diff --git a/core/fpdfapi/parser/fpdf_parser_utility.cpp b/core/fpdfapi/parser/fpdf_parser_utility.cpp
index 7025b3e..8323426 100644
--- a/core/fpdfapi/parser/fpdf_parser_utility.cpp
+++ b/core/fpdfapi/parser/fpdf_parser_utility.cpp
@@ -147,7 +147,7 @@
     }
   }
   dest_buf[dest_len] = 0;
-  res.ReleaseBuffer();
+  res.ReleaseBuffer(res.GetStringLength());
   return res;
 }
 
diff --git a/core/fpdftext/cpdf_textpagefind.cpp b/core/fpdftext/cpdf_textpagefind.cpp
index adef9f6..3c8e532 100644
--- a/core/fpdftext/cpdf_textpagefind.cpp
+++ b/core/fpdftext/cpdf_textpagefind.cpp
@@ -377,7 +377,7 @@
                      : (int)FXSYS_wcslen(lpszFullString);
   ASSERT(nLen >= 0);
   memcpy(rString.GetBuffer(nLen), lpszFullString, nLen * sizeof(wchar_t));
-  rString.ReleaseBuffer();
+  rString.ReleaseBuffer(rString.GetStringLength());
   return true;
 }
 
diff --git a/core/fxcrt/cfx_bytestring.cpp b/core/fxcrt/cfx_bytestring.cpp
index 6e01933..5dcaf61 100644
--- a/core/fxcrt/cfx_bytestring.cpp
+++ b/core/fxcrt/cfx_bytestring.cpp
@@ -361,12 +361,10 @@
 }
 
 void CFX_ByteString::ReleaseBuffer(FX_STRSIZE nNewLength) {
+  ASSERT(nNewLength >= 0);
   if (!m_pData)
     return;
 
-  if (nNewLength == -1)
-    nNewLength = FXSYS_strlen(m_pData->m_String);
-
   nNewLength = std::min(nNewLength, m_pData->m_nAllocLength);
   if (nNewLength == 0) {
     clear();
@@ -507,7 +505,7 @@
       // 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);
-      ReleaseBuffer();
+      ReleaseBuffer(GetStringLength());
     }
   }
   va_end(argListSave);
diff --git a/core/fxcrt/cfx_bytestring.h b/core/fxcrt/cfx_bytestring.h
index 519cee3..8bd9f39 100644
--- a/core/fxcrt/cfx_bytestring.h
+++ b/core/fxcrt/cfx_bytestring.h
@@ -79,6 +79,9 @@
   }
 
   FX_STRSIZE GetLength() const { return m_pData ? m_pData->m_nDataLength : 0; }
+  FX_STRSIZE GetStringLength() const {
+    return m_pData ? FXSYS_strlen(m_pData->m_String) : 0;
+  }
   bool IsEmpty() const { return !GetLength(); }
 
   int Compare(const CFX_ByteStringC& str) const;
@@ -122,7 +125,7 @@
 
   void Reserve(FX_STRSIZE len);
   char* GetBuffer(FX_STRSIZE len);
-  void ReleaseBuffer(FX_STRSIZE len = -1);
+  void ReleaseBuffer(FX_STRSIZE len);
 
   CFX_ByteString Mid(FX_STRSIZE first, FX_STRSIZE count) const;
   CFX_ByteString Left(FX_STRSIZE count) const;
diff --git a/core/fxcrt/cfx_bytestring_unittest.cpp b/core/fxcrt/cfx_bytestring_unittest.cpp
index d7f265e..4379519 100644
--- a/core/fxcrt/cfx_bytestring_unittest.cpp
+++ b/core/fxcrt/cfx_bytestring_unittest.cpp
@@ -653,7 +653,7 @@
     char* buffer = str.GetBuffer(12);
     // NOLINTNEXTLINE(runtime/printf)
     strcpy(buffer, "clams");
-    str.ReleaseBuffer();
+    str.ReleaseBuffer(str.GetStringLength());
     EXPECT_EQ("clams", str);
   }
   {
@@ -661,7 +661,7 @@
     char* buffer = str.GetBuffer(12);
     // NOLINTNEXTLINE(runtime/printf)
     strcpy(buffer + 2, "ams");
-    str.ReleaseBuffer();
+    str.ReleaseBuffer(str.GetStringLength());
     EXPECT_EQ("clams", str);
   }
 }
diff --git a/core/fxcrt/cfx_widestring.cpp b/core/fxcrt/cfx_widestring.cpp
index 8937783..b837523 100644
--- a/core/fxcrt/cfx_widestring.cpp
+++ b/core/fxcrt/cfx_widestring.cpp
@@ -488,12 +488,10 @@
 }
 
 void CFX_WideString::ReleaseBuffer(FX_STRSIZE nNewLength) {
+  ASSERT(nNewLength >= 0);
   if (!m_pData)
     return;
 
-  if (nNewLength == -1)
-    nNewLength = FXSYS_wcslen(m_pData->m_String);
-
   nNewLength = std::min(nNewLength, m_pData->m_nAllocLength);
   if (nNewLength == 0) {
     clear();
@@ -651,7 +649,7 @@
   memset(m_pData->m_String, 0, (size + 1) * sizeof(wchar_t));
   int ret = vswprintf(m_pData->m_String, size + 1, pFormat, argList);
   bool bSufficientBuffer = ret >= 0 || m_pData->m_String[size - 1] == 0;
-  ReleaseBuffer();
+  ReleaseBuffer(GetStringLength());
   return bSufficientBuffer;
 }
 
diff --git a/core/fxcrt/cfx_widestring.h b/core/fxcrt/cfx_widestring.h
index 938b1e7..02045c5 100644
--- a/core/fxcrt/cfx_widestring.h
+++ b/core/fxcrt/cfx_widestring.h
@@ -75,6 +75,9 @@
   void clear() { m_pData.Reset(); }
 
   FX_STRSIZE GetLength() const { return m_pData ? m_pData->m_nDataLength : 0; }
+  FX_STRSIZE GetStringLength() const {
+    return m_pData ? FXSYS_wcslen(m_pData->m_String) : 0;
+  }
   bool IsEmpty() const { return !GetLength(); }
 
   const CFX_WideString& operator=(const wchar_t* str);
@@ -135,7 +138,7 @@
 
   void Reserve(FX_STRSIZE len);
   wchar_t* GetBuffer(FX_STRSIZE len);
-  void ReleaseBuffer(FX_STRSIZE len = -1);
+  void ReleaseBuffer(FX_STRSIZE len);
 
   int GetInteger() const;
   float GetFloat() const;
diff --git a/core/fxcrt/cfx_widestring_unittest.cpp b/core/fxcrt/cfx_widestring_unittest.cpp
index a53e9a3..b743a17 100644
--- a/core/fxcrt/cfx_widestring_unittest.cpp
+++ b/core/fxcrt/cfx_widestring_unittest.cpp
@@ -618,14 +618,14 @@
     CFX_WideString str;
     wchar_t* buffer = str.GetBuffer(12);
     wcscpy(buffer, L"clams");
-    str.ReleaseBuffer();
+    str.ReleaseBuffer(str.GetStringLength());
     EXPECT_EQ(L"clams", str);
   }
   {
     CFX_WideString str(L"cl");
     wchar_t* buffer = str.GetBuffer(12);
     wcscpy(buffer + 2, L"ams");
-    str.ReleaseBuffer();
+    str.ReleaseBuffer(str.GetStringLength());
     EXPECT_EQ(L"clams", str);
   }
 }
diff --git a/fpdfsdk/cpdfsdk_formfillenvironment.cpp b/fpdfsdk/cpdfsdk_formfillenvironment.cpp
index 5c847fc..0a8a59c 100644
--- a/fpdfsdk/cpdfsdk_formfillenvironment.cpp
+++ b/fpdfsdk/cpdfsdk_formfillenvironment.cpp
@@ -376,7 +376,7 @@
   CFX_ByteString bsTo = CFX_WideString(wsURL).UTF16LE_Encode();
   FPDF_WIDESTRING pTo = (FPDF_WIDESTRING)bsTo.GetBuffer(wsURL.GetLength());
   m_pInfo->FFI_GotoURL(m_pInfo, document, pTo);
-  bsTo.ReleaseBuffer();
+  bsTo.ReleaseBuffer(bsTo.GetStringLength());
 }
 
 void CPDFSDK_FormFillEnvironment::GetPageViewRect(CPDFXFA_Page* page,
diff --git a/fpdfsdk/cpdfsdk_interform.cpp b/fpdfsdk/cpdfsdk_interform.cpp
index c973612..552bb31 100644
--- a/fpdfsdk/cpdfsdk_interform.cpp
+++ b/fpdfsdk/cpdfsdk_interform.cpp
@@ -482,10 +482,10 @@
     CFX_ByteString csValue_b = CFX_ByteString::FromUnicode(csWValue);
 
     fdfEncodedData << name_b.GetBuffer(name_b.GetLength());
-    name_b.ReleaseBuffer();
+    name_b.ReleaseBuffer(name_b.GetStringLength());
     fdfEncodedData << "=";
     fdfEncodedData << csValue_b.GetBuffer(csValue_b.GetLength());
-    csValue_b.ReleaseBuffer();
+    csValue_b.ReleaseBuffer(csValue_b.GetStringLength());
     if (i != pFields->GetCount() - 1)
       fdfEncodedData << "&";
   }
diff --git a/fpdfsdk/fpdfxfa/cpdfxfa_docenvironment.cpp b/fpdfsdk/fpdfxfa/cpdfxfa_docenvironment.cpp
index 7cccd2f..c12314f 100644
--- a/fpdfsdk/fpdfxfa/cpdfxfa_docenvironment.cpp
+++ b/fpdfsdk/fpdfxfa/cpdfxfa_docenvironment.cpp
@@ -976,11 +976,11 @@
         (FPDF_WIDESTRING)bsSubject.GetBuffer(bsSubject.GetLength());
     FPDF_WIDESTRING pMsg = (FPDF_WIDESTRING)bsMsg.GetBuffer(bsMsg.GetLength());
     pFormFillEnv->EmailTo(pFileHandler, pTo, pSubject, pCC, pBcc, pMsg);
-    bsTo.ReleaseBuffer();
-    bsCC.ReleaseBuffer();
-    bsBcc.ReleaseBuffer();
-    bsSubject.ReleaseBuffer();
-    bsMsg.ReleaseBuffer();
+    bsTo.ReleaseBuffer(bsTo.GetStringLength());
+    bsCC.ReleaseBuffer(bsCC.GetStringLength());
+    bsBcc.ReleaseBuffer(bsBcc.GetStringLength());
+    bsSubject.ReleaseBuffer(bsSubject.GetStringLength());
+    bsMsg.ReleaseBuffer(bsMsg.GetStringLength());
   } else {
     // HTTP or FTP
     CFX_WideString ws;
diff --git a/xfa/fde/cfde_txtedtbuf.cpp b/xfa/fde/cfde_txtedtbuf.cpp
index 1ec3c97..f1c73a9 100644
--- a/xfa/fde/cfde_txtedtbuf.cpp
+++ b/xfa/fde/cfde_txtedtbuf.cpp
@@ -118,7 +118,7 @@
     lpDstBuf += nCopyLength;
     nCopyLength = chunkHeader->nUsed;
   }
-  wsText.ReleaseBuffer();
+  wsText.ReleaseBuffer(wsText.GetStringLength());
 
   return wsText;
 }
diff --git a/xfa/fde/cfde_txtedtdorecord_insert.cpp b/xfa/fde/cfde_txtedtdorecord_insert.cpp
index fe79960..f752d91 100644
--- a/xfa/fde/cfde_txtedtdorecord_insert.cpp
+++ b/xfa/fde/cfde_txtedtdorecord_insert.cpp
@@ -18,7 +18,7 @@
   ASSERT(pEngine);
   wchar_t* lpBuffer = m_wsInsert.GetBuffer(nLength);
   memcpy(lpBuffer, lpText, nLength * sizeof(wchar_t));
-  m_wsInsert.ReleaseBuffer();
+  m_wsInsert.ReleaseBuffer(m_wsInsert.GetStringLength());
 }
 
 CFDE_TxtEdtDoRecord_Insert::~CFDE_TxtEdtDoRecord_Insert() {}