title: Cannot install 'RCurl' (Rcurl.h:4:23: fatal error: curl/curl.h: No such file or directory)
body: <p>I've tried numerous methods to install RCurl, to no avail. I get this in my output:</p>
  
  <pre><code>    * installing *source* package 'RCurl' ...
  ** package 'RCurl' successfully unpacked and MD5 sums checked
  ** libs
  C:/Users/XXX/Documents/R/Rtools/mingw_64/bin/gcc  -I"C:/PROGRA~1/R/R-33~1.1/include" -DNDEBUG -I/include -DHAVE_LIBIDN_FIELD=1 -DHAVE_CURLOPT_URL=1 -DHAVE_CURLINFO_EFFECTIVE_URL=1 -DHAVE_CURLINFO_RESPONSE_CODE=1 -DHAVE_CURLINFO_TOTAL_TIME=1 -DHAVE_CURLINFO_NAMELOOKUP_TIME=1 -DHAVE_CURLINFO_CONNECT_TIME=1 -DHAVE_CURLINFO_PRETRANSFER_TIME=1 -DHAVE_CURLINFO_SIZE_UPLOAD=1 -DHAVE_CURLINFO_SIZE_DOWNLOAD=1 -DHAVE_CURLINFO_SPEED_DOWNLOAD=1 -DHAVE_CURLINFO_SPEED_UPLOAD=1 -DHAVE_CURLINFO_HEADER_SIZE=1 -DHAVE_CURLINFO_REQUEST_SIZE=1 -DHAVE_CURLINFO_SSL_VERIFYRESULT=1 -DHAVE_CURLINFO_FILETIME=1 -DHAVE_CURLINFO_CONTENT_LENGTH_DOWNLOAD=1 -DHAVE_CURLINFO_CONTENT_LENGTH_UPLOAD=1 -DHAVE_CURLINFO_STARTTRANSFER_TIME=1 -DHAVE_CURLINFO_CONTENT_TYPE=1 -DHAVE_CURLINFO_REDIRECT_TIME=1 -DHAVE_CURLINFO_REDIRECT_COUNT=1 -DHAVE_CURLINFO_PRIVATE=1 -DHAVE_CURLINFO_HTTP_CONNECTCODE=1 -DHAVE_CURLINFO_HTTPAUTH_AVAIL=1 -DHAVE_CURLINFO_PROXYAUTH_AVAIL=1 -DHAVE_CURLINFO_OS_ERRNO=1 -DHAVE_CURLINFO_NUM_CONNECTS=1 -DHAVE_CURLINFO_SSL_ENGINES=1 -DHAVE_CURLINFO_COOKIELIST=1 -DHAVE_CURLINFO_LASTSOCKET=1 -DHAVE_CURLINFO_FTP_ENTRY_PATH=1 -DHAVE_CURLINFO_REDIRECT_URL=1 -DHAVE_CURLINFO_PRIMARY_IP=1 -DHAVE_CURLINFO_APPCONNECT_TIME=1 -DHAVE_CURLINFO_CERTINFO=1 -DHAVE_CURLINFO_CONDITION_UNMET=1 -DHAVE_CURLOPT_KEYPASSWD=1 -DHAVE_CURLOPT_DIRLISTONLY=1 -DHAVE_CURLOPT_APPEND=1 -DHAVE_CURLOPT_KRBLEVEL=1 -DHAVE_CURLOPT_USE_SSL=1 -DHAVE_CURLOPT_TIMEOUT_MS=1 -DHAVE_CURLOPT_CONNECTTIMEOUT_MS=1 -DHAVE_CURLOPT_HTTP_TRANSFER_DECODING=1 -DHAVE_CURLOPT_HTTP_CONTENT_DECODING=1 -DHAVE_CURLOPT_NEW_FILE_PERMS=1 -DHAVE_CURLOPT_NEW_DIRECTORY_PERMS=1 -DHAVE_CURLOPT_POSTREDIR=1 -DHAVE_CURLOPT_OPENSOCKETFUNCTION=1 -DHAVE_CURLOPT_OPENSOCKETDATA=1 -DHAVE_CURLOPT_COPYPOSTFIELDS=1 -DHAVE_CURLOPT_PROXY_TRANSFER_MODE=1 -DHAVE_CURLOPT_SEEKFUNCTION=1 -DHAVE_CURLOPT_SEEKDATA=1 -DHAVE_CURLOPT_CRLFILE=1 -DHAVE_CURLOPT_ISSUERCERT=1 -DHAVE_CURLOPT_ADDRESS_SCOPE=1 -DHAVE_CURLOPT_CERTINFO=1 -DHAVE_CURLOPT_USERNAME=1 -DHAVE_CURLOPT_PASSWORD=1 -DHAVE_CURLOPT_PROXYUSERNAME=1 -DHAVE_CURLOPT_PROXYPASSWORD=1 -DHAVE_CURLOPT_SSH_HOST_PUBLIC_KEY_MD5=1 -DHAVE_CURLOPT_NOPROXY=1 -DHAVE_CURLOPT_TFTP_BLKSIZE=1 -DHAVE_CURLOPT_SOCKS5_GSSAPI_SERVICE=1 -DHAVE_CURLOPT_SOCKS5_GSSAPI_NEC=1 -DHAVE_CURLOPT_PROTOCOLS=1 -DHAVE_CURLOPT_REDIR_PROTOCOLS=1 -DHAVE_CURLOPT_SSH_AUTH_TYPES=1 -DHAVE_CURLOPT_SSH_PUBLIC_KEYFILE=1 -DHAVE_CURLOPT_SSH_PRIVATE_KEYFILE=1 -DHAVE_CURLOPT_FTP_SSL_CCC=1 -DHAVE_CURLOPT_COOKIELIST=1 -DHAVE_CURLOPT_IGNORE_CONTENT_LENGTH=1 -DHAVE_CURLOPT_FTP_SKIP_PASV_IP=1 -DHAVE_CURLOPT_FTP_FILEMETHOD=1 -DHAVE_CURLOPT_LOCALPORT=1 -DHAVE_CURLOPT_LOCALPORTRANGE=1 -DHAVE_CURLOPT_CONNECT_ONLY=1 -DHAVE_CURLOPT_CONV_FROM_NETWORK_FUNCTION=1 -DHAVE_CURLOPT_CONV_TO_NETWORK_FUNCTION=1 -DHAVE_CURLOPT_CONV_FROM_UTF8_FUNCTION=1 -DHAVE_CURLOPT_MAX_SEND_SPEED_LARGE=1 -DHAVE_CURLOPT_MAX_RECV_SPEED_LARGE=1 -DHAVE_CURLOPT_FTP_ALTERNATIVE_TO_USER=1 -DHAVE_CURLOPT_SOCKOPTFUNCTION=1 -DHAVE_CURLOPT_SOCKOPTDATA=1 -DHAVE_CURLOPT_SSL_SESSIONID_CACHE=1 -DHAVE_CURLOPT_WRITEDATA=1 -DCURL_STATICLIB    -I"d:/Compiler/gcc-4.9.3/local330/include"     -O2 -Wall  -std=gnu99 -mtune=core2 -c base64.c -o base64.o
  In file included from base64.c:1:0:
  Rcurl.h:4:23: fatal error: curl/curl.h: No such file or directory
   #include &lt;curl/curl.h&gt;
                         ^
  compilation terminated.
  make: *** [base64.o] Error 1
  Warning: running command 'make -f "Makevars.win" -f "C:/PROGRA~1/R/R-33~1.1/etc/x64/Makeconf" -f "C:/PROGRA~1/R/R-33~1.1/share/make/winshlib.mk" SHLIB="RCurl.dll" WIN=64 TCLBIN=64 OBJECTS="base64.o curl.o curlInit.o curl_base64.o enums.o json.o memoryManagement.o myUTF8.o"' had status 2
  ERROR: compilation failed for package 'RCurl'
  * removing 'C:/Users/XXX/Documents/R/win-library/3.3/RCurl'
  Warning in install.packages :
    running command '"C:/PROGRA~1/R/R-33~1.1/bin/x64/R" CMD INSTALL -l "C:\Users\XXX\Documents\R\win-library\3.3" C:\Users\XXX\AppData\Local\Temp\RtmpKOtnyD/downloaded_packages/RCurl_1.95-4.8.tar.gz' had status 1
  Warning in install.packages :
    installation of package ‘RCurl’ had non-zero exit status
  </code></pre>
  
  <p>I've successfully installed curl in Windows 10 ('curl_X64_ssl' version in C:curl) and got it running. I've also installed the 'curl' package in R, no problems there. I've tried adding this 'curl.h' file manually to both windows and R directories, but it didn't resolve the issue.
  Any other options?</p>