When building SQLite 3.36.0 with SQLITE_OMIT_WAL and SQLITE_MAX_MMAP_SIZE=0 on OS X (and probably other unix systems) the build fails with:
Undefined symbols for architecture x86_64:
"_unixFcntlExternalReader", referenced from:
_unixFileControl in sqlite3-ede8e2.o
ld: symbol(s) not found for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)
make: *** [sqlite3] Error 1
The problem seems that unixFcntlExternalReader is omitted when SQLITE_OMIT_WAL. Though this method references to unixShmNode which is omitted with SQLITE_MAX_MMAP_SIZE=0.