Portable Object Compiler 3.3.42 seems to compile fine using the latest byacc - 2.0 20240109
Any version of byacc should work, for convenience I have byacc 1.9.1 on the byacc files folder on this site but if the operating system (such as OpenBSD) has a native Berkeley yacc package (which is called yacc and not byacc there) that version of yacc can be used of course.
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Portable Object Compiler 3.3.42 seems to compile fine using the latest byacc - 2.0 20240109
Any version of byacc should work, for convenience I have byacc 1.9.1 on the byacc files folder on this site but if the operating system (such as OpenBSD) has a native Berkeley yacc package (which is called yacc and not byacc there) that version of yacc can be used of course.