On Mon, Jul 01, 2013 at 10:54:56AM +0100, Peter Maydell wrote:
> On 1 July 2013 10:35, Stefan Hajnoczi <stefa...@redhat.com> wrote:
> > From: Paolo Bonzini <pbonz...@redhat.com>
> >
> > Fast TLS is not available on some platforms, but it is always nice to
> > use it. This wrapper implementation falls back to pthread_get/setspecific
> > on POSIX systems that lack __thread, but uses the dynamic linker's TLS
> > support on Linux and Windows.
> >
> > The user shall call tls_alloc_foo() in every thread that needs to access
> > the variable---exactly once and before any access. foo is the name of
> > the variable as passed to DECLARE_TLS and DEFINE_TLS. Then,
> > tls_get_foo() will return the address of the variable. It is guaranteed
> > to remain the same across the lifetime of a thread, so you can cache it.
>
> > ##########################################
> > +# check for TLS runtime
> > +
> > +# Some versions of mingw include the "magic" definitions that make
> > +# TLS work, some don't. Check for it.
> > +
> > +if test "$mingw32" = yes; then
> > + cat > $TMPC << EOF
> > +int main(void) {}
>
> Execution falls off the end of function without returning a value
> (I would expect the compiler to issue a warning about this.)
You are right, gcc emits a warning.
> > +#ifndef QEMU_TLS_H
> > +#define QEMU_TLS_H
> > +
> > +#if defined __linux__
> > +#define DECLARE_TLS(type, x) \
> > +extern __thread typeof(type) x; \
> > + \
> > +static inline typeof(type) *tls_get_##x(void) \
> > +{ \
> > + return &x; \
> > +} \
> > + \
> > +static inline typeof(type) *tls_alloc_##x(void) \
> > +{ \
> > + return &x; \
> > +} \
> > + \
> > +extern int dummy_##__LINE__
>
> What's this for?
It makes the DECLARE_TLS() macro use a semicolon.
