From 0aef3506b68991be0b7d956c6113edb823465b7a Mon Sep 17 00:00:00 2001
From: Hojun-Cho <ghwns6743@gmail.com>
Date: Sun, 16 Aug 2026 18:36:40 +0900
Subject: [PATCH] str: drop argument checks no caller can trip

sinit's nil and negative-length tests and stoutf's zero-size test only
had test callers; every real caller passes a buffer and its size. The
len > n check after fullrune succeeded could never fire.
---
 str.c            | 15 ++++-----------
 tests/str_test.c |  9 ---------
 2 files changed, 4 insertions(+), 20 deletions(-)

diff --git a/str.c b/str.c
index 173bd4d..72fa02f 100644
--- a/str.c
+++ b/str.c
@@ -1,6 +1,7 @@
 #include "dat.h"
 #include "fn.h"
 
+/* Fills s from n bytes of UTF-8; whole, valid, and at most Maxrunes. */
 int
 sinit(Str *s, char *src, int n)
 {
@@ -8,19 +9,12 @@ sinit(Str *s, char *src, int n)
 	Rune r;
 	int len;
 
-	if(s == nil)
-		return 0;
 	s->n = 0;
-	if(n < 0 || (n > 0 && src == nil))
-		return 0;
 	while(n > 0){
-		if(tmp.n >= Maxrunes)
-			return 0;
-		if(!fullrune(src, n))
+		if(tmp.n >= Maxrunes || !fullrune(src, n))
 			return 0;
 		len = chartorune(&r, src);
-		if(len > n || (r == Runeerror && len == 1) ||
-		   (r >= 0xd800 && r <= 0xdfff))
+		if((r == Runeerror && len == 1) || (r >= 0xd800 && r <= 0xdfff))
 			return 0;
 		tmp.r[tmp.n++] = r;
 		src += len;
@@ -75,14 +69,13 @@ scmp(Str *a, Str *b)
 	return 0;
 }
 
+/* UTF-8 of s into buf[sz], NUL-terminated, whole runes only. */
 int
 stoutf(Str *s, char *buf, int sz)
 {
 	char tmp[UTFmax];
 	int i, n, len;
 
-	if(sz <= 0)
-		return 0;
 	n = 0;
 	for(i = 0; i < s->n; i++){
 		len = runetochar(tmp, &s->r[i]);
diff --git a/tests/str_test.c b/tests/str_test.c
index cadf94b..d729340 100644
--- a/tests/str_test.c
+++ b/tests/str_test.c
@@ -76,7 +76,6 @@ str_utf8_capacity(struct ct *t)
 		int n;
 		char *want;
 	} cases[] = {
-		{ 0, 0, nil },
 		{ 1, 0, "" },
 		{ 2, 1, "a" },
 		{ 3, 1, "a" },
@@ -95,10 +94,6 @@ str_utf8_capacity(struct ct *t)
 		if(n != cases[i].n)
 			CT_ERRORF(t, "size %d: want length %d, got %d",
 				cases[i].size, cases[i].n, n);
-		if(cases[i].size == 0){
-			CT_EQ_INT(t, 'Z', buf[0]);
-			continue;
-		}
 		if(strcmp(cases[i].want, buf) != 0)
 			CT_ERRORF(t, "size %d: want \"%s\", got \"%s\"",
 				cases[i].size, cases[i].want, buf);
@@ -120,10 +115,6 @@ str_invalid_and_full_appends(struct ct *t)
 	Str s;
 	int i;
 
-	CT_CHECK(t, !sinit(&s, nil, 1));
-	CT_EQ_INT(t, 0, s.n);
-	CT_CHECK(t, !sinit(&s, "x", -1));
-	CT_EQ_INT(t, 0, s.n);
 	for(i = 0; i < Maxrunes; i++)
 		s.r[i] = 'a';
 	s.n = Maxrunes;