rejecting invalid values for n is fine even in the case where a new
sem will not be created, since the kernel does its range checks on n
even in this case as well.
by default, the kernel will bound the limit well below USHRT_MAX
anyway, but it's presumably possible that an administrator could
override this limit and break things.
this type is not really intended to be used; it's just there to allow
implementations to choose the type for the shm_nattch member of
struct shmid_sh, presumably since historical implementations disagreed
on the type. in any case, it needs to be there, so now it is.
the pathnames prefixed with /dev/null/ are guaranteed never to be
valid. the previous use of /dev/null alone was mildly dangerous in
that bad software might attempt to unlink the name when it found a
non-regular file there and create a new file.
despite declaring functions that take arguments of type va_list, these
headers are not permitted by the c standard to expose the definition
of va_list, so an alias for the type must be used. the name
__isoc_va_list was chosen to convey that the purpose of this alternate
name is for iso c conformance, and to avoid the multitude of names
which gcc mangles with its hideous "fixincludes" monstrosity, leading
to serious header breakage if these "fixes" are run.
also move all legacy inet_* functions into a single file to avoid
wasting object file and compile time overhead on them.
the added functions are legacy interfaces for working with classful
ipv4 network addresses. they have no modern usefulness whatsoever, but
some programs unconditionally use them anyway, and they're tiny.
based on patch by Strake with minor stylistic changes, and combined
into a single file. this patch remained open for a long time due to
some question as to whether ether_aton would be better implemented in
terms of sscanf, and it's time something was committed, so here it is.
arguably CLOCK_MONOTONIC should be redirected to CLOCK_BOOTTIME with a
fallback for old kernels that don't support it, since Linux's
CLOCK_BOOTTIME semantics seem to match the spirit of the POSIX
requirements for CLOCK_MONOTONIC better than Linux's version of
CLOCK_MONOTONIC does. however, this is a change that would require
further discussion and research, so for now, I'm simply making them
all available.
originally it was right on 32-bit archs and wrong on 64-bit, but after
recent changes it was wrong everywhere. with this commit, it's now
right everywhere.
there was some question as to how many decimal places to use, since
one decimal place is always sufficient to identify the smallest
denormal uniquely. for now, I'm following the example in the C
standard which is consistent with the other min/max macros we already
had in place.
somehow I missed this when removing the corresponding
__STDC_LIMIT_MACROS and __STDC_CONSTANT_MACROS nonsense from stdint.h.
these were all attempts by the C committee to guess what the C++
committee would want, and the guesses turned out to be wrong.
__FLOAT_BITS and __DOUBLE_BITS macros used union compound literals,
now they are changed into static inline functions. A good C compiler
generates the same code for both and the later is C++ conformant.
C++11, the first C++ with stdint.h, requires the previously protected
macros to be exposed unconditionally by stdint.h. apparently these
checks were an early attempt by the C committee to guess what the C++
committee would want, and they guessed wrong.
the getifaddrs interface seems to have been invented by glibc, and
they expose socket.h, so for us not to do so is just gratuitous
incompatibility with the interface we're mimicing.
this is a bit ugly, and the motivation for supporting it is
questionable. however the main factors were:
1. it will be useful to have this for certain internal purposes
anyway -- things like syslog.
2. applications can just save argv[0] in main, but it's hard to fix
non-portable library code that's depending on being able to get the
invocation name without the main application's help.
supports ipv4 and ipv6, but not the "extended" usage where
usage statistics and other info are assigned to ifa_data members
of duplicate entries with AF_PACKET family.
the preprocessor can reliably determine the signedness of wchar_t.
L'\0' is used for 0 in the expressions so that, if the underlying type
of wchar_t is long rather than int, the promoted type of the
expression will match the type of wchar_t.
since shadow does not yet support enumeration (getspent), the
corresponding FILE-based get and put versions are also subbed out for
now. this is partly out of laziness and partly because it's not clear
how they should work in the presence of TCB shadow files. the stubs
should make it possible to compile some software that expects them to
exist, but such software still may not work properly.
this type was removed back in 5243e5f160 ,
because it was removed from the XSI specs.
however some apps use it.
since it's in the POSIX reserved namespace, we can expose it
unconditionally.
this fix is far from ideal and breaks the rule of not using
arch-specific #ifdefs, but for now we just need a solution to the
existing breakage.
the underlying problem is that the kernel folks made a very stupid
decision to make misalignment of this struct part of the kernel
API/ABI for x86_64, in order to avoid writing a few extra lines of
code to handle both 32- and 64-bit userspace on 64-bit kernels. I had
just added the packed attribute unconditionally thinking it was
harmless on 32-bit archs, but non-x86 32-bit archs have 8-byte
alignment on 64-bit types.
based on patch contributed by Anthony G. Basile (blueness)
some issues remain with the filename generation algorithm and other
small bugs, but this patch has been sitting around long enough that I
feel it's best to get it committed and then work out any remaining
issues.
based on patch by Isaac Dunham, moved to its own file to avoid
increasing bss on static linked programs not using this nonstandard
function but using the standard getgrent function, and vice versa.
the main goal of these changes is to address the case where an
application provides a stack of size N, but TLS has size M that's a
significant portion of the size N (or even larger than N), thus giving
the application less stack space than it expected or no stack at all!
the new strategy pthread_create now uses is to only put TLS on the
application-provided stack if TLS is smaller than 1/8 of the stack
size or 2k, whichever is smaller. this ensures that the application
always has "close enough" to what it requested, and the threshold is
chosen heuristically to make sure "sane" amounts of TLS still end up
in the application-provided stack.
if TLS does not fit the above criteria, pthread_create uses mmap to
obtain space for TLS, but still uses the application-provided stack
for actual call frame stack. this is to avoid wasting memory, and for
the sake of supporting ugly hacks like garbage collection based on
assumptions that the implementation will use the provided stack range.
in order for the above heuristics to ever succeed, the amount of TLS
space wasted on POSIX TSD (pthread_key_create based) needed to be
reduced. otherwise, these changes would preclude any use of
pthread_create without mmap, which would have serious memory usage and
performance costs for applications trying to create huge numbers of
threads using pre-allocated stack space. the new value of
PTHREAD_KEYS_MAX is the minimum allowed by POSIX, 128. this should
still be plenty more than real-world applications need, especially now
that C11/gcc-style TLS is now supported in musl, and most apps and
libraries choose to use that instead of POSIX TSD when available.
at the same time, PTHREAD_STACK_MIN has been decreased. it was
originally set to PAGE_SIZE back when there was no support for TLS or
application-provided stacks, and requests smaller than a whole page
did not make sense. now, there are two good reasons to support
requests smaller than a page: (1) applications could provide
pre-allocated stacks smaller than a page, and (2) with smaller stack
sizes, stack+TLS+TSD can all fit in one page, making it possible for
applications which need huge numbers of threads with minimal stack
needs to allocate exactly one page per thread. the new value of
PTHREAD_STACK_MIN, 2k, is aligned with the minimum size for
sigaltstack.
alternatively, we could define it in sys/socket.h since SO* is
reserved there, and tcp.h includes sys/socket.h in extensions mode.
note that SOL_TCP is simply wrong and it's only here for compatibility
with broken applications. the correct argument to pass for setting TCP
socket options is IPPROTO_TCP, which of course has the same value as
SOL_TCP but works everywhere.
this is a trivial no-op, because dlclose never deletes libraries. thus
we might as well have it in the header in case some application wants
it, since we're already providing it anyway.
based on patch by Pierre Carrier <pierre@gcarrier.fr> that just added
the flag constant, but with minimal additional code so that it
actually works as documented. this is a nonstandard option but some
major software (reportedly, Firefox) uses it and it was easy to add
anyway.
the historical mess of having different definitions for C and C++
comes from the historical C definition as (void *)0 and the fact that
(void *)0 can't be used in C++ because it does not convert to other
pointer types implicitly. however, using plain 0 in C++ exposed bugs
in C++ programs that call variadic functions with NULL as an argument
and (wrongly; this is UB) expect it to arrive as a null pointer. on
64-bit machines, the high bits end up containing junk. glibc dodges
the issue by using a GCC extension __null to define NULL; this is
observably non-conforming because a conforming application could
observe the definition of NULL via stringizing and see that it is
neither an integer constant expression with value zero nor such an
expression cast to void.
switching to 0L eliminates the issue and provides compatibility with
broken applications, since on all musl targets, long and pointers have
the same size, representation, and argument-passing convention. we
could maintain separate C and C++ definitions of NULL (i.e. just use
0L on C++ and use (void *)0 on C) but after careful analysis, it seems
extremely difficult for a C program to even determine whether NULL has
integer or pointer type, much less depend in subtle, unintentional
ways, on whether it does. C89 seems to have no way to make the
distinction. on C99, the fact that (int)(void *)0 is not an integer
constant expression, along with subtle VLA/sizeof semantics, can be
used to make the distinction, but many compilers are non-conforming
and give the wrong result to this test anyway. on C11, _Generic can
trivially make the distinction, but it seems unlikely that code
targetting C11 would be so backwards in caring which definition of
NULL an implementation uses.
as such, the simplest path of using the same definition for NULL in
both C and C++ was chosen. the #undef directive was also removed so
that the compiler can catch and give a warning or error on
redefinition if buggy programs have defined their own versions of
NULL prior to inclusion of standard headers.
Rich Felker
Szabolcs Nagy
rofl0r