This little program tells you the size of size_t and void*
On Linux, just run gcc on your platform:
gcc -o checkbitsize checkBitSize.c
Some examples for cross-compiling:
arm: arm-linux-gnueabihf-gcc -o checkbitsize checkBitSize.c
i386: gcc -m32 -o checkbitsize checkBitSize.c
For MSVC, the targets Win32 and x64 are provided in the solution file. Examples:
/path/to/MSBuild.exe build/MSVC/checkBitSize.sln //t:Rebuild //p:Configuration=Release //p:Platform=Win32
/path/to/MSBuild.exe build/MSVC/checkBitSize.sln //t:Rebuild //p:Configuration=Release //p:Platform=x64