From 9d265e3db6856bfb4024eb0f359d6cc35a910b17 Mon Sep 17 00:00:00 2001
From: Kwarde <kevin@kwarde.com>
Date: Wed, 25 Jun 2025 08:35:25 +0200
Subject: [PATCH] Fix strcmp()

---
 string.asm | 37 +++++++++++++++++++------------------
 tests.asm  | 35 ++++++++++++++++++++++++++++-------
 2 files changed, 47 insertions(+), 25 deletions(-)

diff --git a/string.asm b/string.asm
index 41ae21f..decfd05 100644
--- a/string.asm
+++ b/string.asm
@@ -96,32 +96,33 @@ strcat:
 	leave
 	ret
 ;----- strcmp(char* str1, char* str2) -----;
-; return value: 0 if both strings are the same, otherwise index in array str1 where strings are to become different
+; return value: 0 if both strings are the same, otherwise index in array str1 where strings mismatch
 ; returns -1 if str2 is longer than str1 and no difference was found before that happens
-; TODO: FIX length 13 for TEST strcmp(strBuff1, str1) (see tests.asm, strcmp test 1)
 strcmp:
 	push	rbp
 	mov	rbp, rsp
 
 	call	strlen
-	mov	rcx, rax
-	mov	rax, -1
+	xor	r10, r10
 	.compareLoop:
-		inc	rax
-		cmp	byte [rdi+rax], 0x0
-		je	.eosFound
-		mov	r10b, byte [rsi+rax]
-		cmp	byte [rdi+rax], r10b
-		je	.compareLoop
-	jmp	.quit
+		cmp	byte [rdi], 0x0
+		je	.0f
+		mov	r11b, byte [rsi]
+		cmp	byte [rdi], r11b
+		jne	.mismatch
+		inc	rdi
+		inc	rsi
+		inc	r10
+		jmp	.compareLoop
+	.0f:
+		mov	rax, -1
+		cmp	byte [rsi], 0x0
+		jne	.quit
+		xor	rax, rax
+		jmp	.quit
 
-	.eosFound:
-	mov	r10, rax
-	mov	rdi, rsi
-	call	strlen
-	cmp	rax, r10
-	jle	.quit
-	mov	rax, -1
+	.mismatch:
+		mov	rax, r10
 
 	.quit:
 	leave
diff --git a/tests.asm b/tests.asm
index 4ceca5a..f4c3778 100644
--- a/tests.asm
+++ b/tests.asm
@@ -133,12 +133,14 @@ section	.rodata
 	msgToupper1	db	"TEST toupper(strBuff1[0]): %c",NL,EOS
 	msgToupper2	db	"TEST toupper for whole strBuff1: %s",NL,EOS
 	; strcmp()
-	msgStrcmp	db	NL,"# strcmp()",NL,"strlclr(strBuff1, 32)",NL,"strcpy(strBuff1, str1)",EOS
+	msgStrcmp	db	NL,"# strcmp()",NL,"strlclr(strBuff1, 32)",NL,"strcpy(strBuff1, str1)",NL,"toupper(strBuff1[7])",EOS
 	msgStrcmpStrs	db	"> str1: %s",NL,"> str2: %s",NL,"> str4: %s",NL,"> strBuff1: %s",NL,EOS
 	msgStrcmp1	db	"TEST strcmp(strBuff1, str1): %d",NL,EOS
-	msgStrcmp2	db	"TEST strcmp(strBuff1, str2): %d",NL,EOS
-	msgStrcmp3	db	"TEST strcmp(str4, str1): %d",NL,EOS
-	msgStrcmp4	db	"TEST strcmp(str1, str4): %d",NL,EOS
+	msgStrcmp2	db	"TEST strcmp(str1, str2): %d",NL,EOS
+	msgStrcmp3	db	"TEST strcmp(strBuff1, str2): %d",NL,EOS
+	msgStrcmp4	db	"TEST strcmp(str4, str1): %d",NL,EOS
+	msgStrcmp5	db	"TEST strcmp(str1, str4): %d",NL,EOS
+	msgStrcmp6	db	"TEST strcmp(str1, str1): %d",NL,EOS
 section .bss
 	strBuff1	resb	32
 	strBuff2	resb	8
@@ -649,6 +651,9 @@ main:
 	lea	rdi, [rel strBuff1]
 	lea	rsi, [rel str1]
 	call	strcpy
+	lea	rdi, [rel strBuff1+7]
+	call	toupper
+	mov	[strBuff1+7], al
 
 	xor	rax, rax
 	lea	rdi, [rel msgStrcmpStrs]
@@ -666,13 +671,21 @@ main:
 	xor	rax, rax
 	lea	rdi, [rel msgStrcmp1]
 	call	printf
+	; TEST: strcmp(str1, str2)
+	lea	rdi, [rel str1]
+	lea	rsi, [rel str2]
+	call	strcmp
+	mov	rsi, rax
+	xor	rax, rax
+	lea	rdi, [rel msgStrcmp2]
+	call	printf
 	; TEST: strcmp(strBuff1, str2)
 	lea	rdi, [rel strBuff1]
 	lea	rsi, [rel str2]
 	call	strcmp
 	mov	rsi, rax
 	xor	rax, rax
-	lea	rdi, [rel msgStrcmp2]
+	lea	rdi, [rel msgStrcmp3]
 	call	printf
 	; TEST: strcmp(str4, str1)
 	lea	rdi, [rel str4]
@@ -680,7 +693,7 @@ main:
 	call	strcmp
 	mov	rsi, rax
 	xor	rax, rax
-	lea	rdi, [rel msgStrcmp3]
+	lea	rdi, [rel msgStrcmp4]
 	call	printf
 	; TEST: strcmp(str1, str4)
 	lea	rdi, [rel str1]
@@ -688,7 +701,15 @@ main:
 	call	strcmp
 	mov	rsi, rax
 	xor	rax, rax
-	lea	rdi, [rel msgStrcmp4]
+	lea	rdi, [rel msgStrcmp5]
+	call	printf
+	; TEST: strcmp(str1, str1)
+	lea	rdi, [rel str1]
+	mov	rsi, rdi
+	call	strcmp
+	mov	rsi, rax
+	xor	rax, rax
+	lea	rdi, [rel msgStrcmp6]
 	call	printf
 %ENDIF