http://clang.llvm.org/docs/AttributeReference.html#nonnull
_Nonnull is similar to the nonnull attribute in that it will instruct
compilers to warn the user if it can prove that a null argument is
being passed. Unlike the nonnull attribute, this annotation indicated
that a value *should not* be null, not that it *cannot* be null, or
even that the behavior is undefined. The important distinction is that
the optimizer will perform surprising optimizations like the
following:
void foo(void*) __attribute__(nonnull, 1);
int bar(int* p) {
foo(p);
// The following null check will be elided because nonnull
// attribute means that, since we call foo with p, p can be
// assumed to not be null. Thus this will crash if we are called
// with a null pointer.
if (src != NULL) {
return *p;
}
return 0;
}
int main() {
return bar(NULL);
}
Note that by doing this we are no longer attaching any sort of
attribute for GCC (GCC doesn't support attaching nonnull directly to a
parameter, only to the function and naming the arguments
positionally). This means we won't be getting a warning for this case
from GCC any more. People that listen to warnings tend to use clang
anyway, and we're quickly moving toward that as the default, so this
seems to be an acceptable tradeoff.
Change-Id: Ie05fe7cec2f19a082c1defb303f82bcf9241b88d
Add signalfd() call to bionic.
Adding the signalfd call was done in 3 steps:
- add signalfd4 system call (function name and syscall
number) to libc/SYSCALLS.TXT
- generate all necessary headers by calling
libc/tools/gensyscalls.py. This patch is adding
the generated files since the build system
does not call gensyscalls.py.
- create the signalfd wrapper in signalfd.cpp and add
the function prototype to sys/signalfd.h
(cherry-pick of 0c11611c11, modified to
work with older versions of GCC still in use on some branches.)
Change-Id: I4c6c3f12199559af8be63f93a5336851b7e63355
Elliott Hughes
Josh Gao
Dan Albert
Rom Lemarchand