Compilation issue on Mingw32: redeclared without dllimport attribute

[nddrylliog]

Here's the log:

$ ./configure --prefix=/usr/local --with-libzmq=/usr/local
$ make
*snip*
make[2]: Entering directory `/g/Dev/czmq-1.3.1/src'
/bin/sh ../libtool --tag=CC   --mode=compile gcc -std=gnu99 -DHAVE_CONFIG_H -I. -I../include  -Werror -Wall -D_REENTRANT -D_THREAD_SAFE   -I/usr/local/include -g -O2 -MT zclock.lo -MD -MP -MF .deps/zclock.Tpo -c -o zclock.lo zclock.c
libtool: compile:  gcc -std=gnu99 -DHAVE_CONFIG_H -I. -I../include -Werror -Wall -D_REENTRANT -D_THREAD_SAFE -I/usr/local/include -g -O2 -MT zclock.lo -MD -MP -MF .deps/zclock.Tpo -c zclock.c  -DDLL_EXPORT -DPIC -o .libs/zclock.o
libtool: compile:  gcc -std=gnu99 -DHAVE_CONFIG_H -I. -I../include -Werror -Wall -D_REENTRANT -D_THREAD_SAFE -I/usr/local/include -g -O2 -MT zclock.lo -MD -MP -MF .deps/zclock.Tpo -c zclock.c -o zclock.o >/dev/null 2>&1
make[2]: *** [zclock.lo] Error 1

Upon running the same gcc command by hand, I get these error messages:

zclock.c:70:1: error: 'zclock_sleep' redeclared without dllimport attribute: previous dllimport ignored [-Werror=attributes]
zclock.c:97:1: error: 'zclock_time' redeclared without dllimport attribute: previous dllimport ignored [-Werror=attributes]
zclock.c:117:1: error: 'zclock_log' redeclared without dllimport attribute: previous dllimport ignored [-Werror=attributes]
cc1.exe: all warnings being treated as errors

I don't know how harmful that warning is (never really built DLLs on Windows myself), but with -Werror it does cause the build to fail.

As for my setup, here it is:

• GCC 4.7.2, 32-bit
• autotools 2.68
• GNU m4 1.4.14

That's building czmq 1.3.2, fresh out the release cutter :)

[pijyoi]

How about if you configure --disable-static?

Update: I have tried
./configure --with-libzmq=/usr/local --disable-static
and the compilation of the dynamic library works but not for czmq_selftest.exe

The problem is that the *_test() functions called by czmq_selftest.c are not exported in the DLL.
I am not sure exporting the *_test() functions is the right thing to do either.

[ghost]

Could you please try again with the latest czmq and zmq? Or could
someone tell me the build process for cross compiling with mingw32?

[pijyoi]

I use the toolchain from http://mxe.cc and I create a folder $HOME/local_mingw32.

for libzmq:
CPPFLAGS=-DFD_SETSIZE=1024 ./configure --host=i686-pc-mingw32 --with-libsodium=$HOME/local_mingw32 --prefix=$HOME/local_mingw32

for czmq
./configure --host=i686-pc-mingw32 --with-libzmq=$HOME/local_mingw32 --prefix=$HOME/local_mingw32

Sometimes, there are changes in the source code that break compilation with MinGW32.
Mostly they arise from conflating "Windows platform" with "MSVC compiler".

[ulikoehler]

I think we need some kind of guide how to get MinGW+(C)ZMQ build working under wine, because the errors seem to occur somewhat frequently and it seems like most people (including me and Travis) are using pretty much Linux-only throughout the development process.

[ghost]

I'll test it now thanks @pijyoi

@ulikoehler if no one else wants to write it then I'll be happy to
whenever I'm free (I'm almost always free). Also I have a dual boot
setup with Windows 7 so I'll reboot into that once a week or so just to
make sure nothing is broken.

[hintjens]

@shancat regular builds on Windows would be awesome...

[ghost]

@pijyoi which packages will I need? At the moment I'm running make gcc
but is there anything else I'll need before compiling
libsodium/zmq/czmq?

@hintjens I'll get started ASAP then :)

[hintjens]

@shancat neat... :)

[pijyoi]

No other package is needed. You just need to build the cross compiler.

[ulikoehler]

I can see two different approaches here:

• Cross-Compiling
• Running the compiler in wine

The first one would obviously be easier but I'm not entirely sure if it doesn't act different if run (pseudo-)natively on Windows/Wine -- In the past I've had some problems cross-compiling ARMv6L packages for the Raspberry Pi. I didn't really try to track it down, but at least in this case, the native-approach did a better job.

Do you have experience with mingw crosscompiling?

[ghost]

I have no experience crosscompiling or with Wine but I'm happy to learn.
I think we should, at the very least, incorporate a MinGW build into
the autobuild. I'm sure I've seen other projects do this so it shouldn't
be too hard.

Baby-steps, we'll see how that goes and if something crops up regarding
MinGW we'll see what we can do regarding Wine. Sound like a plan?

[ulikoehler]

Absolutely :)

[ghost]

@pijyoi finally finished downloading gcc. Did you do anything special
for libsodium?

[pijyoi]

Libsodium builds cleanly with no changes. Just set prefix to local_mingw
like the rest. I believe the win32 binary distributed by libsodium is cross
compiled.

FWIW, czmq_selftest.exe runs without errors under wine. Lots of failures
for the zmq tests though. A lot of them are bind failures due to closing
and rebinding to the same port.

[hintjens]

No progress on this; closing it.