Re-enable several MSVC warnings

Re-enable the following warnings:
 4245: signed/unsigned conversion mismatch;
 4310: cast may truncate data;
 4389: operator on signed/unsigned mismatch;
 4701: use potentially uninitialized local variable;
 4706: assignment within conditional expression

Clean up the code to avoid those warnings.

BUG=pdfium:29
R=tsepez@chromium.org

Review URL: https://codereview.chromium.org/1801383002 .

4 files changed, 16 insertions, 13 deletions

diff --git a/core/fxcodec/codec/codec_int.h b/core/fxcodec/codec/codec_int.h
index d2f44dd674..d19a694222 100644
--- a/core/fxcodec/codec/codec_int.h
+++ b/core/fxcodec/codec/codec_int.h
@@ -47,7 +47,6 @@ class CCodec_ScanlineDecoder : public ICodec_ScanlineDecoder {
   ~CCodec_ScanlineDecoder() override;
 
   // ICodec_ScanlineDecoder
-  FX_DWORD GetSrcOffset() override { return -1; }
   void DownScale(int dest_width, int dest_height) override;
   const uint8_t* GetScanline(int line) override;
   FX_BOOL SkipToScanline(int line, IFX_Pause* pPause) override;
diff --git a/core/fxcodec/codec/fx_codec_flate.cpp b/core/fxcodec/codec/fx_codec_flate.cpp
index 49a4f34166..27416f1c67 100644
--- a/core/fxcodec/codec/fx_codec_flate.cpp
+++ b/core/fxcodec/codec/fx_codec_flate.cpp
@@ -147,7 +147,7 @@ int CLZWDecoder::Decode(uint8_t* dest_buf,
   m_Early = bEarlyChange ? 1 : 0;
   m_nCodes = 0;
   FX_DWORD old_code = (FX_DWORD)-1;
-  uint8_t last_char;
+  uint8_t last_char = 0;
   while (1) {
     if (m_InPos + m_CodeLen > src_size * 8) {
       break;
@@ -942,7 +942,7 @@ FX_DWORD CCodec_FlateModule::FlateOrLZWDecode(FX_BOOL bLZW,
       offset = src_size;
       int err = decoder->Decode(NULL, dest_size, src_buf, offset, bEarlyChange);
       if (err || dest_size == 0 || dest_size + 1 < dest_size) {
-        return -1;
+        return static_cast<FX_DWORD>(-1);
       }
     }
     {
@@ -965,7 +965,7 @@ FX_DWORD CCodec_FlateModule::FlateOrLZWDecode(FX_BOOL bLZW,
     ret =
         TIFF_Predictor(dest_buf, dest_size, Colors, BitsPerComponent, Columns);
   }
-  return ret ? offset : -1;
+  return ret ? offset : static_cast<FX_DWORD>(-1);
 }
 FX_BOOL CCodec_FlateModule::Encode(const uint8_t* src_buf,
                                    FX_DWORD src_size,
diff --git a/core/fxcodec/codec/fx_codec_jpx_opj.cpp b/core/fxcodec/codec/fx_codec_jpx_opj.cpp
index aaa89388b8..a57b93df22 100644
--- a/core/fxcodec/codec/fx_codec_jpx_opj.cpp
+++ b/core/fxcodec/codec/fx_codec_jpx_opj.cpp
@@ -24,16 +24,17 @@ static void fx_warning_callback(const char* msg, void* client_data) {
 static void fx_info_callback(const char* msg, void* client_data) {
   (void)client_data;
 }
+
 OPJ_SIZE_T opj_read_from_memory(void* p_buffer,
                                 OPJ_SIZE_T nb_bytes,
                                 void* p_user_data) {
   DecodeData* srcData = static_cast<DecodeData*>(p_user_data);
   if (!srcData || !srcData->src_data || srcData->src_size == 0) {
-    return -1;
+    return static_cast<OPJ_SIZE_T>(-1);
   }
   // Reads at EOF return an error code.
   if (srcData->offset >= srcData->src_size) {
-    return -1;
+    return static_cast<OPJ_SIZE_T>(-1);
   }
   OPJ_SIZE_T bufferLength = srcData->src_size - srcData->offset;
   OPJ_SIZE_T readlength = nb_bytes < bufferLength ? nb_bytes : bufferLength;
@@ -41,16 +42,17 @@ OPJ_SIZE_T opj_read_from_memory(void* p_buffer,
   srcData->offset += readlength;
   return readlength;
 }
+
 OPJ_SIZE_T opj_write_from_memory(void* p_buffer,
                                  OPJ_SIZE_T nb_bytes,
                                  void* p_user_data) {
   DecodeData* srcData = static_cast<DecodeData*>(p_user_data);
   if (!srcData || !srcData->src_data || srcData->src_size == 0) {
-    return -1;
+    return static_cast<OPJ_SIZE_T>(-1);
   }
   // Writes at EOF return an error code.
   if (srcData->offset >= srcData->src_size) {
-    return -1;
+    return static_cast<OPJ_SIZE_T>(-1);
   }
   OPJ_SIZE_T bufferLength = srcData->src_size - srcData->offset;
   OPJ_SIZE_T writeLength = nb_bytes < bufferLength ? nb_bytes : bufferLength;
@@ -58,17 +60,18 @@ OPJ_SIZE_T opj_write_from_memory(void* p_buffer,
   srcData->offset += writeLength;
   return writeLength;
 }
+
 OPJ_OFF_T opj_skip_from_memory(OPJ_OFF_T nb_bytes, void* p_user_data) {
   DecodeData* srcData = static_cast<DecodeData*>(p_user_data);
   if (!srcData || !srcData->src_data || srcData->src_size == 0) {
-    return -1;
+    return static_cast<OPJ_OFF_T>(-1);
   }
   // Offsets are signed and may indicate a negative skip. Do not support this
   // because of the strange return convention where either bytes skipped or
   // -1 is returned. Following that convention, a successful relative seek of
   // -1 bytes would be required to to give the same result as the error case.
   if (nb_bytes < 0) {
-    return -1;
+    return static_cast<OPJ_OFF_T>(-1);
   }
   // FIXME: use std::make_unsigned<OPJ_OFF_T>::type once c++11 lib is OK'd.
   uint64_t unsignedNbBytes = static_cast<uint64_t>(nb_bytes);
@@ -89,6 +92,7 @@ OPJ_OFF_T opj_skip_from_memory(OPJ_OFF_T nb_bytes, void* p_user_data) {
   }
   return nb_bytes;
 }
+
 OPJ_BOOL opj_seek_from_memory(OPJ_OFF_T nb_bytes, void* p_user_data) {
   DecodeData* srcData = static_cast<DecodeData*>(p_user_data);
   if (!srcData || !srcData->src_data || srcData->src_size == 0) {
diff --git a/core/fxcodec/codec/fx_codec_tiff.cpp b/core/fxcodec/codec/fx_codec_tiff.cpp
index 2af92f2f12..0312622fb4 100644
--- a/core/fxcodec/codec/fx_codec_tiff.cpp
+++ b/core/fxcodec/codec/fx_codec_tiff.cpp
@@ -122,20 +122,20 @@ static toff_t _tiff_seek(thandle_t context, toff_t offset, int whence) {
     case 2:
       if (pTiffContext->isDecoder) {
         if (pTiffContext->io.in->GetSize() < (FX_FILESIZE)offset) {
-          return -1;
+          return static_cast<toff_t>(-1);
         }
         pTiffContext->offset =
             (FX_DWORD)(pTiffContext->io.in->GetSize() - offset);
       } else {
         if (pTiffContext->io.out->GetSize() < (FX_FILESIZE)offset) {
-          return -1;
+          return static_cast<toff_t>(-1);
         }
         pTiffContext->offset =
             (FX_DWORD)(pTiffContext->io.out->GetSize() - offset);
       }
       break;
     default:
-      return -1;
+      return static_cast<toff_t>(-1);
   }
   ASSERT(pTiffContext->isDecoder ? (pTiffContext->offset <=
                                     (FX_DWORD)pTiffContext->io.in->GetSize())