6 files changed, 14 insertions, 36 deletions
diff --git a/core/src/fxcrt/fx_basic_bstring.cpp b/core/src/fxcrt/fx_basic_bstring.cpp
index d5ffcddb6d..c706912d9d 100644
--- a/core/src/fxcrt/fx_basic_bstring.cpp
+++ b/core/src/fxcrt/fx_basic_bstring.cpp
@@ -493,7 +493,7 @@ void CFX_ByteString::FormatV(const FX_CHAR* lpszFormat, va_list argList) {
     }
     if (nWidth == 0) {
       nWidth = FXSYS_atoi(lpsz);
-      for (; std::isdigit(*lpsz); lpsz++)
+      for (; (*lpsz) >= '0' && (*lpsz) <= '9'; lpsz++)
         ;
     }
     if (nWidth < 0 || nWidth > 128 * 1024) {
@@ -509,7 +509,7 @@ void CFX_ByteString::FormatV(const FX_CHAR* lpszFormat, va_list argList) {
         lpsz++;
       } else {
         nPrecision = FXSYS_atoi(lpsz);
-        for (; std::isdigit(*lpsz); lpsz++)
+        for (; (*lpsz) >= '0' && (*lpsz) <= '9'; lpsz++)
           ;
       }
     }
diff --git a/core/src/fxcrt/fx_basic_gcc.cpp b/core/src/fxcrt/fx_basic_gcc.cpp
index 71f5fe322f..6f17482156 100644
--- a/core/src/fxcrt/fx_basic_gcc.cpp
+++ b/core/src/fxcrt/fx_basic_gcc.cpp
@@ -12,20 +12,21 @@
 template <class T, class STR_T>
 T FXSYS_StrToInt(STR_T str) {
   FX_BOOL neg = FALSE;
-  if (!str)
+  if (str == NULL) {
     return 0;
-
+  }
   if (*str == '-') {
     neg = TRUE;
     str++;
   }
   T num = 0;
   while (*str) {
-    if (!std::isdigit(*str))
+    if ((*str) < '0' || (*str) > '9') {
       break;
-    if (num > (std::numeric_limits<T>::max() - 9) / 10)
+    }
+    if (num > (std::numeric_limits<T>::max() - 9) / 10) {
       break;
-
+    }
     num = num * 10 + (*str) - '0';
     str++;
   }
diff --git a/core/src/fxcrt/fx_basic_util.cpp b/core/src/fxcrt/fx_basic_util.cpp
index 71119082a2..46a0dec1e5 100644
--- a/core/src/fxcrt/fx_basic_util.cpp
+++ b/core/src/fxcrt/fx_basic_util.cpp
@@ -101,13 +101,13 @@ void FX_atonum(const CFX_ByteStringC& strc, FX_BOOL& bInteger, void* pData) {
       cc++;
     }
     while (cc < len) {
-      if (!std::isdigit(str[cc]))
+      if (str[cc] < '0' || str[cc] > '9') {
         break;
-
+      }
       integer = integer * 10 + str[cc] - '0';
-      if (integer < 0)
+      if (integer < 0) {
         break;
-
+      }
       cc++;
     }
     if (bNegative) {
diff --git a/core/src/fxcrt/fx_basic_wstring.cpp b/core/src/fxcrt/fx_basic_wstring.cpp
index 3310df7062..c097e1fc09 100644
--- a/core/src/fxcrt/fx_basic_wstring.cpp
+++ b/core/src/fxcrt/fx_basic_wstring.cpp
@@ -765,7 +765,7 @@ void CFX_WideString::FormatV(const FX_WCHAR* lpszFormat, va_list argList) {
     }
     if (nWidth == 0) {
       nWidth = FXSYS_wtoi(lpsz);
-      for (; *lpsz != 0 && std::isdigit(*lpsz); lpsz++)
+      for (; *lpsz != 0 && (*lpsz) <= '9' && (*lpsz) >= '0'; lpsz++)
         ;
     }
     if (nWidth < 0 || nWidth > 128 * 1024) {
@@ -781,7 +781,7 @@ void CFX_WideString::FormatV(const FX_WCHAR* lpszFormat, va_list argList) {
         lpsz++;
       } else {
         nPrecision = FXSYS_wtoi(lpsz);
-        for (; *lpsz != 0 && std::isdigit(*lpsz); lpsz++)
+        for (; *lpsz != 0 && (*lpsz) >= '0' && (*lpsz) <= '9'; lpsz++)
           ;
       }
     }
diff --git a/core/src/fxcrt/fx_extension.cpp b/core/src/fxcrt/fx_extension.cpp
index a75cfb48df..d64a06d08b 100644
--- a/core/src/fxcrt/fx_extension.cpp
+++ b/core/src/fxcrt/fx_extension.cpp
@@ -13,15 +13,6 @@
 #include <ctime>
 #endif
 
-#include <cctype>
-
-int HexCharToDigit(char c) {
-  if (!std::isxdigit(c))
-    return 0;
-  char upchar = std::toupper(c);
-  return upchar > '9' ? upchar - 'A' + 10 : upchar - '0';
-}
-
 IFX_FileStream* FX_CreateFileStream(const FX_CHAR* filename, FX_DWORD dwModes) {
   IFXCRT_FileAccess* pFA = FXCRT_FileAccess_Create();
   if (!pFA) {
diff --git a/core/src/fxcrt/fx_extension_unittest.cpp b/core/src/fxcrt/fx_extension_unittest.cpp
deleted file mode 100644
index e2017fc3ed..0000000000
--- a/core/src/fxcrt/fx_extension_unittest.cpp
+++ /dev/null
@@ -1,14 +0,0 @@
-// Copyright 2015 PDFium Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style license that can be
-// found in the LICENSE file.
-
-#include "testing/gtest/include/gtest/gtest.h"
-
-#include "../../include/fxcrt/fx_ext.h"
-
-TEST(fxcrt, HexCharToDigit) {
-  EXPECT_EQ(10, HexCharToDigit('a'));
-  EXPECT_EQ(10, HexCharToDigit('A'));
-  EXPECT_EQ(7, HexCharToDigit('7'));
-  EXPECT_EQ(0, HexCharToDigit('i'));
-}