From 6bc60004540c0e3ce3d24836661856720ce702c4 Mon Sep 17 00:00:00 2001
From: Kwarde <kevin@kwarde.com>
Date: Sun, 20 Jul 2025 12:35:13 +0200
Subject: [PATCH] printf: Prevent special characters not being processed if it
 was proceeded by a percentage sign (ie '%\n')

---
 src/console.asm | 10 ++++++++++
 src/tests.asm   | 31 +++++++++++++++++++------------
 2 files changed, 29 insertions(+), 12 deletions(-)

diff --git a/src/console.asm b/src/console.asm
index 8b08758..18a7533 100644
--- a/src/console.asm
+++ b/src/console.asm
@@ -295,6 +295,8 @@ printf:
 
 		;--- Invalid ---;
 		.invalidReplacement:
+		cmp	byte [rdi + 1], '\'
+		je	.invalidReplacement_specialChar; '%\n' would become "'%','\','n'" instead of "'%',EOS" when inserting full invalid specifier.
 		mov	r9w, word [rdi]
 		mov	[printfBuff+r10], r9w
 		add	rdi, 2
@@ -302,6 +304,14 @@ printf:
 		add	r11, 2
 		inc	r14
 		jmp	.process
+		.invalidReplacement_specialChar:
+		mov	r9b, byte [rdi]
+		mov	[printfBuff+r10], r9b
+		inc	rdi
+		inc	r10
+		inc	r11
+		inc	r14
+		jmp	.process
 
 		;--- '%%' ---;
 		.rep_pct:
diff --git a/src/tests.asm b/src/tests.asm
index 35f508d..6911f93 100644
--- a/src/tests.asm
+++ b/src/tests.asm
@@ -64,14 +64,14 @@ section .rodata
 
 	; printf()
 	msgPrintf		db	NL,"TEST printf()",NL,EOS
-	printf1			db	TAB,"printf(",DQUO,"He%ll%o there%%%%%!%!%\n",DQUO,"): ",NL,TAB,TAB,EOS
-	printf1Str		db	"He%ll%o there%%%%%!%!%",NL,EOS
+	printf1			db	TAB,"printf(",DQUO,"He%ll%0 there%%%%%!%!%\n",DQUO,"): ",NL,TAB,TAB,EOS
+	printf1Str		db	"He%ll%0 there%%%%%!%!%\n",EOS
 	printf2			db	TAB,"printf(",DQUO,"Are %s doing %s?\n",DQUO,", printf2Str1, printf2Str2): ",NL,TAB,TAB,EOS
-	printf2Str		db	"Are %s doing %s?",NL,EOS
+	printf2Str		db	"Are %s doing %s?\n",EOS
 	printf2Str1		db	"you",EOS
 	printf2Str2		db	"okay",EOS
 	printf3			db	TAB,"printf(",DQUO,"%c%c%c%c%c there %c%c %s%c\n",DQUO,", 'H', 'e', 'l', 'l', 'o', 'm', 'y', ",DQUO,"friend",DQUO,", '!'): ",NL,TAB,TAB,EOS
-	printf3Str		db	"%c%c%c%c%c there %c%c %s%c",NL,EOS
+	printf3Str		db	"%c%c%c%c%c there %c%c %s%c\n",EOS
 	printf3C1		equ	'H'
 	printf3C2		equ	'e'
 	printf3C3		equ	'l'
@@ -82,21 +82,21 @@ section .rodata
 	printf3Str1		db	"friend",EOS
 	printf3C8		equ	'!'
 	printf4			db	TAB,"printf(",DQUO,"%i|%d|%u , %i|%d|%u\n",DQUO,", -50, -50, -50, 0xFFFFFFFFFFFFFFFF, 0xFFFFFFFFFFFFFFFF, 0xFFFFFFFFFFFFFFFF): ",NL,TAB,TAB,EOS
-	printf4Str		db	"%i|%d|%u , %i|%d|%u",NL,EOS
+	printf4Str		db	"%i|%d|%u , %i|%d|%u\n",EOS
 	printf5			db	TAB,"printf(",DQUO,"%x|%X , %x|%X\n",DQUO,", 0xabcdeffedcba, 0x069bc0e, 666, -1): ",NL,TAB,TAB,EOS
-	printf5Str		db	"%x|%X , %x|%X",NL,EOS
+	printf5Str		db	"%x|%X , %x|%X\n",EOS
 	printf6			db	TAB,"printf(",DQUO,"%b | %8b | %08b\n",DQUO,", 5, 7, 9): ",NL,TAB,TAB,EOS
-	printf6Str		db	"%b | %8b | %08b",NL,EOS
+	printf6Str		db	"%b | %8b | %08b\n",EOS
 	printf7			db	TAB,"printf(",DQUO,"%d | %8d | %08d\n",DQUO,", -234, -666, 234): ",NL,TAB,TAB,EOS
-	printf7Str		db	"%d | %8d | %08d",NL,EOS
+	printf7Str		db	"%d | %8d | %08d\n",EOS
 	printf8			db	TAB,"printf(",DQUO,"%i | %8i | %08i\n",DQUO,", -234, -666, 234): ",NL,TAB,TAB,EOS
-	printf8Str		db	"%i | %8i | %08i",NL,EOS
+	printf8Str		db	"%i | %8i | %08i\n",EOS
 	printf9			db	TAB,"printf(",DQUO,"%u | %8u | %08u\n",DQUO,", -234, -666, 234): ",NL,TAB,TAB,EOS
-	printf9Str		db	"%u | %8u | %08u",NL,EOS
+	printf9Str		db	"%u | %8u | %08u\n",EOS
 	printf10		db	TAB,"printf(",DQUO,"%x | %8x | %08x\n",DQUO,", 0xAB0F, 0xBA0F, 0xAB0F): ",NL,TAB,TAB,EOS
-	printf10Str		db	"%x | %8x | %08x",NL,EOS
+	printf10Str		db	"%x | %8x | %08x\n",EOS
 	printf11		db	TAB,"printf(",DQUO,"%X | %8X | %08X\n",DQUO,", 0xAB0F, 0xBA0F, 0xAB0F): ",NL,TAB,TAB,EOS
-	printf11Str		db	"%X | %8X | %08X",NL,EOS
+	printf11Str		db	"%X | %8X | %08X\n",EOS
 	printf12		db	TAB,"rax=0x1234567890ABCDEF",NL,TAB,"printf(",DQUO,"\nRAX\t%064b\nEAX\t\t\t\t\t%032b\n AX\t\t\t\t\t\t\t%016b\n AH\t\t\t\t\t\t\t%08b\t\n AL\t\t\t\t\t\t\t\t%08b\n",DQUO,", rax, eax, ax, ah, al): ",NL,TAB,TAB,EOS
 	printf12Str		db	"\nRAX\t%064b\nEAX\t\t\t\t\t%032b\n AX\t\t\t\t\t\t\t%016b\n AH\t\t\t\t\t\t\t%08b\t\n AL\t\t\t\t\t\t\t\t%08b\n",EOS
 	printf13		db	TAB,"printf(",DQUO,"%o | %8o | %08o\n",DQUO,", 1500, 1500, 1500): ",NL,TAB,TAB,EOS
@@ -107,6 +107,8 @@ section .rodata
 	printf15Str		db	"%p | %#p | %8p | %#8p | %08p | %#08p\n",EOS
 	printf16		db	TAB,"printf(",DQUO,"%x | %#10x | %10x | %#10x | %010x | %#010x\n",DQUO,", str5, str5, str5, str5, strBuff1, strBuff1): ",NL,TAB,TAB,EOS
 	printf16Str		db	"%x | %#10x | %10x | %#10x | %010x | %#010x\n",EOS
+	printf17		db	TAB,"printf(",DQUO,"Ran\dom in\v\a\li%\d test%\n",DQUO,"): ",NL,TAB,TAB,EOS
+	printf17Str		db	"Ran\dom in\v\a\li%\d test%\n",EOS
 	; strlen()
 	msgStrlen		db	NL,"TEST strlen()",NL,EOS
 	strlen1			db	TAB,"strlen(str1): %d",NL,EOS
@@ -444,6 +446,11 @@ _start:
 	push	strBuff1
 	call	printf
 	add	rsp, SIZE_QWORD * 2
+
+	lea	rdi, [rel printf17]
+	call	print
+	lea	rdi, [rel printf17Str]
+	call	printf
 %endif
 
 ;---