$ sudo cpanm Crypt::Curve25519
--> Working on Crypt::Curve25519
Fetching http://www.cpan.org/authors/id/A/AJ/AJGB/Crypt-Curve25519-0.06.tar.gz ... OK
Configuring Crypt-Curve25519-0.06 ... OK
Building and testing Crypt-Curve25519-0.06 ... FAIL
! Installing Crypt::Curve25519 failed. See /home/tinyos/.cpanm/work/1557136045.12229/build.log for details. Retry with --force to force install it.

##</code><code>##

$ cat /home/tinyos/.cpanm/work/1557136045.12229/build.log
cpanm (App::cpanminus) 1.7044 on perl 5.026002 built for x86_64-linux-gnu-thread-multi
Work directory is /home/tinyos/.cpanm/work/1557136045.12229
You have make /usr/bin/make
You have LWP 6.35
You have /bin/tar: tar (GNU tar) 1.30
Copyright (C) 2017 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>.
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.

Written by John Gilmore and Jay Fenlason.
You have /usr/bin/unzip
Searching Crypt::Curve25519 () on cpanmetadb ...
--> Working on Crypt::Curve25519
Fetching http://www.cpan.org/authors/id/A/AJ/AJGB/Crypt-Curve25519-0.06.tar.gz
-> OK
Unpacking Crypt-Curve25519-0.06.tar.gz
Entering Crypt-Curve25519-0.06
Checking configure dependencies from META.json
Configuring Crypt-Curve25519-0.06
Running Makefile.PL
Checking if your kit is complete...
Looks good
Generating a Unix-style Makefile
Writing Makefile for Crypt::Curve25519
Writing MYMETA.yml and MYMETA.json
-> OK
Checking dependencies from MYMETA.json ...
Checking if you have File::Spec 0 ... Yes (3.75)
Checking if you have Test::More 0 ... Yes (1.302164)
Checking if you have IPC::Open3 0 ... Yes (1.20)
Checking if you have ExtUtils::MakeMaker 0 ... Yes (7.34)
Checking if you have IO::Handle 0 ... Yes (1.36)
Building and testing Crypt-Curve25519-0.06
cp lib/Crypt/Curve25519.pm blib/lib/Crypt/Curve25519.pm
Running Mkbootstrap for Curve25519 ()
chmod 644 "Curve25519.bs"
"/usr/bin/perl" -MExtUtils::Command::MM -e 'cp_nonempty' -- Curve25519.bs blib/arch/auto/Crypt/Curve25519/Curve25519.bs 644
"/usr/bin/perl" "/usr/share/perl/5.26/ExtUtils/xsubpp"  -typemap '/usr/share/perl/5.26/ExtUtils/typemap' -typemap '/home/tinyos/.cpanm/work/1557136045.12229/Crypt-Curve25519-0.06/typemap'  Curve25519.xs > Curve25519.xsc
mv Curve25519.xsc Curve25519.c
x86_64-linux-gnu-gcc -c   -D_REENTRANT -D_GNU_SOURCE -DDEBIAN -fwrapv -fno-strict-aliasing -pipe -I/usr/local/include -D_LARGEFILE_SOURCE -D_FILE_OFFSET_BITS=64 -O2 -g   -DVERSION=\"0.06\" -DXS_VERSION=\"0.06\" -fPIC "-I/usr/lib/x86_64-linux-gnu/perl/5.26/CORE"  -DUSE_X64=1 Curve25519.c
In file included from Curve25519.xs:7:
curve25519-donna-c64.c:99:1: error: conflicting types for ‘fmul’
 fmul(felem output, const felem in2, const felem in) {
 ^~~~
In file included from /usr/lib/x86_64-linux-gnu/perl/5.26/CORE/perl.h:2118,
                 from Curve25519.xs:3:
/usr/include/x86_64-linux-gnu/bits/mathcalls-narrow.h:30:20: note: previous declaration of ‘fmul’ was here
 __MATHCALL_NARROW (__MATHCALL_NAME (mul), __MATHCALL_REDIR_NAME (mul), 2);
                    ^~~~~~~~~~~~~~~
make: *** [Makefile:335: Curve25519.o] Error 1
-> FAIL Installing Crypt::Curve25519 failed. See /home/tinyos/.cpanm/work/1557136045.12229/build.log for details. Retry with --force to force install it.