Errors after installing RTools twice!

Summary:

I followed the instructions to install R tools. I already had R (v 3.4.1) and R studio (v1.0.143) installed. I checked the box for 'PATH' as directed in installation instructions. I checked the path in R with the command Sys.getenv("PATH"), and the first couple items looked like " "C:\Program Files\R\R-3.4.1\bin\x64;C:\RBuildTools\3.4\bin;C:\RBuildTools\3.4\mingw_32\bin;C:\GTK\bin;C:\Program Files ...." which appears to look correct. However, when I run the function to check if the toolchain works, I get an error (below). I use C++ a lot for coding...so it's not that I don't have a c++ compiler.

Description:

I entered this after installing Rtools 3.4.1964. Rstan library was loaded.

fx <- inline::cxxfunction( signature(x = "integer", y = "numeric" ) , '
return ScalarReal( INTEGER(x)[0] * REAL(y)[0] ) ;
' )
fx( 2L, 5 ) # should be 10

Error in compileCode(f, code, language = language, verbose = verbose) :
Compilation ERROR, function(s)/method(s) not created! c:/Rtools/mingw_64/bin/g++: not found
make: *** [fileb6c71d233ce.o] Error 127
Warning message:
running command 'make -f "C:/PROGRA1/R/R-341.1/etc/x64/Makeconf" -f "C:/PROGRA1/R/R-341.1/share/make/winshlib.mk" SHLIB_LDFLAGS='$(SHLIB_CXXLDFLAGS)' SHLIB_LD='$(SHLIB_CXXLD)' SHLIB="fileb6c71d233ce.dll" WIN=64 TCLBIN=64 OBJECTS="fileb6c71d233ce.o"' had status 2
In addition: Warning message:
running command 'C:/PROGRA1/R/R-341.1/bin/x64/R CMD SHLIB fileb6c71d233ce.cpp 2> fileb6c71d233ce.cpp.err.txt' had status 1

fx( 2L, 5 ) # should be 10
Error in fx(2L, 5) : could not find function "fx"

Reproducible Steps:

See above.

Current Output:

fx <- inline::cxxfunction( signature(x = "integer", y = "numeric" ) , '
return ScalarReal( INTEGER(x)[0] * REAL(y)[0] ) ;
' )
fx( 2L, 5 ) # should be 10

Error in compileCode(f, code, language = language, verbose = verbose) :
Compilation ERROR, function(s)/method(s) not created! c:/Rtools/mingw_64/bin/g++: not found
make: *** [fileb6c71d233ce.o] Error 127
Warning message:
running command 'make -f "C:/PROGRA1/R/R-341.1/etc/x64/Makeconf" -f "C:/PROGRA1/R/R-341.1/share/make/winshlib.mk" SHLIB_LDFLAGS='$(SHLIB_CXXLDFLAGS)' SHLIB_LD='$(SHLIB_CXXLD)' SHLIB="fileb6c71d233ce.dll" WIN=64 TCLBIN=64 OBJECTS="fileb6c71d233ce.o"' had status 2
In addition: Warning message:
running command 'C:/PROGRA1/R/R-341.1/bin/x64/R CMD SHLIB fileb6c71d233ce.cpp 2> fileb6c71d233ce.cpp.err.txt' had status 1

fx( 2L, 5 ) # should be 10
Error in fx(2L, 5) : could not find function "fx"

Expected Output:

Not an error like this. Expected 10 as example states.

RStan Version:

2.16.2

R Version:

3.4.1 (2017-06-30)

Operating System:

Your operating system Windows 10

Start with the R CMD SHLIB command and the referenced R-3.4.1/etc/x64/Makeconf and share/make/winshlib.mk files to trace why c:/Rtools/mingw_64/bin/g++ is missing. Reproduce the inline::cxxfunction example and confirm that it completes and fx(2L, 5) returns 10.