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2015-03-03make all objects used with atomic operations volatileRich Felker1-1/+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.
2014-09-05add missing legacy LFS *64 symbol aliasesSzabolcs Nagy1-0/+4
versionsort64, aio*64 and lio*64 symbols were missing, they are only needed for glibc ABI compatibility, on the source level dirent.h and aio.h already redirect them.
2014-02-25fix readdir not to set ENOENT when directory is removed while readingRich Felker1-2/+7
per POSIX, ENOENT is reserved for invalid stream position; it is an optional error and would only happen if the application performs invalid seeks on the underlying file descriptor. however, linux's getdents syscall also returns ENOENT if the directory was removed between the time it was opened and the time of the read. we need to catch this case and remap it to simple end-of-file condition (null pointer return value like an error, but no change to errno). this issue reportedly affects GNU make in certain corner cases. rather than backing up and restoring errno, I've just changed the syscall to be made in a way that doesn't affect errno (via an inline syscall rather than a call to the __getdents function). the latter still exists for the purpose of providing the public getdents alias which sets errno.
2013-12-12include cleanups: remove unused headers and add feature test macrosSzabolcs Nagy5-15/+2
2013-07-22refactor headers, especially alltypes.h, and improve C++ ABI compatRich Felker1-1/+1
the arch-specific bits/alltypes.h.sh has been replaced with a generic alltypes.h.in and minimal arch-specific bits/alltypes.h.in. this commit is intended to have no functional changes except: - exposing additional symbols that POSIX allows but does not require - changing the C++ name mangling for some types - fixing the signedness of blksize_t on powerpc (POSIX requires signed) - fixing the limit macros for sig_atomic_t on x86_64 - making dev_t an unsigned type (ABI matching goal, and more logical) in addition, some types that were wrongly defined with long on 32-bit archs were changed to int, and vice versa; this change is non-functional except for the possibility of making pointer types mismatch, and only affects programs that were using them incorrectly, and only at build-time, not runtime. the following changes were made in the interest of moving non-arch-specific types out of the alltypes system and into the headers they're associated with, and also will tend to improve application compatibility: - netdb.h now includes netinet/in.h (for socklen_t and uint32_t) - netinet/in.h now includes sys/socket.h and inttypes.h - sys/resource.h now includes sys/time.h (for struct timeval) - sys/wait.h now includes signal.h (for siginfo_t) - langinfo.h now includes nl_types.h (for nl_item) for the types in stdint.h: - types which are of no interest to other headers were moved out of the alltypes system. - fast types for 8- and 64-bit are hard-coded (at least for now); only the 16- and 32-bit ones have reason to vary by arch. and the following types have been changed for C++ ABI purposes; - mbstate_t now has a struct tag, __mbstate_t - FILE's struct tag has been changed to _IO_FILE - DIR's struct tag has been changed to __dirstream - locale_t's struct tag has been changed to __locale_struct - pthread_t is defined as unsigned long in C++ mode only - fpos_t now has a struct tag, _G_fpos64_t - fsid_t's struct tag has been changed to __fsid_t - idtype_t has been made an enum type (also required by POSIX) - nl_catd has been changed from long to void * - siginfo_t's struct tag has been removed - sigset_t's has been given a struct tag, __sigset_t - stack_t has been given a struct tag, sigaltstack - suseconds_t has been changed to long on 32-bit archs - [u]intptr_t have been changed from long to int rank on 32-bit archs - dev_t has been made unsigned summary of tests that have been performed against these changes: - nsz's libc-test (diff -u before and after) - C++ ABI check symbol dump (diff -u before, after, glibc) - grepped for __NEED, made sure types needed are still in alltypes - built gcc 3.4.6
2012-09-06use restrict everywhere it's required by c99 and/or posix 2008Rich Felker1-1/+1
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.
2012-06-13add (currently stubbed due to stubbed strverscmp) versionsort functionRich Felker1-0/+8
based on patch by Emil Renner Berthing, with minor changes to dirent.h for LFS64 and organization of declarations this code should work unmodified once a real strverscmp is added, but I've been hesitant to add it because the GNU strverscmp behavior is harmful in a lot of cases (for instance if you have numeric filenames in hex). at some point I plan on trying to design a variant of the algorithm that behaves better on a mix of filename styles.
2012-04-24ditch the priority inheritance locks; use malloc's version of lockRich Felker5-12/+9
i did some testing trying to switch malloc to use the new internal lock with priority inheritance, and my malloc contention test got 20-100 times slower. if priority inheritance futexes are this slow, it's simply too high a price to pay for avoiding priority inversion. maybe we can consider them somewhere down the road once the kernel folks get their act together on this (and perferably don't link it to glibc's inefficient lock API)... as such, i've switch __lock to use malloc's implementation of lightweight locks, and updated all the users of the code to use an array with a waiter count for their locks. this should give optimal performance in the vast majority of cases, and it's simple. malloc is still using its own internal copy of the lock code because it seems to yield measurably better performance with -O3 when it's inlined (20% or more difference in the contention stress test).
2011-07-21fix errno value when fdopendir is given an invalid file descriptorRich Felker1-1/+4
this resolves an issue reported by Vasiliy Kulikov
2011-06-25optimize opendir using O_CLOEXECRich Felker1-2/+1
2011-06-06fix handling of d_name in struct direntRich Felker1-4/+3
basically there are 3 choices for how to implement this variable-size string member: 1. C99 flexible array member: breaks using dirent.h with pre-C99 compiler. 2. old way: length-1 string: generates array bounds warnings in caller. 3. new way: length-NAME_MAX string. no problems, simplifies all code. of course the usable part in the pointer returned by readdir might be shorter than NAME_MAX+1 bytes, but that is allowed by the standard and doesn't hurt anything.
2011-04-18avoid fd leak if opendir is cancelled when calloc has failedRich Felker1-1/+2
2011-04-11fix errno handling in scandir:Rich Felker1-2/+1
1. saved errno was not being restored, illegally clearing errno to 0. 2. no need to backup and save errno around free; it will not touch except perhaps when the program has already invoked UB...
2011-03-20global cleanup to use the new syscall interfaceRich Felker1-1/+1
2011-02-15finish moving 32-bit-specific junk out of source files.Rich Felker1-1/+1
2011-02-12initial check-in, version 0.5.0v0.5.0Rich Felker13-0/+244