dutf8.c:(.text+0x8): undefined reference to `_imp__nc_utf8proc_iterate'

[Reino17]

• What platform are you using? (please provide specific distribution/version in summary)
  • Windows
• 32 and/or 64 bit?
  • 32-bit
• What build system are you using?
  • autotools (configure) (gcc 4.9.4)
• Can you provide a sample netCDF file or C code to recreate the issue?
  • No

I'm using Roger's "ffmpeg-windows-build-helpers"-script to cross-compile FFMpeg with netCDF, but with an updated "build_netcdf"-function:

build_netcdf() {
  download_and_unpack_file https://github.com/Unidata/netcdf-c/archive/v4.4.1.1.tar.gz netcdf-c-4.4.1.1
  cd netcdf-c-4.4.1.1
    if [[ ! -f Makefile.in.bak ]]; then # Library only.
      sed -i.bak "/\tshare/s/share.*3 //" Makefile.in
    fi
    generic_configure "--disable-netcdf-4 --disable-dap --disable-examples --disable-utilities --disable-testsets"
    do_make_and_make_install
  cd ..
}

As you can see; v4.4.1.1 instead of v4.4.1. NetCDF is built without errors, as well as FFMpeg in the end.

When I however start using your Git-repository, then netCDF still builds without errors, but FFMpeg terminates with a fatal error:

build_netcdf() {
  do_git_checkout https://github.com/Unidata/netcdf-c.git
  cd netcdf-c_git
    apply_patch file://$patch_dir/netcdf-c_git_lib-only.diff
    generic_configure "--disable-netcdf-4 --disable-dap --disable-examples --disable-utilities --disable-testsets"
    do_make_and_make_install
  cd ..
}

...
LD      ffmpeg_g.exe
/cygdrive/d/ffmpeg-windows-build-helpers-master/native_build/windows/ffmpeg_local_builds/sand
box/cross_compilers/mingw-w64-i686/i686-w64-mingw32/lib/libnetcdf.a(libdispatch_la-dutf8.o):d
utf8.c:(.text+0x8): undefined reference to `_imp__nc_utf8proc_iterate'
collect2: error: ld returned 1 exit status
make: *** [Makefile:148: ffmpeg_g.exe] Error 1

I've done quite some searching for _imp__nc_utf8proc_iterate and if it's perhaps some library I'm missing, but Google returns practically nothing.
I have practically no experience with coding in C/C++, but in libdispatch/dutf8.c I can see nc_utf8proc_iterate being used, which (if I'm correct) is defined in libdispatch/utf8proc.h, so shouldn't it work?
Is this is real bug, or am I missing something?

---

'netcdf-c_git_lib-only.diff':

diff -ur libsrc/Makefile.am.bak libsrc/Makefile.am
--- libsrc/Makefile.am.bak	2017-04-28 17:28:44.062500000 +0200
+++ libsrc/Makefile.am	2017-04-28 17:55:23.468750000 +0200
@@ -42,28 +42,9 @@
 # These files are cleaned on developer workstations (and then rebuilt
 # with m4), but they are included in the distribution so that the user
 # does not have to have m4.
-MAINTAINERCLEANFILES = $(man_MANS) attrx.c ncx.c putgetx.c
-EXTRA_DIST = attr.m4 ncx.m4 putget.m4 $(man_MANS) CMakeLists.txt XGetopt.c
+MAINTAINERCLEANFILES = attrx.c ncx.c putgetx.c
+EXTRA_DIST = attr.m4 ncx.m4 putget.m4 CMakeLists.txt XGetopt.c
 
 # This tells make how to turn .m4 files into .c files.
 .m4.c:
 	m4 $(AM_M4FLAGS) $(M4FLAGS) -s $< > $@
-
-# The C API man page.
-man_MANS = netcdf.3
-
-# Decide what goes in the man page, based on user configure options.
-ARGS_MANPAGE = -DAPI=C
-if USE_NETCDF4
-ARGS_MANPAGE += -DNETCDF4=TRUE
-endif
-if BUILD_DAP
-ARGS_MANPAGE += -DDAP=TRUE
-endif
-if BUILD_PARALLEL
-ARGS_MANPAGE += -DPARALLEL_IO=TRUE
-endif
-
-# This rule generates the C manpage.
-netcdf.3: $(top_srcdir)/docs/netcdf.m4
-	m4 $(M4FLAGS) $(ARGS_MANPAGE) $? >$@  || rm $@

[WardF]

Interesting, I did not realize that ffmpeg had netcdf support. nc_utf8proc_iterate is a netCDF function, certainly. There isn't an obvious reason that I can see that this would be failing; let me take a look and see if I can recreate it.

[Reino17]

Last week FFmpeg has stopped using netCDF-C in favour of libmysofa. This issue has become superfluous as there's no need to solve it anymore, so I'm closing it now.
You're of course free to continue investigating this issue, but then you can only use versions of FFmpeg before FFmpeg/FFmpeg@2336c76.

[DennisHeimbigner]

I did some searching and found this:

https://stackoverflow.com/questions/5159353/how-can-i-get-rid-of-the-imp-prefix-in-the-linker-in-vc
It says:
The imp prefix appears whenever you are linking to a DLL. It does not appear when linking to
statically linked libraries. Most likely the code is generated to be linked against a DLL import lib,
but you have linked it with a static lib instead.
The prefix is added when you mark the imported function with __declspec(dllimport) - make sure
your imports are not using this when not linking against a DLL.
Still leaves questions unanswered, but closer to a solution.

[DennisHeimbigner]

This may have been fixed by pull request #430.
But since we cannot duplicate the failure, I am not quite sure. Closing for now.

[Reino17]

I've just tried to compile FFmpeg (https://github.com/FFmpeg/FFmpeg/tree/a32a6b4201dca46c54247194bd5249dfb7c64874, a version that still uses netCDF-C) with the latest netCDF-C version from git. Result; the same error-message:

LD      ffmpeg_g.exe
/cygdrive/m/ffmpeg-windows-build-helpers-master/native_build/windows/ffmpeg_local_builds/sand
box/cross_compilers/mingw-w64-i686/i686-w64-mingw32/lib/libnetcdf.a(libdispatch_la-dutf8.o):d
utf8.c:(.text+0x15): undefined reference to `_imp__nc_utf8proc_iterate'
collect2: error: ld returned 1 exit status
make: *** [Makefile:143: ffmpeg_g.exe] Error 1

[DennisHeimbigner]

Then I have no fix and no idea why it fails. It works for my Visual Studio. Sorry.