LibC: Fix memchr and memcmp assembly implementations

These functions did not work with size 0 :D
2025-01-23 21:55:26 +02:00
parent ee078fc638
commit 15021b442c
2 changed files with 10 additions and 6 deletions
--- a/userspace/libraries/LibC/arch/x86_64/string.S
+++ b/userspace/libraries/LibC/arch/x86_64/string.S
@@ -2,15 +2,17 @@
 memchr:
 	movb %sil, %al
 	movq %rdx, %rcx
+	movq $1, %rdx
+	cmpq $1, %rcx # clear ZF if count is zero
 	repne scasb
-	xorq %rax, %rax
-	testq %rcx, %rcx
-	cmovnzq %rdi, %rax
+	cmoveq %rdi, %rdx
+	leaq -1(%rdx), %rax
 	ret

 .global memcmp
 memcmp:
 	movq %rdx, %rcx
+	testq %rcx, %rcx # set ZF if count is zero
 	repe cmpsb
 	jne .memcmp_not_equal
 	xorq %rax, %rax