fixed behavior of memset((void*)-1, ch, 0) along with bzero and wmemset

Author: ZERICO2005

src/libc/bzero.src

@@ -14,8 +14,8 @@ _bzero:
 	add	hl, sp
 	ld	bc, (hl)	; size
 	inc	bc
-	cpd	; dec hl
-	ret	po	; zero size
+	cpd			; dec hl
+	ret	po		; zero size
 	dec	hl
 	dec	hl
 	ld	de, (hl)	; buf
@@ -31,20 +31,21 @@ else
 _bzero:
 	ld	hl, 6
 	add	hl, sp
-	ld	bc, (hl)
+	ld	bc, (hl)	; BC = size
 	dec	hl
 	dec	hl
 	dec	hl
-	ld	hl, (hl)
-	cpi
-	add	hl, bc
-	ret	c
-	dec	hl
+	ld	de, (hl)	; DE = dst
+	scf
+	sbc	hl, hl
+	add	hl, bc		; HL = size - 1
+	ret	nc		; size == 0
+	add	hl, de		; HL = dst + size - 1
 	ld	(hl), 0
-	ret	po
-	push	hl
-	pop	de
-	dec	de
+	cpd			; HL = dst + size - 2, BC = size - 1
+	ex	de, hl		; DE = dst + size - 2, HL = dst
+	ret	po		; return if size == 1
+	add	hl, bc		; HL = dst + size - 1
 	lddr
 	ret
 

src/libc/memset.src

@@ -5,19 +5,20 @@
 	public	_memset
 
 _memset:
-	ld	iy, 0
+	ld	iy, -1
 	add	iy, sp
-	ld	hl, (iy + 3)
-	ld	bc, (iy + 9)
-	cpi
-	add	hl, bc
-	ret	c
-	dec	hl
-	ld	e, (iy + 6)
-	ld	(hl), e
-	ret	po
-	push	hl
-	pop	de
-	dec	de
+	ld	bc, (iy + 10)	; BC = size
+	sbc	hl, hl		; always resets overflow
+	add	hl, bc		; HL = size - 1
+	ld	de, (iy + 4)	; DE = dst
+	jr	nc, .zero_size
+	ld	a, (iy + 7)
+	add	hl, de		; HL = dst + size - 1
+	ld	(hl), a
+	cpd			; HL = dst + size - 2, BC = size - 1
+.zero_size:
+	ex	de, hl		; DE = dst + size - 2, HL = dst
+	ret	po		; return if size == 1
+	add	hl, bc		; HL = dst + size - 1
 	lddr
 	ret

src/libc/wmemset.src

@@ -6,33 +6,30 @@
 
 ; wchar_t *wmemset(wchar_t *dst, wchar_t ch, size_t count)
 _wmemset:
-	pop	iy, hl, de, bc
-	push	bc, de, hl, iy
-	; BC = count
-	; DE = ch
-	; HL = dst
-
-	; count *= sizeof(wchar_t)
-	cpi			; hl++ bc--
-	add	hl, bc		; HL = (dst + 1) + (count - 1) = dst + count
-	ret	c		; bc is zero
-	add	hl, bc		; HL = dst + count + (count - 1) = dst + 2 * count - 1
-
-	; hl += (count - 1) * 2 + 1
-	; count -= 2
-	ld	(hl), d		; upper 8 bits
-	dec	hl
-	ld	(hl), e		; lower 8 bits
-	ret	po		; only one element needs to be written
-
-	; write multiple elements
-	push	hl
-	pop	de
-	inc	hl
-	dec	de
-
-	push	bc
+	ld	iy, -1
+	add	iy, sp
+	ld	bc, (iy + 10)	; BC = count
+	sbc	hl, hl
+	add	hl, bc		; HL = count - 1
+	ex	de, hl		; DE = count - 1
+	ld	hl, (iy + 4)	; HL = dst
+	ret	nc		; count == 0
+	add	hl, bc		; HL = dst + count
+	add	hl, de		; HL = dst + 2 * count - 1
+	ex	de, hl		; DE = dst + 2 * count - 1
+	lea	hl, iy + 8	; HL = &upper_byte
+	ldd
+	; HL = &lower_byte
+	; DE = dst + 2 * count - 2
+	ld	a, (hl)
+	ld	(de), a
+	push	de
+	pop	hl
+	ret	po		; count == 1
+	inc	hl		; HL = dst + 2 * count - 1
+	dec	de		; DE = dst + 2 * count - 3
 	; use lddr twice
+	push	bc
 	lddr
 	pop	bc
 	lddr

test/standalone/asprintf_fprintf/src/main.c

@@ -521,6 +521,15 @@ int mempcpy_test(void) {
 int bzero_test(void) {
     char truth[32];
     char data[32];
+
+    // test zero size cases
+    C(T_memset(NULL_ptr, 0xCE, 0) == NULL_ptr);
+    C(T_memset((void*)0xFFFFFF, 0xCE, 0) == (void*)0xFFFFFF);
+    C(T_memset((void*)0x000001, 0xCE, 0) == (void*)0x000001);
+    T_bzero(NULL_ptr, 0);
+    T_bzero((void*)0xFFFFFF, 0);
+    T_bzero((void*)0x000001, 0);
+
     T_memset(data, 0x8F, sizeof(data));
     T_memset(&truth[ 0], 0x8F,  8);
     T_memset(&truth[ 2], 0x00,  1);

test/standalone/wide_char/src/main.c

@@ -24,7 +24,7 @@
 extern wchar_t * const PTR_000000;
 extern wchar_t * const PTR_FFFFFF;
 
-#if 0
+#if 1
 
 int       T_wmemcmp(const wchar_t *s1, const wchar_t *s2, size_t n) __NOEXCEPT __attribute__((__pure__));
 wchar_t * T_wmemchr(const wchar_t *ptr, int ch, size_t count) __NOEXCEPT __attribute__((__pure__));
@@ -182,6 +182,10 @@ int test_wmemset(void) {
         test_printf("%p != %p\n", ptr, (void*)0xC0FFEE);
         return __LINE__;
     }
+    C(wmemset(PTR_000000, 0x71CE, 0) == PTR_000000);
+    C(wmemset(PTR_FFFFFF, 0x71CE, 0) == PTR_FFFFFF);
+    C(wmemset((void*)0x000001, 0x71CE, 0) == (void*)0x000001);
+
     wchar_t data[192 + 1];
     memset(data, 0xBC, sizeof(data));
     wmemset(wmemset(&data[  0], 0x0012, 64) + 64, 0x0012, 64);
@@ -194,7 +198,7 @@ int test_wmemset(void) {
         test_printf("%p != %p\n", res, &data[64]);
         return __LINE__;
     }
-    
+
     wchar_t truth[192 + 1];
     memset(truth, 0xDE, sizeof(truth));
     C(&truth[  0] == wmemset(&truth[  0], 0x0012, 64));
@@ -230,7 +234,7 @@ int test_wmemset(void) {
 int test_wmemmove(void) {
     wchar_t move_str[] =
     {0x000F, 0x111F, 0x222F, 0x333F, 0x444F, 0x555F, 0x666F, 0x777F, 0x888F, 0x999F};
-    const wchar_t truth_str[] = 
+    const wchar_t truth_str[] =
     {0x999F, 0x333F, 0x444F, 0x444F, 0x555F, 0x444F, 0x555F, 0x666F, 0x888F, 0x999F};
     C(move_str + 5 == wmemmove(move_str + 5, move_str + 4, 3));
     C(move_str + 3 == wmemmove(move_str + 3, move_str + 3, 0));

test/standalone/wide_char/src/rename.asm

@@ -9,3 +9,20 @@ _PTR_000000:
 	public	_PTR_FFFFFF
 _PTR_FFFFFF:
 	db	$FF, $FF, $FF
+
+	section	.text
+
+	public	_T_wmemset, _T_wmemcpy, _T_wmemmove, _T_wmemcmp, _T_wmemchr
+	public	_T_wcslen, _T_wcsnlen
+
+_T_wmemset := _wmemset
+_T_wmemcpy := _wmemcpy
+_T_wmemmove := _wmemmove
+_T_wmemcmp := _wmemcmp
+_T_wmemchr := _wmemchr
+
+_T_wcslen := _wcslen
+_T_wcsnlen := _wcsnlen
+
+	extern	_wmemset, _wmemcpy, _wmemmove, _wmemcmp, _wmemchr
+	extern	_wcslen, _wcsnlen