From 181995b44fdce366645205c2d73312115f0961ee Mon Sep 17 00:00:00 2001
From: "Ryan C. Gordon" <[EMAIL REDACTED]>
Date: Sat, 4 Jan 2025 21:53:05 -0500
Subject: [PATCH] stdlib: Reworked SDL_vswprintf to be more efficient and
return correct values.
Fixes #11729.
---
src/stdlib/SDL_string.c | 62 +++++++++++++++++++++++++++--------------
1 file changed, 41 insertions(+), 21 deletions(-)
diff --git a/src/stdlib/SDL_string.c b/src/stdlib/SDL_string.c
index 50da685f7eb57..39c49e46173fd 100644
--- a/src/stdlib/SDL_string.c
+++ b/src/stdlib/SDL_string.c
@@ -2346,9 +2346,7 @@ int SDL_vsnprintf(SDL_OUT_Z_CAP(maxlen) char *text, size_t maxlen, SDL_PRINTF_FO
int SDL_vswprintf(SDL_OUT_Z_CAP(maxlen) wchar_t *text, size_t maxlen, const wchar_t *fmt, va_list ap)
{
- char *text_utf8 = NULL, *fmt_utf8 = NULL;
- int result;
-
+ char *fmt_utf8 = NULL;
if (fmt) {
fmt_utf8 = SDL_iconv_string("UTF-8", "WCHAR_T", (const char *)fmt, (SDL_wcslen(fmt) + 1) * sizeof(wchar_t));
if (!fmt_utf8) {
@@ -2356,34 +2354,56 @@ int SDL_vswprintf(SDL_OUT_Z_CAP(maxlen) wchar_t *text, size_t maxlen, const wcha
}
}
- if (!maxlen) {
- // We still need to generate the text to find the final text length
- maxlen = 1024;
- }
- text_utf8 = (char *)SDL_malloc(maxlen * 4);
- if (!text_utf8) {
+ char tinybuf[64]; // for really small strings, calculate it once.
+
+ // generate the text to find the final text length
+ va_list aq;
+ va_copy(aq, ap);
+ const int utf8len = SDL_vsnprintf(tinybuf, sizeof (tinybuf), fmt_utf8, aq);
+ va_end(aq);
+
+ if (utf8len < 0) {
SDL_free(fmt_utf8);
return -1;
}
- result = SDL_vsnprintf(text_utf8, maxlen * 4, fmt_utf8, ap);
+ bool isstack = false;
+ char *smallbuf = NULL;
+ char *utf8buf;
+ int result;
- if (result >= 0) {
- wchar_t *text_wchar = (wchar_t *)SDL_iconv_string("WCHAR_T", "UTF-8", text_utf8, SDL_strlen(text_utf8) + 1);
- if (text_wchar) {
- if (text) {
- SDL_wcslcpy(text, text_wchar, maxlen);
- }
- result = (int)SDL_wcslen(text_wchar);
- SDL_free(text_wchar);
- } else {
- result = -1;
+ if (utf8len < sizeof (tinybuf)) { // whole thing fit in the stack buffer, just use that copy.
+ utf8buf = tinybuf;
+ } else { // didn't fit in the stack buffer, allocate the needed space and run it again.
+ utf8buf = smallbuf = SDL_small_alloc(char, utf8len + 1, &isstack);
+ if (!smallbuf) {
+ SDL_free(fmt_utf8);
+ return -1; // oh well.
+ }
+ const int utf8len2 = SDL_vsnprintf(smallbuf, utf8len + 1, fmt_utf8, ap);
+ if (utf8len2 > utf8len) {
+ SDL_free(fmt_utf8);
+ return SDL_SetError("Formatted output changed between two runs"); // race condition on the parameters, and we no longer have room...yikes.
}
}
- SDL_free(text_utf8);
SDL_free(fmt_utf8);
+ wchar_t *wbuf = (wchar_t *)SDL_iconv_string("WCHAR_T", "UTF-8", utf8buf, utf8len + 1);
+ if (wbuf) {
+ if (text) {
+ SDL_wcslcpy(text, wbuf, maxlen);
+ }
+ result = (int)SDL_wcslen(wbuf);
+ SDL_free(wbuf);
+ } else {
+ result = -1;
+ }
+
+ if (smallbuf != NULL) {
+ SDL_small_free(smallbuf, isstack);
+ }
+
return result;
}