ncplot @2020-02-21_1: Overlinking

[Dave-Allured (Dave Allured)]

Please remove port:zlib from depends_lib. This is only an indirect dependency through port netcdf. Also remove -lz from the makefile patch. Thanks.

[mf2k (Frank Schima)]

I don't understand this request. Currently 990 ports depend on zlib, so this is hardly uncommon. Also, the Makefile is from upstream. Why should that change?

I added the dependency on it because otool -L shows it as linking directly with it.

$ otool -L /opt/local/bin/ncplot
/opt/local/bin/ncplot:
	/opt/local/lib/libXm.4.dylib (compatibility version 5.0.0, current version 5.4.0)
	/opt/local/lib/libXt.6.dylib (compatibility version 7.0.0, current version 7.0.0)
	/opt/local/lib/libX11.6.dylib (compatibility version 10.0.0, current version 10.0.0)
	/opt/local/lib/libnetcdf.18.dylib (compatibility version 18.0.0, current version 18.0.0)
	/opt/local/lib/libgsl.25.dylib (compatibility version 26.0.0, current version 26.0.0)
	/usr/lib/libSystem.B.dylib (compatibility version 1.0.0, current version 1281.100.1)
	/opt/local/lib/libpng16.16.dylib (compatibility version 54.0.0, current version 54.0.0)
	/opt/local/lib/libz.1.dylib (compatibility version 1.0.0, current version 1.2.11)
	/usr/lib/libc++.1.dylib (compatibility version 1.0.0, current version 902.1.0)

[Dave-Allured (Dave Allured)]

That Makefile appeared to be somewhat old and unrefined, so I was suspicious. I checked the code two different ways for zlib dependency. I could not find any recognizable references to zlib headers or functions. Also I tried omitting -lz from the link command, and that gave a working executable with no complaints.

I suspect that in your case, -lz was in your linker formula via the makefile patch, before checking the result with otool. My guess is that this forces /opt/local/lib/libz.*.dylib to be visible, regardless of whether the application actually has any direct reference. You might try omitting -lz and see if you get a good executable.

My test setup is a little different than yours. I am working with a down level Macports setup, thanks in part to Covid. I am compiling ncplot stand-alone rather than with port install. I do not see how any of that would make a difference for this particular dependency, but I suppose it is possible.

~/3rd/ncplot/0725 32> otool -L ncplot
ncplot:
  /opt/local/lib/libXm.4.dylib (compatibility version 5.0.0, current version 5.4.0)
  /opt/local/lib/libXt.6.dylib (compatibility version 7.0.0, current version 7.0.0)
  /opt/local/lib/libX11.6.dylib (compatibility version 10.0.0, current version 10.0.0)
  /opt/local/lib/libnetcdf.15.dylib (compatibility version 15.0.0, current version 15.0.0)
  /opt/local/lib/libgsl.23.dylib (compatibility version 25.0.0, current version 25.0.0)
  /opt/local/lib/libpng16.16.dylib (compatibility version 53.0.0, current version 53.0.0)
  /opt/local/lib/libgcc/libstdc++.6.dylib (compatibility version 7.0.0, current version 7.25.0)
  /usr/lib/libSystem.B.dylib (compatibility version 1.0.0, current version 1252.250.1)
  /opt/local/lib/libgcc/libgcc_s.1.dylib (compatibility version 1.0.0, current version 1.0.0)

[mf2k (Frank Schima)]

Yes, the Makefile is very primitive. You have to uncomment for a MacOS install, hence the patch. That's where the -lz comes from. If you happen to be in contact with the upstream developer, who works for NCAR, maybe you can ask him about it?

[Dave-Allured (Dave Allured)]

Question filed upstream: ​https://github.com/NCAR/ncplot/issues/5

[Dave-Allured (Dave Allured)]

The reply was: "zlib was originally included because libpng required it. -lm and -lz removed." Please see the above reference for full context.

The upstream Makefile was updated. For Macports, I assume that zlib would be an indirect dependency through any version of libpng that needed it. Therefore I believe zlib should be removed as a direct dependency of ncplot.

Best practice for -lm is a mystery to me. There certainly are tons of math calls within ncplot.

[mf2k (Frank Schima)]

Great, thank you. I have updated the port. I will wait a bit before committing to see if I can get it to use gmt first.

[mf2k (Frank Schima)]

In 11cf22e462478e7b8675bc6e498aa7593c3f6b3e/macports-ports (master):

ncplot: Update to version 2020-07-28

• Remove zlib dependency

Fixes: #60904