c - Type definitions in POSIX/SUS headers -

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this question concerns various types need defined in required headers of posix/sus standard.

some types needs defined in many header files, , i'm wondering what's correct , compliant way of achieving this.

for instance, @ <time.h> header specification:

inclusion of header may make visible symbols <signal.h> header.

this straightforward, <signal.h> included <time.h>.

now this:

the clock_t, size_t, time_t, clockid_t, , timer_t types shall defined described in <sys/types.h>.

as understand it, means can't include <sys/types.h> <time.h>, expose more symbols required.

so can confirm this?
break standard compliance include <sys/types.h>?

if so, think best solution create specific header each type, particular type can made visible anywhere, without worrying other symbols.
is there other solution?

and last thing, types c standard?
lots of types in posix/sus specification integral types, , may need have fixed width.

so ok standard include <stdint.h> specific header, or break compliance?

you right exposing unwanted types , declarations additional headers non-conforming.

one trivial (but, in terms of time preprocessor spends opening files, expensive) solution have separate header each type, , whenever need, example, time_t, do:

#include <types/time_t.h>

of course types/time_t.h have appropriate multiple-inclusion guards.

there many other ways of achieving same. approach glibc , gcc use have special "needed" macros can define before including header asks nothing provide 1 or more types. solution expensive, moreso above, because breaks compilers' heuristics multiple-inclusion guards. compiler can't elide repeated inclusions; has parse file each time it's included.

the way in musl have single file, bits/alltypes.h, includes definitions of types needed multiple headers , macros control exposed. it's generated simple sed script hides macro logic:


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