From baaf1f548edaec11e90dc2aa730b612ae3c9f373 Mon Sep 17 00:00:00 2001
From: Dirk Stolle <striezel-dev@web.de>
Date: Sun, 12 Jul 2026 03:23:24 +0200
Subject: [PATCH] guard WideCharToMultiByte() against empty strings

This should fix <https://github.com/boostorg/process/issues/554>.
---
 src/detail/utf8.cpp | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/src/detail/utf8.cpp b/src/detail/utf8.cpp
index f6274cfc8..a657b120c 100644
--- a/src/detail/utf8.cpp
+++ b/src/detail/utf8.cpp
@@ -37,6 +37,8 @@ inline void handle_error(error_code & ec)
 
 std::size_t size_as_utf8(const wchar_t * in, std::size_t size, error_code & ec)
 {
+    if (size == 0u)
+        return 0u;
     auto res = WideCharToMultiByte(
                           CP_UTF8,                // CodePage,
                           0,                      // dwFlags,
@@ -72,6 +74,8 @@ std::size_t size_as_wide(const char * in, std::size_t size, error_code & ec)
 std::size_t convert_to_utf8(const wchar_t *in, std::size_t size,  char * out, 
                             std::size_t max_size, error_code & ec)
 {
+    if (size == 0u)
+        return 0u;
     auto res = ::WideCharToMultiByte(
                     CP_UTF8,                    // CodePage
                     0,                          // dwFlags