path: root/include/aio.h
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2019-10-28add time64 symbol name redirects to public headers, under arch controlRich Felker-0/+4
a _REDIR_TIME64 macro is introduced, which the arch's alltypes.h is expected to define, to control redirection of symbol names for interfaces that involve time_t and derived types. this ensures that object files will only be linked to libc interfaces matching the ABI whose headers they were compiled against. along with time32 compat shims, which will be introduced separately, the redirection also makes it possible for a single libc (static or shared) to be used with object files produced with either the old (32-bit time_t) headers or the new ones after 64-bit time_t switchover takes place. mixing of such object files (or shared libraries) in the same program will also be possible, but must be done with care; ABI between libc and a consumer of the libc interfaces is guaranteed to match by the the symbol name redirection, but pairwise ABI between consumers of libc that define interfaces between each other in terms of time_t is not guaranteed to match. this change adds a dependency on an additional "GNU C" feature to the public headers for existing 32-bit archs, which is generally undesirable; however, the feature is one which glibc has depended on for a long time, and thus which any viable alternative compiler is going to need to provide. 64-bit archs are not affected, nor will future 32-bit archs be, regardless of whether they are "new" on the kernel side (e.g. riscv32) or just newly-added (e.g. a new sparc or xtensa port). the same applies to newly-added ABIs for existing machine-level archs.
2015-03-03make all objects used with atomic operations volatileRich Felker-1/+1
the memory model we use internally for atomics permits plain loads of values which may be subject to concurrent modification without requiring that a special load function be used. since a compiler is free to make transformations that alter the number of loads or the way in which loads are performed, the compiler is theoretically free to break this usage. the most obvious concern is with atomic cas constructs: something of the form tmp=*p;a_cas(p,tmp,f(tmp)); could be transformed to a_cas(p,*p,f(*p)); where the latter is intended to show multiple loads of *p whose resulting values might fail to be equal; this would break the atomicity of the whole operation. but even more fundamental breakage is possible. with the changes being made now, objects that may be modified by atomics are modeled as volatile, and the atomic operations performed on them by other threads are modeled as asynchronous stores by hardware which happens to be acting on the request of another thread. such modeling of course does not itself address memory synchronization between cores/cpus, but that aspect was already handled. this all seems less than ideal, but it's the best we can do without mandating a C11 compiler and using the C11 model for atomics. in the case of pthread_once_t, the ABI type of the underlying object is not volatile-qualified. so we are assuming that accessing the object through a volatile-qualified lvalue via casts yields volatile access semantics. the language of the C standard is somewhat unclear on this matter, but this is an assumption the linux kernel also makes, and seems to be the correct interpretation of the standard.
2012-09-07default features: make musl usable without feature test macrosRich Felker-6/+1
the old behavior of exposing nothing except plain ISO C can be obtained by defining __STRICT_ANSI__ or using a compiler option (such as -std=c99) that predefines it. the new default featureset is POSIX with XSI plus _BSD_SOURCE. any explicit feature test macros will inhibit the default. installation docs have also been updated to reflect this change.
2012-09-06use restrict everywhere it's required by c99 and/or posix 2008Rich Felker-1/+7
to deal with the fact that the public headers may be used with pre-c99 compilers, __restrict is used in place of restrict, and defined appropriately for any supported compiler. we also avoid the form [restrict] since older versions of gcc rejected it due to a bug in the original c99 standard, and instead use the form *restrict.
2012-07-19fix typo in aio.hRich Felker-1/+1
2012-06-04_GNU_SOURCE is supposed to imply _LARGEFILE64_SOURCERich Felker-1/+1
this is ugly and stupid, but now that the *64 symbol names exist, a lot of broken GNU software detects them in configure, then either breaks during build due to missing off64_t definition, or attempts to compile without function declarations/prototypes. "fixing" it here is easier than telling everyone to add yet another feature test macro to their builds.
2012-05-04add support for ugly *64 functions with _LARGEFILE64_SOURCERich Felker-0/+13
musl does not support legacy 32-bit-off_t whatsoever. off_t is always 64 bit, and correct programs that use off_t and the standard functions will just work out of the box. (on glibc, they would require -D_FILE_OFFSET_BITS=64 to work.) however, some programs instead define _LARGEFILE64_SOURCE and use alternate versions of all the standard types and functions with "64" appended to their names. we do not want code to actually get linked against these functions (it's ugly and inconsistent), so macros are used instead of prototypes with weak aliases in the library itself. eventually the weak aliases may be added at the library level for the sake of using code that was originally built against glibc, but the macros will still be the desired solution in the headers.
2012-04-03remove useless (at best, harmful) feature test checks in aio.hRich Felker-5/+0
2011-09-28stupid typo (caused by rather ugly spelling in POSIX..) in aioRich Felker-1/+1
2011-09-13fix return types for aio_read and aio_write againRich Felker-2/+2
previous fix was backwards and propagated the wrong type rather than the right one...
2011-09-13fix various errors in function signatures/prototypes found by nszRich Felker-2/+2
2011-09-13fix prototypes for aio_read and aio_writeRich Felker-2/+2
2011-09-09implement POSIX asynchronous ioRich Felker-0/+60
some features are not yet supported, and only minimal testing has been performed. should be considered experimental at this point.