psfex has two uninitialized global variables in the diagnostic.h header file. The Linux conda compilers are able to compile this because they set the -fcommon flag that treats all such variables as part of a global common block. The macOS conda compilers appear to have changed recently to use the standard default of -fno-common, which results in a duplicate symbol link error.

Please fix the code by making the global variable declarations extern and defining them in the diagnostic.c source file.