Kill off some memset()s following FX_Alloc()

Change-Id: I92aa74c86aef890fcb991f039b9707d680fdb83c
Reviewed-on: https://pdfium-review.googlesource.com/c/43652
Reviewed-by: Lei Zhang <thestig@chromium.org>
Commit-Queue: Tom Sepez <tsepez@chromium.org>

core/fxcodec/codec/ccodec_progressivedecoder.cpp

diff --git a/core/fxcodec/codec/ccodec_progressivedecoder.cpp b/core/fxcodec/codec/ccodec_progressivedecoder.cpp
index 27a2494..0e60145 100644
--- a/core/fxcodec/codec/ccodec_progressivedecoder.cpp
+++ b/core/fxcodec/codec/ccodec_progressivedecoder.cpp
@@ -805,7 +805,6 @@
   GetTransMethod(m_pDeviceBitmap->GetFormat(), m_SrcFormat);
   m_ScanlineSize = FxAlignToBoundary<4>(m_SrcWidth * m_SrcComponents);
   m_pDecodeBuf.reset(FX_Alloc(uint8_t, m_ScanlineSize));
-  memset(m_pDecodeBuf.get(), 0, m_ScanlineSize);
   m_WeightHorz.Calc(m_sizeX, 0, m_sizeX, m_clipBox.Width(), 0,
                     m_clipBox.Width());
   m_WeightVert.Calc(m_sizeY, m_clipBox.Height());
@@ -903,7 +902,6 @@
   GetTransMethod(m_pDeviceBitmap->GetFormat(), m_SrcFormat);
   int scanline_size = FxAlignToBoundary<4>(m_SrcWidth);
   m_pDecodeBuf.reset(FX_Alloc(uint8_t, scanline_size));
-  memset(m_pDecodeBuf.get(), 0, scanline_size);
   m_WeightHorz.Calc(m_sizeX, 0, m_sizeX, m_clipBox.Width(), 0,
                     m_clipBox.Width());
   m_WeightVert.Calc(m_sizeY, m_clipBox.Height());
@@ -1110,7 +1108,6 @@
   int scanline_size = (m_SrcWidth + down_scale - 1) / down_scale;
   scanline_size = FxAlignToBoundary<4>(scanline_size * m_SrcComponents);
   m_pDecodeBuf.reset(FX_Alloc(uint8_t, scanline_size));
-  memset(m_pDecodeBuf.get(), 0, scanline_size);
   m_WeightHorz.Calc(m_sizeX, 0, m_sizeX, m_clipBox.Width(), 0,
                     m_clipBox.Width());
   m_WeightVert.Calc(m_sizeY, m_clipBox.Height());
@@ -1272,7 +1269,6 @@
     }
     if (m_pSrcBuf && input_size > m_SrcSize) {
       m_pSrcBuf.reset(FX_Alloc(uint8_t, input_size));
-      memset(m_pSrcBuf.get(), 0, input_size);
       m_SrcSize = input_size;
     }
     bResult = m_pFile->ReadBlock(m_pSrcBuf.get(), m_offSet, input_size);
@@ -1334,7 +1330,6 @@
   GetTransMethod(m_pDeviceBitmap->GetFormat(), m_SrcFormat);
   int scanline_size = FxAlignToBoundary<4>(m_SrcWidth * m_SrcComponents);
   m_pDecodeBuf.reset(FX_Alloc(uint8_t, scanline_size));
-  memset(m_pDecodeBuf.get(), 0, scanline_size);
   m_WeightHorzOO.Calc(m_sizeX, m_clipBox.Width());
   m_WeightVert.Calc(m_sizeY, m_clipBox.Height());
   m_status = FXCODEC_STATUS_DECODE_TOBECONTINUE;
@@ -1360,7 +1355,6 @@
     }
     if (m_pSrcBuf && input_size > m_SrcSize) {
       m_pSrcBuf.reset(FX_Alloc(uint8_t, input_size));
-      memset(m_pSrcBuf.get(), 0, input_size);
       m_SrcSize = input_size;
     }
     bool bResult = m_pFile->ReadBlock(m_pSrcBuf.get(), m_offSet, input_size);

core/fxcodec/jbig2/JBig2_Context.cpp

diff --git a/core/fxcodec/jbig2/JBig2_Context.cpp b/core/fxcodec/jbig2/JBig2_Context.cpp
index 4656bfa..3a868c1 100644
--- a/core/fxcodec/jbig2/JBig2_Context.cpp
+++ b/core/fxcodec/jbig2/JBig2_Context.cpp
@@ -817,7 +817,6 @@
   if (pTRD->SBREFINE == 1) {
     const size_t size = GetRefAggContextSize(pTRD->SBRTEMPLATE);
     grContext.reset(FX_Alloc(JBig2ArithCtx, size));
-    memset(grContext.get(), 0, sizeof(JBig2ArithCtx) * size);
   }
   if (pTRD->SBHUFF == 0) {
     auto pArithDecoder =
@@ -871,7 +870,6 @@
     const size_t size = GetHuffContextSize(pPDD->HDTEMPLATE);
     std::unique_ptr<JBig2ArithCtx, FxFreeDeleter> gbContext(
         FX_Alloc(JBig2ArithCtx, size));
-    memset(gbContext.get(), 0, sizeof(JBig2ArithCtx) * size);
     auto pArithDecoder =
         pdfium::MakeUnique<CJBig2_ArithDecoder>(m_pStream.get());
     pSegment->m_PatternDict =
@@ -940,7 +938,6 @@
     const size_t size = GetHuffContextSize(pHRD->HTEMPLATE);
     std::unique_ptr<JBig2ArithCtx, FxFreeDeleter> gbContext(
         FX_Alloc(JBig2ArithCtx, size));
-    memset(gbContext.get(), 0, sizeof(JBig2ArithCtx) * size);
     auto pArithDecoder =
         pdfium::MakeUnique<CJBig2_ArithDecoder>(m_pStream.get());
     pSegment->m_Image =
@@ -1123,7 +1120,6 @@
   const size_t size = GetRefAggContextSize(pGRRD->GRTEMPLATE);
   std::unique_ptr<JBig2ArithCtx, FxFreeDeleter> grContext(
       FX_Alloc(JBig2ArithCtx, size));
-  memset(grContext.get(), 0, sizeof(JBig2ArithCtx) * size);
   auto pArithDecoder = pdfium::MakeUnique<CJBig2_ArithDecoder>(m_pStream.get());
   pSegment->m_nResultType = JBIG2_IMAGE_POINTER;
   pSegment->m_Image = pGRRD->Decode(pArithDecoder.get(), grContext.get());

core/fxcrt/fx_memory.h

diff --git a/core/fxcrt/fx_memory.h b/core/fxcrt/fx_memory.h
index b399112..5596bce 100644
--- a/core/fxcrt/fx_memory.h
+++ b/core/fxcrt/fx_memory.h
@@ -88,7 +88,7 @@
   return result;
 }
 
-// These never return nullptr.
+// These never return nullptr, and must return cleared memory.
 #define FX_Alloc(type, size) \
   static_cast<type*>(FX_AllocOrDie(size, sizeof(type)))
 #define FX_Alloc2D(type, w, h) \
@@ -96,7 +96,7 @@
 #define FX_Realloc(type, ptr, size) \
   static_cast<type*>(FX_ReallocOrDie(ptr, size, sizeof(type)))
 
-// May return nullptr.
+// May return nullptr, but returns cleared memory otherwise.
 #define FX_TryAlloc(type, size) \
   static_cast<type*>(FX_SafeAlloc(size, sizeof(type)))
 #define FX_TryRealloc(type, ptr, size) \

fxbarcode/datamatrix/BC_ErrorCorrection.cpp

diff --git a/fxbarcode/datamatrix/BC_ErrorCorrection.cpp b/fxbarcode/datamatrix/BC_ErrorCorrection.cpp
index 8344264..87dc5f6 100644
--- a/fxbarcode/datamatrix/BC_ErrorCorrection.cpp
+++ b/fxbarcode/datamatrix/BC_ErrorCorrection.cpp
@@ -184,7 +184,6 @@
     return WideString();
   }
   uint16_t* ecc = FX_Alloc(uint16_t, numECWords);
-  memset(ecc, 0, numECWords * sizeof(uint16_t));
   for (int32_t l = start; l < start + len; l++) {
     uint16_t m = ecc[numECWords - 1] ^ codewords[l];
     for (int32_t k = numECWords - 1; k > 0; k--) {