title: Rcpp compilation on windows fails (64bit)
body: <p>I am trying to set up Rcpp on my Windows machine (have not had issues on my unix box).</p>
  
  <p>I have installed R in C:/opt/R/current (a Google search suggested that spaces in installation paths could give trouble), and I have installed Rtools.
  I have the simple cpp file:</p>
  
  <pre><code>#include &lt;Rcpp.h&gt;
  using namespace Rcpp;
  
  // [[Rcpp::export]]
  int timesTwo(int x) {
     return x * 2;
  }
  </code></pre>
  
  <p>and an R file:</p>
  
  <pre><code>library(Rcpp)
  sourceCpp("cppfile.cpp")
  </code></pre>
  
  <p>I get the following error:</p>
  
  <pre><code>C:/opt/R/current/etc/x64/Makeconf:196: warning: overriding recipe for target `.m.o' C:/opt/R/current/etc/x64/Makeconf:189: warning: ignoring old recipe for target `.m.o' C:\MINGW3~1\bin\make.exe: Interrupt/Exception caught (code = 0xc0000005, addr = 0x0x750343f9) Warning message: running command 'make -f "C:/opt/R/current/etc/x64/Makeconf" -f "C:/opt/R/current/share/make/winshlib.mk" SHLIB_LDFLAGS='$(SHLIB_CXXLDFLAGS)' SHLIB_LD='$(SHLIB_CXXLD)' SHLIB="sourceCpp_67515.dll" WIN=64 TCLBIN=64 OBJECTS="cppfile.o"' had status 255  
  Error in sourceCpp("cppfile.cpp") : 
    Error 1 occurred building shared library.
  </code></pre>
  
  <p>Any help would be appreciated.</p>
  
  <p>PS: Install e.g. <code>dplyr</code> from github via <code>devtools</code> works fine (and does quite a lot of compiling Rcpp stuff).</p>
  
  <p><strong>UPDATE</strong>: I added the Rtools bin dir to PATH, and now I get another error which seems to relate to 32/64bit:</p>
  
  <pre><code>g++ -m64 -I"C:/opt/R/current/include" -DNDEBUG     -I"C:/opt/R/current/library/Rcpp/include"  -I"d:/RCompile/CRANpkg/extralibs64/local/include"     -O2 -Wall  -mtune=core2 -c cppfile.cpp -o cppfile.o cppfile.cpp:1:0: sorry, unimplemented: 64-bit mode not compiled in make: *** [cppfile.o] Error 1 Warning message: running command 'make -f "C:/opt/R/current/etc/x64/Makeconf" -f "C:/opt/R/current/share/make/winshlib.mk" SHLIB_LDFLAGS='$(SHLIB_CXXLDFLAGS)' SHLIB_LD='$(SHLIB_CXXLD)' SHLIB="sourceCpp_41862.dll" WIN=64 TCLBIN=64 OBJECTS="cppfile.o"' had status 2  
  Error in sourceCpp("cppfile.cpp") : 
    Error 1 occurred building shared library.
  </code></pre>