tweetnacl.c: broken compilation -pedantic and C++ comments (gcc-4.92)

[msune]

Issue description

Compilation with gcc/g++-4.9 configured as follows:

marc@Beluga:~/personal/msune/libzmq2/build$ ../configure --disable-drafts --enable-debug --disable-silent-rules

Is broken due to tweetnacl.c having C++-like comments:

marc@Beluga:~/personal/msune/libzmq2/build$ make
Making all in doc
make[1]: Entering directory '/home/marc/personal/msune/libzmq2/build/doc'
make[1]: Nothing to be done for 'all'.
make[1]: Leaving directory '/home/marc/personal/msune/libzmq2/build/doc'
make[1]: Entering directory '/home/marc/personal/msune/libzmq2/build'
/bin/bash ./libtool  --tag=CC   --mode=compile gcc -DHAVE_CONFIG_H -I. -I.. -I./src        -pedantic -Werror -Wall -D_GNU_SOURCE -D_REENTRANT -D_THREAD_SAFE -Wno-long-long -g -O0    -g -O0  -MT src/src_libzmq_la-tweetnacl.lo -MD -MP -MF src/.deps/src_libzmq_la-tweetnacl.Tpo -c -o src/src_libzmq_la-tweetnacl.lo `test -f 'src/tweetnacl.c' || echo '../'`src/tweetnacl.c
libtool: compile:  gcc -DHAVE_CONFIG_H -I. -I.. -I./src -pedantic -Werror -Wall -D_GNU_SOURCE -D_REENTRANT -D_THREAD_SAFE -Wno-long-long -g -O0 -g -O0 -MT src/src_libzmq_la-tweetnacl.lo -MD -MP -MF src/.deps/src_libzmq_la-tweetnacl.Tpo -c ../src/tweetnacl.c  -fPIC -DPIC -o src/.libs/src_libzmq_la-tweetnacl.o
../src/tweetnacl.c:49:1: error: C++ style comments are not allowed in ISO C90 [-Werror]
 // clang-format off
 ^
../src/tweetnacl.c:49:1: error: (this will be reported only once per input file) [-Werror]
In file included from ../src/tweetnacl.c:51:0:
../src/tweetnacl.h:55:1: error: C++ style comments are not allowed in ISO C90 [-Werror]
 //  Do not call manually! Use random_close from random.hpp
 ^
../src/tweetnacl.h:55:1: error: (this will be reported only once per input file) [-Werror]
cc1: all warnings being treated as errors
Makefile:3655: recipe for target 'src/src_libzmq_la-tweetnacl.lo' failed
make[1]: *** [src/src_libzmq_la-tweetnacl.lo] Error 1
make[1]: Leaving directory '/home/marc/personal/msune/libzmq2/build'
Makefile:4882: recipe for target 'all-recursive' failed
make: *** [all-recursive] Error 1
marc@Beluga:~/personal/msune/libzmq2/build$ ../configure --disable-drafts --enable-debug --disable-silent-rules 

Environment

• libzmq version 2aa54d662048f420ac0dbd5d9b46559963a675f2
• OS: Debian8

Minimal test code / Steps to reproduce the issue

1. Compile with:

marc@Beluga:~/personal/msune/libzmq2/build$ ../configure --disable-drafts --enable-debug --disable-silent-rules

[msune]

Suggested to disable (all) warnings on that (external?) file via pragma

[bluca]

I'll fix that, but since you are on Debian libzmq is already there - if you want newer versions you can add the repository:

https://software.opensuse.org/download.html?project=network%3Amessaging%3Azeromq%3Agit-stable&package=libzmq3-dev

[msune]

Just wanted to rise this.

I was just wanting to compile sources with no-drafts and enable-debug for #2742. I will fix comments for the moment.