual items
+//	@param	rdx count is the number of strides to read
+//	@param	rcx has file object stream pointer
+//	@return	count on success, [0,count) on EOF, 0 on error or count==0
+//	@see	fread_unlocked()
+fread:	mov	%rcx,%r11
+	ezlea	fread_unlocked,ax
+	jmp	stdio_unlock
+	.endfn	fread,globl

libc/stdio/unlocked/fwrite_unlocked.S

@@ -18,11 +18,15 @@
 ╚─────────────────────────────────────────────────────────────────────────────*/
 #include "libc/macros.internal.h"
 
-fwrite_unlocked:
-	push	%rbp
-	mov	%rsp,%rbp
-	.profilable		# note: no consensus for threads exists in abis
-	call	fwrite
-	pop	%rbp
-	ret
-	.endfn	fwrite_unlocked,globl
+//	Writes data to stream.
+//
+//	@param	rdi has pointer to data to write
+//	@param	rsi stride specifies the size of individual items
+//	@param	rdx count is the number of strides to write
+//	@param	rcx has file object stream pointer
+//	@return	count on success, [0,count) on EOF, 0 on error or count==0
+//	@see	fwrite_unlocked()
+fwrite:	mov	%rcx,%r11
+	ezlea	fwrite_unlocked,ax
+	jmp	stdio_unlock
+	.endfn	fwrite,globl

libc/stdio/unlocked/getc_unlocked.S

@@ -18,11 +18,12 @@
 ╚─────────────────────────────────────────────────────────────────────────────*/
 #include "libc/macros.internal.h"
 
-getc_unlocked:
-	push	%rbp
-	mov	%rsp,%rbp
-	.profilable		# note: no consensus for threads exists in abis
-	call	getc
-	pop	%rbp
-	ret
-	.endfn	getc_unlocked,globl
+//	Reads character from stream.
+//
+//	@param	rdi has file stream object pointer
+//	@return	byte in range 0..255, or -1 w/ errno
+//	@see	fgetc_unlocked()
+getc:	mov	%rdi,%r11
+	ezlea	fgetwc_unlocked,ax
+	jmp	stdio_unlock
+	.endfn	getc,globl

libc/stdio/unlocked/getchar_unlocked.S

@@ -18,11 +18,13 @@
 ╚─────────────────────────────────────────────────────────────────────────────*/
 #include "libc/macros.internal.h"
 
-getchar_unlocked:
-	push	%rbp
-	mov	%rsp,%rbp
-	.profilable		# note: no consensus for threads exists in abis
-	call	getchar
-	pop	%rbp
-	ret
-	.endfn	getchar_unlocked,globl
+//	Reads character from stdin.
+//
+//	@return	byte in range 0..255, or -1 w/ errno
+//	@see	fgetc_unlocked()
+getchar:
+	lea	stdin(%rip),%rdi
+	mov	%rdi,%r11
+	ezlea	fgetc_unlocked,ax
+	jmp	stdio_unlock
+	.endfn	getchar,globl

libc/stdio/unlocked/getwc_unlocked.S

@@ -18,11 +18,12 @@
 ╚─────────────────────────────────────────────────────────────────────────────*/
 #include "libc/macros.internal.h"
 
-getwc_unlocked:
-	push	%rbp
-	mov	%rsp,%rbp
-	.profilable		# note: no consensus for threads exists in abis
-	call	fgetwc_unlocked
-	pop	%rbp
-	ret
-	.endfn	getwc_unlocked,globl
+//	Reads UTF-8 character from stream.
+//
+//	@param	rdi has file stream object pointer
+//	@return	wide character or -1 on EOF or error
+//	@see	fgetwc_unlocked()
+getwc:	mov	%rdi,%r11
+	ezlea	fgetwc_unlocked,ax
+	jmp	stdio_unlock
+	.endfn	getwc,globl

libc/stdio/unlocked/getwchar_unlocked.S

@@ -18,11 +18,13 @@
 ╚─────────────────────────────────────────────────────────────────────────────*/
 #include "libc/macros.internal.h"
 
-getwchar_unlocked:
-	push	%rbp
-	mov	%rsp,%rbp
-	.profilable		# note: no consensus for threads exists in abis
-	call	getwchar
-	pop	%rbp
-	ret
-	.endfn	getwchar_unlocked,globl
+//	Reads UTF-8 character from stdin.
+//
+//	@return	wide character or -1 on EOF or error
+//	@see	fgetwc_unlocked()
+getwchar:
+	lea	stdin(%rip),%rdi
+	mov	%rdi,%r11
+	ezlea	fgetwc_unlocked,ax
+	jmp	stdio_unlock
+	.endfn	getwchar,globl

libc/stdio/unlocked/putc_unlocked.S

@@ -18,11 +18,13 @@
 ╚─────────────────────────────────────────────────────────────────────────────*/
 #include "libc/macros.internal.h"
 
-putc_unlocked:
-	push	%rbp
-	mov	%rsp,%rbp
-	.profilable		# note: no consensus for threads exists in abis
-	call	putc
-	pop	%rbp
-	ret
-	.endfn	putc_unlocked,globl
+//	Writes character to stream.
+//
+//	@param	rdi c is byte to buffer or write, which is masked
+//	@param	rsi has stream object pointer
+//	@return c as unsigned char if written or -1 w/ errno
+//	@see	fputc_unlocked()
+putc:	mov	%rsi,%r11
+	ezlea	fputc_unlocked,ax
+	jmp	stdio_unlock
+	.endfn	putc,globl

libc/stdio/unlocked/putchar_unlocked.S

@@ -18,11 +18,14 @@
 ╚─────────────────────────────────────────────────────────────────────────────*/
 #include "libc/macros.internal.h"
 
-putchar_unlocked:
-	push	%rbp
-	mov	%rsp,%rbp
-	.profilable		# note: no consensus for threads exists in abis
-	call	putchar
-	pop	%rbp
-	ret
-	.endfn	putchar_unlocked,globl
+//	Writes character to stdout.
+//
+//	@param	rdi has character
+//	@return c (as unsigned char) if written or -1 w/ errno
+//	@see	fputc_unlocked()
+putchar:
+	lea	stdout(%rip),%rsi
+	mov	%rsi,%r11
+	ezlea	fputc_unlocked,ax
+	jmp	stdio_unlock
+	.endfn	putchar,globl

libc/stdio/unlocked/putwc_unlocked.S

@@ -18,11 +18,13 @@
 ╚─────────────────────────────────────────────────────────────────────────────*/
 #include "libc/macros.internal.h"
 
-putwc_unlocked:
-	push	%rbp
-	mov	%rsp,%rbp
-	.profilable		# note: no consensus for threads exists in abis
-	call	fputwc_unlocked
-	pop	%rbp
-	ret
-	.endfn	putwc_unlocked,globl
+//	Writes wide character to stream.
+//
+//	@param	rdi has wide character
+//	@param	rsi has file object
+//	@return wc if written or -1 w/ errno
+//	@see	putwc_unlocked()
+putwc:	mov	%rsi,%r11
+	ezlea	fputwc_unlocked,ax
+	jmp	stdio_unlock
+	.endfn	putwc,globl

libc/stdio/unlocked/putwchar_unlocked.S

@@ -1,4 +1,3 @@
-
 /*-*- mode:unix-assembly; indent-tabs-mode:t; tab-width:8; coding:utf-8     -*-│
 │vi: set et ft=asm ts=8 tw=8 fenc=utf-8                                     :vi│
 ╞══════════════════════════════════════════════════════════════════════════════╡
@@ -19,11 +18,14 @@
 ╚─────────────────────────────────────────────────────────────────────────────*/
 #include "libc/macros.internal.h"
 
-putwchar_unlocked:
-	push	%rbp
-	mov	%rsp,%rbp
-	.profilable		# note: no consensus for threads exists in abis
-	call	putwchar
-	pop	%rbp
-	ret
-	.endfn	putwchar_unlocked,globl
+//	Writes wide character to stdout.
+//
+//	@param	rdi has wide character
+//	@return wc if written or -1 w/ errno
+//	@see	fputwc_unlocked()
+putwchar:
+	lea	stdout(%rip),%rsi
+	mov	%rsi,%r11
+	ezlea	fputwc_unlocked,ax
+	jmp	stdio_unlock
+	.endfn	putwchar,globl

libc/stdio/unlocked/stdio_unlock.S

@@ -0,0 +1,70 @@
+/*-*- mode:unix-assembly; indent-tabs-mode:t; tab-width:8; coding:utf-8     -*-│
+│vi: set et ft=asm ts=8 tw=8 fenc=utf-8                                     :vi│
+╞══════════════════════════════════════════════════════════════════════════════╡
+│ Copyright 2022 Justine Alexandra Roberts Tunney                              │
+│                                                                              │
+│ Permission to use, copy, modify, and/or distribute this software for         │
+│ any purpose with or without fee is hereby granted, provided that the         │
+│ above copyright notice and this permission notice appear in all copies.      │
+│                                                                              │
+│ THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL                │
+│ WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED                │
+│ WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE             │
+│ AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL         │
+│ DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR        │
+│ PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER               │
+│ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR             │
+│ PERFORMANCE OF THIS SOFTWARE.                                                │
+╚─────────────────────────────────────────────────────────────────────────────*/
+#include "libc/macros.internal.h"
+
+#define LOCK 0x2c /* see struct file in stdio.h */
+
+//	Wrapper for applying locking to stdio functions.
+//
+//	This function is intended to be called by thunks.
+//
+//	@param	rax has the delegate function pointer
+//	@param	rdi is passed along as an arg
+//	@param	rsi is passed along as an arg
+//	@param	rdx is passed along as an arg
+//	@param	rcx is passed along as an arg
+//	@param	r8  is passed along as an arg
+//	@param	r9  is passed along as an arg
+//	@param	r10 is passed along as an arg
+//	@param	r11 has the FILE* obj pointer
+//	@return	rax is passed along as result
+//	@return	rdx is passed along as result
+stdio_unlock:
+	push	%rbp
+	mov	%rsp,%rbp
+
+//	acquires mutex
+	push	%rcx
+	push	%rdx
+	mov	$1,%cl
+0:	mov	LOCK(%r11),%dl			# optimistic
+	test	%dl,%dl
+	je	2f
+1:	pause					# hyperyield
+	jmp	0b
+2:	mov	%ecx,%edx
+	xchg	LOCK(%r11),%dl			# locks bus!
+	test	%dl,%dl
+	jne	1b
+	pop	%rdx
+	pop	%rcx
+
+//	calls delegate
+	push	%rsi
+	push	%r11
+	call	*%rax
+	pop	%r11
+	pop	%rsi
+
+//	releases mutex
+	movb	$0,LOCK(%r11)
+
+	pop	%rbp
+	ret
+	.endfn	stdio_unlock,globl

libc/stdio/unlocked/ungetc_unlocked.S

@@ -0,0 +1,30 @@
+/*-*- mode:unix-assembly; indent-tabs-mode:t; tab-width:8; coding:utf-8     -*-│
+│vi: set et ft=asm ts=8 tw=8 fenc=utf-8                                     :vi│
+╞══════════════════════════════════════════════════════════════════════════════╡
+│ Copyright 2022 Justine Alexandra Roberts Tunney                              │
+│                                                                              │
+│ Permission to use, copy, modify, and/or distribute this software for         │
+│ any purpose with or without fee is hereby granted, provided that the         │
+│ above copyright notice and this permission notice appear in all copies.      │
+│                                                                              │
+│ THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL                │
+│ WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED                │
+│ WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE             │
+│ AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL         │
+│ DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR        │
+│ PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER               │
+│ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR             │
+│ PERFORMANCE OF THIS SOFTWARE.                                                │
+╚─────────────────────────────────────────────────────────────────────────────*/
+#include "libc/macros.internal.h"
+
+//	Pushes byte back to stream.
+//
+//	@param	rdi has character to push
+//	@param	rds has stream object pointer
+//	@return rax has rdi on success or -1 w/ errno
+//	@see	ungetc_unlocked()
+ungetc:	mov	%rsi,%r11
+	ezlea	ungetc_unlocked,ax
+	jmp	stdio_unlock
+	.endfn	ungetc,globl

libc/stdio/unlocked/ungetwc_unlocked.S

@@ -0,0 +1,31 @@
+/*-*- mode:unix-assembly; indent-tabs-mode:t; tab-width:8; coding:utf-8     -*-│
+│vi: set et ft=asm ts=8 tw=8 fenc=utf-8                                     :vi│
+╞══════════════════════════════════════════════════════════════════════════════╡
+│ Copyright 2022 Justine Alexandra Roberts Tunney                              │
+│                                                                              │
+│ Permission to use, copy, modify, and/or distribute this software for         │
+│ any purpose with or without fee is hereby granted, provided that the         │
+│ above copyright notice and this permission notice appear in all copies.      │
+│                                                                              │
+│ THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL                │
+│ WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED                │
+│ WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE             │
+│ AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL         │
+│ DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR        │
+│ PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER               │
+│ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR             │
+│ PERFORMANCE OF THIS SOFTWARE.                                                │
+╚─────────────────────────────────────────────────────────────────────────────*/
+#include "libc/macros.internal.h"
+
+//	Pushes byte back to stream.
+//
+//	@param	rdi has character to push
+//	@param	rds has stream object pointer
+//	@return rax has rdi on success or -1 w/ errno
+//	@see	ungetwc_unlocked()
+ungetwc:
+	mov	%rsi,%r11
+	ezlea	ungetwc_unlocked,ax
+	jmp	stdio_unlock
+	.endfn	ungetwc,globl