From f5e114313822914642a436ff22a7e2135ea06b1f Mon Sep 17 00:00:00 2001
From: Kwarde <kevin@kwarde.com>
Date: Wed, 25 Jun 2025 13:29:26 +0200
Subject: [PATCH] Fix issue in printf() with %d --needed to push+pop several
 registers before/after itoa() call

---
 console.asm | 14 ++++++++++----
 core.asm    |  5 +++++
 tests.asm   |  1 +
 3 files changed, 16 insertions(+), 4 deletions(-)

diff --git a/console.asm b/console.asm
index 9794263..f45605b 100644
--- a/console.asm
+++ b/console.asm
@@ -86,8 +86,7 @@ printf:
 			je	.rep_d_r9
 
 			;get from stack
-			; rsp + 5*8 : RIP to printf call (+1), PUSH rbp,r12,r13,rdi (+4)
-			mov	rsi, qword [rsp + 5*8 + (r10-5)*8]
+			mov	rsi, qword [rbp + 16 + (r10-5)*8]
 			jmp	.convertInt
 
 			.rep_d_rsi:
@@ -107,7 +106,15 @@ printf:
 
 			.convertInt:
 				lea	rsi, [rel printfNBuff]
+				push	rcx
+				push	rdx
+				push	r8
+				push	r10
 				call	itoa
+				pop	r10
+				pop	r8
+				pop	rdx
+				pop	rcx
 				mov	rsi, rax
 				jmp	.sinsertLoop
 
@@ -125,8 +132,7 @@ printf:
 			je	.rep_s_r9
 
 			;get from stack
-			; rsp + 5*8 : RIP to printf call (+1), PUSH rbp,r12,r13,rdi (+4)
-			mov	rsi, qword [rsp + 5*8 + (r10-5)*8]
+			mov	rsi, qword [rbp + 16 + (r10-5)*8]
 			jmp	.sinsertLoop
 
 			.rep_s_rdx:
diff --git a/core.asm b/core.asm
index 13a2a66..b3eb267 100644
--- a/core.asm
+++ b/core.asm
@@ -160,12 +160,17 @@ itoa:
 	inc	rcx
 	test	rax, rax
 	jnz	.convert
+	test	rbx, rbx
+	jz	.toString
+	push	byte '-'
+	inc	rcx
 
 	.toString:
 	pop	rdx
 	mov	byte [rsi], dl
 	inc	rsi
 	loop	.toString
+	mov	byte [rsi], 0
 
 	.quit:
 	pop	rsi
diff --git a/tests.asm b/tests.asm
index 51898f7..28b4edc 100644
--- a/tests.asm
+++ b/tests.asm
@@ -49,6 +49,7 @@ section	.rodata
 	TEST_toupper	equ	1
 	TEST_strcmp	equ	1
 	TEST_file1	equ	1
+	;TEST_itoa	equ	0 ; not included in these tests; printf() calls itoa for %d specifiers
 
 	num1		dq	69
 	num2		dq	0xFFFFFF