gcc9 @9.3.0_4 gfortran fails with "ld: library not found for -lSystem" in Big Sur

[cquike]

In a fresh installed Big Sur machine with a fresh installed macports the gfortran command fails to compile (link) a hello world Fortran program:

$ gfortran-mp-9 -o hello hello.f 

ld: library not found for -lSystem
collect2: error: ld returned 1 exit status

I have also tried with gfortran-mp-8 with the same results. The same command in a macOS 10.15 machine doesn't give any error.

The versions installed are:

# port installed | grep gcc
  gcc8 @8.4.0_2 (active)
  gcc9 @9.3.0_4 (active)
  gcc_select @0.1_9 (active)
  libgcc @3.0_0 (active)
  libgcc8 @8.4.0_1 (active)
  libgcc9 @9.3.0_3 (active)
  libgcc10 @10.2.0_3 (active)

# sw_vers
ProductName:	macOS
ProductVersion:	11.1
BuildVersion:	20C69

#/usr/bin/xcodebuild -version
Xcode 12.3
Build version 12C33

The hello.f example is the simplest Fortran program:

      PROGRAM HELLO
*     The PRINT statement is like WRITE,
*     but prints to the standard output unit
        PRINT '(A)', 'Hello, world'
        STOP
      END

[kencu (Ken)]

please do this:

gfortran-mp-9 -v -o hello hello.f 

and perhaps also:

gfortran-mp-9 -v -Wl,-v -Wa,-v -o hello hello.f 

[kencu (Ken)]

99.999% chance it is the same problem we have with all the gccs -- the SDK moved by a decimal point, and so gcc is broken.

see this thread <​https://lists.macports.org/pipermail/macports-dev/2021-January/042775.html>

We cannot as yet get agreement to build gcc against "MacOSX.sdk" on new systems, but -- we will.

[mascguy (Christopher Nielsen)]

While not quite the same symptoms, could be a similar situation to issue:62070.

[jmroot (Joshua Root)]

Replying to kencu:

We cannot as yet get agreement to build gcc against "MacOSX.sdk" on new systems, but -- we will.

The real bug there is of course that gcc insists on using the same SDK it was built against at runtime.

[kencu (Ken)]

Iain and Jeremy had a different idea of what that option was supposed to mean. I don't believe Iain feels there is any bug there to be fixed.

[cquike]

Output of "gfortran-mp-9 -v -Wl,-v -Wa,-v -o hello hello.f "

[cquike]

I have attached the output of "gfortran-mp-9 -v -Wl,-v -Wa,-v -o hello hello.f". It indeed mentions /Library/Developer/CommandLineTools/SDKs/MacOSX11.0.sdk which is not present in my system:

# ls -l /Library/Developer/CommandLineTools/SDKs/
total 0
lrwxr-xr-x  1 root  wheel   14 Jan 21 12:29 MacOSX.sdk -> MacOSX11.1.sdk
drwxr-xr-x  8 root  wheel  256 Jul  9  2020 MacOSX10.15.sdk
drwxr-xr-x  7 root  wheel  224 Nov 30 13:33 MacOSX11.1.sdk

[kencu (Ken)]

so the simplest thing to do is make a symlink from MacOSX11.0.sdk to MacOSX11.1.sdk and that gets you fixed for right now.

To fix this correctly, remove that symlink if you make it, and rebuild gcc from source on your local machine, like this:

sudo port -v -s install gcc9

and btw, gcc10 is available if that might be better. It probably also needs an SDK rebuild, sorry.

we are trying to get to a compromise on how we'll fix this properly, hopefully without too much more time going by.

[cquike]

The symlink workaround is working.

Looking forward for proper fix.

Thanks you for the help!