fwrite fails to write 9.999999999999998

[tbetz]

I tried to write a data.table to a file with fwrite, and noticed that the value of one column is not written.

dt <- data.table(V1=c(1), V2=c(9.9999999999999982236431605997495353221893310546875))
fwrite(dt, file="test.txt", sep=";")

The output file looks like this:
V1;V2
1

I expected it to look like this:
V1;V2
1;10

If I revert the column order, calling fwrite crashes my R session.

dt <- data.table(V2=c(9.9999999999999982236431605997495353221893310546875), V1=c(1))
fwrite(dt, file="test.txt", sep=";") # this causes R to crash

The details for the crash are (sorry about the German output, not sure how to change that to English):
Problemsignatur:
Problemereignisname: APPCRASH
Anwendungsname: rsession.exe
Anwendungsversion: 0.99.903.0
Anwendungszeitstempel: 00000000
Fehlermodulname: ntdll.dll
Fehlermodulversion: 6.1.7601.23455
Fehlermodulzeitstempel: 573a54b7
Ausnahmecode: c0000005
Ausnahmeoffset: 000000000004e27c
Betriebsystemversion: 6.1.7601.2.1.0.256.48
Gebietsschema-ID: 1031
Zusatzinformation 1: 1ef2
Zusatzinformation 2: 1ef2a2536739df668f2a666c3c230c35
Zusatzinformation 3: 6c5c
Zusatzinformation 4: 6c5c2328a6b86468f828af8fe0e531ef

My session info is as follows:
R version 3.3.1 (2016-06-21)
Platform: x86_64-w64-mingw32/x64 (64-bit)
Running under: Windows 7 x64 (build 7601) Service Pack 1

locale:
[1] LC_COLLATE=German_Germany.1252 LC_CTYPE=German_Germany.1252 LC_MONETARY=German_Germany.1252 LC_NUMERIC=C
[5] LC_TIME=German_Germany.1252

attached base packages:
[1] stats graphics grDevices utils datasets methods base

other attached packages:
[1] data.table_1.9.7

loaded via a namespace (and not attached):
[1] tools_3.3.1

data.table 1.9.7 IN DEVELOPMENT built 2016-09-11 14:38:19 UTC; travis