From cc7343daf561542ce3be1dcaecffce72ced5e5e5 Mon Sep 17 00:00:00 2001
From: MarcZX100 <marczxrr@gmail.com>
Date: Wed, 7 Oct 2026 23:12:33 +0000
Subject: [PATCH] fix(libc): clear fopen_s output on invalid arguments

(cherry picked from commit 387279ee941e5a203325852b24cdb87e2f835e43)
---
 core/libs/prx/libc/src/FileAndHeap.cpp |  4 +++-
 core/libs/tests/GuestFiopen.cpp        | 18 ++++++++++++++++++
 2 files changed, 21 insertions(+), 1 deletion(-)

diff --git a/core/libs/prx/libc/src/FileAndHeap.cpp b/core/libs/prx/libc/src/FileAndHeap.cpp
index 20527e876..4b23cd2f0 100644
--- a/core/libs/prx/libc/src/FileAndHeap.cpp
+++ b/core/libs/prx/libc/src/FileAndHeap.cpp
@@ -138,7 +138,9 @@ FileStream* APS5_VABI fopen_nid_postfix(const char* filename, const char* mode)
 int APS5_VABI fopen_s_nid_postfix(FileStream** result, const char* filename, const char* mode) {
     constexpr int GuestEinval = 22;
     constexpr int GuestEnoent = 2;
-    if (!result || !filename || !mode) return GuestEinval;
+    if (!result) return GuestEinval;
+    *result = nullptr;
+    if (!filename || !mode) return GuestEinval;
     *result = fopen_nid_postfix(filename, mode);
     return *result ? 0 : GuestEnoent;
 }
diff --git a/core/libs/tests/GuestFiopen.cpp b/core/libs/tests/GuestFiopen.cpp
index 6c2636ae3..86b28cb98 100644
--- a/core/libs/tests/GuestFiopen.cpp
+++ b/core/libs/tests/GuestFiopen.cpp
@@ -10,6 +10,7 @@
 extern "C" {
 FileStream* APS5_VABI _ZSt7_FiopenPKcNSt5_IosbIiE9_OpenmodeEi_nid_postfix(const char*, int, int);
 FileStream* APS5_VABI fopen_nid_postfix(const char*, const char*);
+int APS5_VABI fopen_s_nid_postfix(FileStream**, const char*, const char*);
 int APS5_VABI fclose_nid_postfix(FileStream*);
 std::int64_t APS5_VABI ftello_nid_postfix(FileStream*);
 }
@@ -24,6 +25,8 @@ static void Check(bool value, int line) {
 
 constexpr int In = 0x01, Out = 0x02, Ate = 0x04, App = 0x08, Trunc = 0x10, Nocreate = 0x20, Noreplace = 0x40,
     Binary = 0x80;
+constexpr int GuestEinval = 22;
+constexpr int GuestEnoent = 2;
 
 static FileStream* Open(const char* name, int mode) {
     return _ZSt7_FiopenPKcNSt5_IosbIiE9_OpenmodeEi_nid_postfix(name, mode, 0x1b6);
@@ -66,6 +69,21 @@ int main() {
     Write(Open(file, Out), "abc");
     Require(Contents(file) == "abc");
 
+    FileStream* checkedStream = &_Stdout_nid_postfix;
+    Require(fopen_s_nid_postfix(&checkedStream, nullptr, "rb") == GuestEinval);
+    Require(checkedStream == nullptr);
+    checkedStream = &_Stderr_nid_postfix;
+    Require(fopen_s_nid_postfix(&checkedStream, file, nullptr) == GuestEinval);
+    Require(checkedStream == nullptr);
+    Require(fopen_s_nid_postfix(nullptr, file, "rb") == GuestEinval);
+    checkedStream = &_Stdout_nid_postfix;
+    Require(fopen_s_nid_postfix(&checkedStream, file, "rb") == 0);
+    Require(checkedStream != nullptr);
+    Require(fclose_nid_postfix(checkedStream) == 0);
+    checkedStream = &_Stdout_nid_postfix;
+    Require(fopen_s_nid_postfix(&checkedStream, missing, "rb") == GuestEnoent);
+    Require(checkedStream == nullptr);
+
     auto* stream = Open(file, In);
     Require(stream != nullptr && std::fgetc(stream->GetHandle()) == 'a');
     fclose_nid_postfix(stream);