From 5a5f6e50c725e80e433466bd9b516a34dc6ab491 Mon Sep 17 00:00:00 2001
From: sit-d <281093367+sit-d@users.noreply.github.com>
Date: Sun, 5 Jul 2026 03:59:51 -0600
Subject: [PATCH] fix: copy va_list before formatter retries

---
 errnfo.c  | 8 +++++---
 modsnap.c | 9 +++++++--
 wchain.c  | 9 +++++++--
 3 files changed, 19 insertions(+), 7 deletions(-)

diff --git a/errnfo.c b/errnfo.c
index 038364d..684636b 100644
--- a/errnfo.c
+++ b/errnfo.c
@@ -144,11 +144,14 @@ static void errw(const wchar_t* s) {
 
 static void vfmt_to(HANDLE h, bool is_console, const wchar_t* fmt, va_list ap) {
     wchar_t stackbuf[2048];
+    va_list ap2;
+    va_copy(ap2, ap);
 #if defined(_MSC_VER)
-    int n = _vsnwprintf_s(stackbuf, _countof(stackbuf), _TRUNCATE, fmt, ap);
+    int n = _vsnwprintf_s(stackbuf, _countof(stackbuf), _TRUNCATE, fmt, ap2);
 #else
-    int n = vswprintf(stackbuf, (int)(sizeof(stackbuf) / sizeof(stackbuf[0])), fmt, ap);
+    int n = vswprintf(stackbuf, (int)(sizeof(stackbuf) / sizeof(stackbuf[0])), fmt, ap2);
 #endif
+    va_end(ap2);
     if (n >= 0) {
         write_w(h, is_console, stackbuf);
         return;
@@ -158,7 +161,6 @@ static void vfmt_to(HANDLE h, bool is_console, const wchar_t* fmt, va_list ap) {
     wchar_t* dyn = (wchar_t*)malloc(cap * sizeof(wchar_t));
     if (!dyn) return;
 
-    va_list ap2;
     va_copy(ap2, ap);
 #if defined(_MSC_VER)
     _vsnwprintf_s(dyn, cap, _TRUNCATE, fmt, ap2);
diff --git a/modsnap.c b/modsnap.c
index 2021466..f45f322 100644
--- a/modsnap.c
+++ b/modsnap.c
@@ -92,7 +92,10 @@ static void errw(const wchar_t* s) {
 
 static void vfmt_to(HANDLE h, bool is_console, const wchar_t* fmt, va_list ap) {
     wchar_t stackbuf[2048];
-    int n = _vsnwprintf_s(stackbuf, _countof(stackbuf), _TRUNCATE, fmt, ap);
+    va_list copy;
+    va_copy(copy, ap);
+    int n = _vsnwprintf_s(stackbuf, _countof(stackbuf), _TRUNCATE, fmt, copy);
+    va_end(copy);
     if (n >= 0) {
         write_w(h, is_console, stackbuf);
         return;
@@ -103,7 +106,9 @@ static void vfmt_to(HANDLE h, bool is_console, const wchar_t* fmt, va_list ap) {
         wchar_t* dyn = (wchar_t*)malloc(cap * sizeof(wchar_t));
         if (!dyn) return;
 
-        _vsnwprintf_s(dyn, cap, _TRUNCATE, fmt, ap);
+        va_copy(copy, ap);
+        _vsnwprintf_s(dyn, cap, _TRUNCATE, fmt, copy);
+        va_end(copy);
         write_w(h, is_console, dyn);
         free(dyn);
     }
diff --git a/wchain.c b/wchain.c
index 4383946..7e4add5 100644
--- a/wchain.c
+++ b/wchain.c
@@ -143,7 +143,10 @@ static void errw(const wchar_t* s) {
 
 static void vfmt_to(HANDLE h, bool is_console, const wchar_t* fmt, va_list ap) {
     wchar_t stackbuf[2048];
-    int n = _vsnwprintf_s(stackbuf, _countof(stackbuf), _TRUNCATE, fmt, ap);
+    va_list copy;
+    va_copy(copy, ap);
+    int n = _vsnwprintf_s(stackbuf, _countof(stackbuf), _TRUNCATE, fmt, copy);
+    va_end(copy);
     if (n >= 0) {
         write_w(h, is_console, stackbuf);
         return;
@@ -154,7 +157,9 @@ static void vfmt_to(HANDLE h, bool is_console, const wchar_t* fmt, va_list ap) {
         wchar_t* dyn = (wchar_t*)HeapAlloc(GetProcessHeap(), 0, cap * sizeof(wchar_t));
         if (!dyn) return;
 
-        _vsnwprintf_s(dyn, cap, _TRUNCATE, fmt, ap);
+        va_copy(copy, ap);
+        _vsnwprintf_s(dyn, cap, _TRUNCATE, fmt, copy);
+        va_end(copy);
         write_w(h, is_console, dyn);
         HeapFree(GetProcessHeap(), 0, dyn);
     }