This macro checks to see if sys/sem.h defines struct semun. Some systems do, some systems don’t. Your code must be able to deal with this possibility; if HAVE_STRUCT_SEMUM isn’t defined for a given system, you have to define this structure before you can call functions like semctl().
You should call AX_SYSV_IPC before this macro, to separate the check for System V IPC headers from the check for struct semun.
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Copyright © 2008 Warren Young email@example.com
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