flex: Missing -Wl,-undefined -Wl,dynamic_lookup) in libtool.m4

[vdoublie]

Many ports fail to build under Xcode 12.0 and macOS11.0 due to failure to include required .h files.

Typical error are (like the one taken from port flex):

:info:build Undefined symbols for architecture x86_64:
:info:build   "_yylex", referenced from:
:info:build       _main in libmain.o

this was a warning with previous macOS version and Xcode, it is now an error.

[ryandesign (Ryan Carsten Schmidt)]

Each port will need an individual fix. Let's make this ticket about flex. Do you know which header needs to be included in which file to fix this?

[vdoublie]

Actually it turns out that flex is not missing a simple include, but rather missing linker options (-Wl,-undefined -Wl,dynamic_lookup) which are not configured because configure script has (of course) not been updated to handle macOS 11.

I have attached a patch file that will fix this issue for flex (essentially the same fix as required for gcc10).

The following should be added to the Portfile in order to make use of it:

patchfiles          libtool.m4.diff

post-patch {
    system "cd ${worksrcpath} && autoreconf"
}

Unless of course the patch can be applied upstream.

Many thanks in advance.

Best regards, Vanessa

[ryandesign (Ryan Carsten Schmidt)]

Thanks. We're still learning what the various problems on macOS 11 look like. I'll instead use the libtool.m4 patch that Jeremy committed to the libtool port in June.

[ryandesign (Ryan Carsten Schmidt)]

In f6fc0fec20aedb9809648326454678e97243eaa6/macports-ports (master):

flex: Patch libtool.m4 to recognize macOS 11+

Closes: #60937