vtk @9.4.1: error: implicit declaration of function 'getentropy' is invalid in C99 [-Werror,-Wimplicit-function-declaration]

[ryandesign (Ryan Carsten Schmidt)]

​https://build.macports.org/builders/ports-11_x86_64-builder/builds/174902/steps/install-port/logs/stdio

ThirdParty/libxml2/vtklibxml2/dict.c:970:17: error: implicit declaration of function 'getentropy' is invalid in C99 [-Werror,-Wimplicit-function-declaration]
            if (getentropy(globalRngState, sizeof(globalRngState)) == 0)
                ^
1 error generated.

This appears to be happening when building a bundled copy of libxml2.

Here is the vtk bug report:

​https://gitlab.kitware.com/vtk/vtk/-/issues/19530

And the libxml2 bug report:

​https://gitlab.gnome.org/GNOME/libxml2/-/issues/820

I'll apply the fix to the libxml2 port. Maybe vtk can then use MacPorts libxml2 to avoid the need to build its own?

[ryandesign (Ryan Carsten Schmidt)]

Replying to ryandesign:

I'll apply the fix to the libxml2 port.

The problem doesn't apply to the libxml2 port because that uses the autotools build system whereas the problem is in the CMake build system.

[ryandesign (Ryan Carsten Schmidt)]

In fact the vtk port already has a patchfile (patch-libxml2-getentropy.diff) that looks related to this problem but it is only applied on Mac OS X 10.6 and earlier. I would guess that patch can be removed once the real fix is applied.

[Dave-Allured (Dave Allured)]

@barracuda156 was working on this getentropy problem, but did not get it to work for OS 10 and 11. See previous discussion in ​PR 26834. Perhaps improving the conditional for the OS version would work.

I am working on shifting away from VTK bundled libraries, toward MacPorts versions. Their build system is complicated and has stymied me so far.

[ryandesign (Ryan Carsten Schmidt)]

Replying to Dave-Allured:

Perhaps improving the conditional for the OS version would work.

According to the upstream bugs ​https://gitlab.gnome.org/GNOME/libxml2/-/commit/2617138d924e19211b530373162d93b8edc54eb8 should fix it. I have not tried it.

I am working on shifting away from VTK bundled libraries, toward MacPorts versions. Their build system is complicated and has stymied me so far.

I did not see a way to use MacPorts libxml2 instead of the bundled copy.

[Dave-Allured (Dave Allured)]

Documentation of VTK build controls is sparse and inconsistent. I think I found the correct control to use "external" MacPorts libxml2, instead of the bundled copy. Let's see if ​this PR is any good. I am now waiting for legacy build machines to test this.

@barracuda156 I removed your libxml2 patch for the second time. I think it is no longer relevant because we are now avoiding the down-level, bundled copy of libxml2.

[ryandesign (Ryan Carsten Schmidt)]

Replying to Dave-Allured:

Documentation of VTK build controls is sparse and inconsistent.

Now that I know what option you used, I searched for it and found this commit where FreeBSD also used it:

​https://lists.freebsd.org/archives/dev-commits-ports-all/2021-November/006873.html

And from there I found this documentation:

​https://gitlab.kitware.com/vtk/vtk/-/blob/master/Documentation/docs/build_instructions/build_settings.md

[Dave-Allured (Dave Allured)]

And from there I found this documentation:

​https://gitlab.kitware.com/vtk/vtk/-/blob/master/Documentation/docs/build_instructions/build_settings.md

Unfortunately there is a critical mistake in their listed setting for using external modules. I didn't figure it out until, like you, I web searched for someone else's working solution.

WRONG: VTK_MODULE_USE_EXTERNAL_<name>

CORRECT: VTK_MODULE_USE_EXTERNAL_VTK_<name>

I really should ask them about that some time.

[Dave-Allured (Dave Allured)]

In b2d8d6c187a6e91cf95110d20da583958cdc67d6/macports-ports (master):

vtk: use MacPorts libxml2 port

Closes: #71667