diff --git a/core/fxcrt/cfx_bytestring.cpp b/core/fxcrt/cfx_bytestring.cpp
index 20497ec..073591a 100644
--- a/core/fxcrt/cfx_bytestring.cpp
+++ b/core/fxcrt/cfx_bytestring.cpp
@@ -473,20 +473,22 @@
 }
 
 void CFX_ByteString::FormatV(const char* pFormat, va_list argList) {
-  va_list argListSave;
-  FX_VA_COPY(argListSave, argList);
-  FX_STRSIZE nMaxLen = vsnprintf(nullptr, 0, pFormat, argList);
+  va_list argListCopy;
+  va_copy(argListCopy, argList);
+  FX_STRSIZE nMaxLen = vsnprintf(nullptr, 0, pFormat, argListCopy);
+  va_end(argListCopy);
   if (nMaxLen > 0) {
     GetBuffer(nMaxLen);
     if (m_pData) {
       // In the following two calls, there's always space in the buffer for
       // a terminating NUL that's not included in nMaxLen.
       memset(m_pData->m_String, 0, nMaxLen + 1);
-      vsnprintf(m_pData->m_String, nMaxLen + 1, pFormat, argListSave);
+      va_copy(argListCopy, argList);
+      vsnprintf(m_pData->m_String, nMaxLen + 1, pFormat, argListCopy);
+      va_end(argListCopy);
       ReleaseBuffer(GetStringLength());
     }
   }
-  va_end(argListSave);
 }
 
 void CFX_ByteString::Format(const char* pFormat, ...) {
diff --git a/core/fxcrt/cfx_widestring.cpp b/core/fxcrt/cfx_widestring.cpp
index 24b7fb5..aadd1a2 100644
--- a/core/fxcrt/cfx_widestring.cpp
+++ b/core/fxcrt/cfx_widestring.cpp
@@ -665,17 +665,19 @@
 
 void CFX_WideString::FormatV(const wchar_t* format, va_list argList) {
   va_list argListCopy;
-  FX_VA_COPY(argListCopy, argList);
+  va_copy(argListCopy, argList);
   int maxLen = vswprintf(nullptr, 0, format, argListCopy);
   va_end(argListCopy);
   if (maxLen <= 0) {
+    va_copy(argListCopy, argList);
     auto guess = GuessSizeForVSWPrintf(format, argListCopy);
+    va_end(argListCopy);
     if (!guess.has_value())
       return;
     maxLen = pdfium::base::checked_cast<int>(guess.value());
   }
   while (maxLen < 32 * 1024) {
-    FX_VA_COPY(argListCopy, argList);
+    va_copy(argListCopy, argList);
     bool bSufficientBuffer =
         TryVSWPrintf(static_cast<FX_STRSIZE>(maxLen), format, argListCopy);
     va_end(argListCopy);
diff --git a/core/fxcrt/fx_system.h b/core/fxcrt/fx_system.h
index 600d71c..7a95bf4 100644
--- a/core/fxcrt/fx_system.h
+++ b/core/fxcrt/fx_system.h
@@ -263,13 +263,4 @@
 #define NEVER_INLINE __attribute__((__noinline__))
 #endif  // _FXM_PLATFORM_ == _FXM_PLATFORM_WINDOWS_
 
-// Handle differnces between platform's variadic function implementations.
-#if defined(__ARMCC_VERSION) ||                                              \
-    (!defined(_MSC_VER) && (_FX_CPU_ == _FX_X64_ || _FX_CPU_ == _FX_IA64_ || \
-                            _FX_CPU_ == _FX_ARM64_))
-#define FX_VA_COPY(dst, src) va_copy((dst), (src))
-#else
-#define FX_VA_COPY(dst, src) ((dst) = (src))
-#endif
-
 #endif  // CORE_FXCRT_FX_SYSTEM_H_