PVS-Studio warning V579 for Doom3

void idMegaTexture::GenerateMegaMipMaps() {
  ...
  byte *newBlock = (byte *)_alloca( tileSize );
  ...
  memset( newBlock, 0, sizeof( newBlock ) );
  ...
}

Most likely this is what should be written here: memset( newBlock, 0, tileSize );

This suspicious code was found in Doom3 project by PVS-Studio static code analyzer.
Warning message is:
V579 The memset function receives the pointer and its size as arguments. It is possibly a mistake. Inspect the third argument. DoomDLL megatexture.cpp 542

PVS-Studio is a static analyzer for detecting bugs in the source code of applications written in C, C++, C++11, C++/CX. Site: http://www.viva64.com/en/pvs-studio/