this is a popular extension some programs depend on, and by using a
temporary buffer and strdup rather than malloc prior to the syscall,
i've avoided the dependency on free and thus minimized the bloat cost
of supporting this feature.

this is necessitated by the ugly <syscall.h> just added

these will also avoid obnoxious warnings with gcc -Wbraces.

apparently some broken stuff (libstdc++) needs this.

this was discussed on the mailing list and no consensus on the
preferred solution was reached, so in anticipation of a release, i'm
just committing a minimally-invasive solution that avoids the problem
by ensuring that multi-threaded-capable programs will always have
initialized the thread pointer before any signal handler can run.

in the long term we may switch to initializing the thread pointer at
program start time whenever the program has the potential to access
any per-thread data.

GNU programs may expect the GNU version of basename, which has a
different prototype (argument is const-qualified) and prototype it
themselves too. of course if they're expecting the GNU behavior for
the function, they'll still run into problems, but at least this
eliminates some compile-time failures.

since gcc is failing to generate the necessary ".hidden" directive in
the output asm, generate it explicitly with an __asm__ statement...

this was a failed attempt at working around the gcc 3 visibility bug
affecting x86_64. subsequent patch will address it with an ugly but
working hack.

in gcc 3, the visibility attribute must be placed on both the
declaration and on the definition. if it's omitted from the
definition, the compiler fails to emit the ".hidden" directive in the
assembly, and the linker will either generate textrels (if supported,
such as on i386) or refuse to link (on targets where certain types of
textrels are forbidden or impossible without further assumptions about
memory layout, such as on x86_64).

this patch also unifies the decision about when to use visibility into
libc.h and makes the visibility in the utf-8 state machine tables
based on libc.h rather than a duplicate test.

uninitialized file descriptor was being closed on return, causing
stdin to be closed in many cases.

while probably desirable, changing the default language variant is
outside the scope of the wrapper's responsibility.

1. don't try to install (and thus build) shared libs when they were
disabled in config.mak

2. ensure that the path for the dynamic linker exists before
attempting to install it.

even if pthread_create/exit code is not linked, run flag needs to be
checked and cleanup function potentially run on pop. thus, move the
code to the module that's always linked when pthread_cleanup_push/pop
is used.

the old abi was intended to duplicate glibc's abi at the expense of
being ugly and slow, but it turns out glib was not even using that abi
except on non-gcc-compatible compilers (which it doesn't even support)
and was instead using an exceptions-in-c/unwind-based approach whose
abi we could not duplicate anyway without nasty dwarf2/unwind
integration.

the new abi is copied from a very old glibc abi, which seems to still
be supported/present in current glibc. it avoids all unwinding,
whether by sjlj or exceptions, and merely maintains a linked list of
cleanup functions to be called from the context of pthread_exit. i've
made some care to ensure that longjmp out of a cleanup function should
work, even though it is not required to.

this change breaks abi compatibility with programs which were using
pthread cancellation, which is unfortunate, but that's why i'm making
the change now rather than later. considering that most pthread
features have not been usable until recently anyway, i don't see it as
a major issue at this point.

i'm not sure that it's "correct" for dlopen to block cancellation
when calling constructors for libraries it loads, but it sure seems
like the right thing. in any case, dlopen itself needs cancellation
blocked.

note that it still will have the standards-conformant behavior, not
the GNU behavior. but at least this prevents broken code from ending
up with truncated pointers due to implicit declarations...

per 7.18.4: Each invocation of one of these macros shall expand to an
integer constant expression suitable for use in #if preprocessing
directives. The type of the expression shall have the same type as
would an expression of the corresponding type converted according to
the integer promotions. The value of the expression shall be that of
the argument.

the key phrase is "converted according to the integer promotions".
thus there is no intent or allowance that the expression have
smaller-than-int types.

this should be everything except for some functions where the non-_l
version isn't even implemented yet (mainly some non-ISO-C wcs*
functions).

untested; should work.

this is mainly in hopes of supporting c++ (not yet possible for other
reasons) but will also help applications/libraries which use (and more
often, abuse) the gcc __attribute__((__constructor__)) feature in "C"
code.

x86_64 and arm versions of the new startup asm are untested and may
have minor problems.

these have not been heavily tested, but they should work as described
in the old standards. probably broken for non-finite values...