reserved identifiers in posix 2008 format ------ name, header, type, options identifier types ---------------- a any kind i filescope identifier d macro definition f function name x extern object name t typedef name s struct tag u union tag e enum tag m struct or union member c enum member (const) dc integer symbolic constant xd macro or extern object fd function and/or macro ti incomplete typedef type name si incomplete struct type tag ui incomplete union type tag macro parameters do not have namespace issues, jump labels and function or object identifiers with internal linkage (static) are covered by i and a types (the standard does not specify such identifiers), the i type includes t,s,u,e,m,c,ti,si,ui type identifiers as well f type identifiers can always have a macro implementation as well fd type identifiers are like f except they may be only implemented as a macro dc type identifiers are macros that may be defined as enum constants as well symbol types that may have external linkage: a,f,x,xd,fd symbol types that must have external linkage: f,x symbol types that may be macros: a,d,f,dc,xd,fd symbol types that must be macros: d,dc visibility constraints ---------------------- p defined identifier r reserved identifier or identifier pattern w weak identifier defined identifiers are made visible according to the identifier type when the header is included reserved identifiers may be provided by the implementation if the header is included weak identifiers are not defined in the header but they have special meaning (for d type it means the header behaviour is changed if it is defined before inclusion, for x type it means extern linkage symbol that the application can override) options ------- option names and option test macros in unistd.h: ADV _POSIX_ADVISORY_INFO CPT _POSIX_CPUTIME FSC _POSIX_FSYNC IP6 _POSIX_IPV6 MSG _POSIX_MESSAGE_PASSING MON _POSIX_MONOTONIC_CLOCK PIO _POSIX_PRIORITIZED_IO PS _POSIX_PRIORITY_SCHEDULING RS _POSIX_RAW_SOCKETS SHM _POSIX_SHARED_MEMORY_OBJECTS SPN _POSIX_SPAWN SS _POSIX_SPORADIC_SERVER SIO _POSIX_SYNCHRONIZED_IO TCT _POSIX_THREAD_CPUTIME TSA _POSIX_THREAD_ATTR_STACKADDR TSS _POSIX_THREAD_ATTR_STACKSIZE TPI _POSIX_THREAD_PRIO_INHERIT TPP _POSIX_THREAD_PRIO_PROTECT TPS _POSIX_THREAD_PRIORITY_SCHEDULING TSH _POSIX_THREAD_PROCESS_SHARED TSP _POSIX_THREAD_SPORADIC_SERVER RPI _POSIX_THREAD_ROBUST_PRIO_INHERIT RPP _POSIX_THREAD_ROBUST_PRIO_PROTECT TRC _POSIX_TRACE TEF _POSIX_TRACE_EVENT_FILTER TYM _POSIX_TYPED_MEMORY_OBJECTS XSR _XOPEN_STREAMS ML _POSIX_MEMLOCK MLR _POSIX_MEMLOCK_RANGE CD _POSIX2_C_DEV FD _POSIX2_FORT_DEV FR _POSIX2_FORT_RUN BE _POSIX2_PBS SD _POSIX2_SW_DEV UP _POSIX2_UPE UU _XOPEN_UUCP MX __STDC_IEC_559__ CX posix XSI _XOPEN_UNIX OB obsolete options that imply other options: XSR OB TEF OB TRC OB all but MX or OB CX feature test macros the application can define: _POSIX_C_SOURCE request everything except XSI and non-supported options _XOPEN_SOURCE request everything except non-supported options