| Message ID | 20201203191409.3906D203C3@pchp3.se.axis.com |
|---|---|
| State | New |
| Headers | show |
| Series | v2: doc/implement-c.texi: About same-as-scalar-type volatile aggregate accesses, PR94600 | expand |
On 12/3/20 12:14 PM, Hans-Peter Nilsson via Gcc-patches wrote: > Belatedly, here's an updated version, using Martin Sebor's > suggested wording from > "https://gcc.gnu.org/pipermail/gcc-patches/2020-July/549580.html". > I added two commas, hopefully helpfully. Albeit ok'd by Richard > Biener in > "https://gcc.gnu.org/pipermail/gcc-patches/2020-July/549922.html", > better have this reviewed properly, including markup (none added). > > Ok for trunk (gcc-11) and gcc-10? Thanks for taking my suggestion! These are just formatting nits but I would only further suggest to enclose the name S (since it names a type) and the second volatile in an @code{} directive (since it's a keyword). (The volatile in volatile access is not one so it shouldn't be formatted that way.) Martin > > > --- > We say very little about reads and writes to aggregate / > compound objects, just scalar objects (i.e. assignments don't > cause reads). Let's lets say something safe about aggregate > objects, but only for those that are the same size as a scalar > type. > > There's an equal-sounding section (Volatiles) in extend.texi, > but this seems a more appropriate place, as specifying the > behavior of a standard qualifier. > > gcc: > > 2020-12-02 Hans-Peter Nilsson <hp@axis.com> > Martin Sebor <msebor@redhat.com> > > PR middle-end/94600 > * doc/implement-c.texi (Qualifiers implementation): Add blurb > about access to the whole of a volatile aggregate object, only for > same-size as a scalar object. > --- > gcc/doc/implement-c.texi | 5 +++++ > 1 file changed, 5 insertions(+) > > diff --git a/gcc/doc/implement-c.texi b/gcc/doc/implement-c.texi > index 692297b69c4..2e9158a2a45 100644 > --- a/gcc/doc/implement-c.texi > +++ b/gcc/doc/implement-c.texi > @@ -576,6 +576,11 @@ are of scalar types, the expression is interpreted by GCC as a read of > the volatile object; in the other cases, the expression is only evaluated > for its side effects. > > +When an object of an aggregate type, with the same size and alignment as a > +scalar type S, is the subject of a volatile access by an assignment > +expression or an atomic function, the access to it is performed as if the > +object's declared type were volatile S. > + > @end itemize > > @node Declarators implementation >
diff --git a/gcc/doc/implement-c.texi b/gcc/doc/implement-c.texi index 692297b69c4..2e9158a2a45 100644 --- a/gcc/doc/implement-c.texi +++ b/gcc/doc/implement-c.texi @@ -576,6 +576,11 @@ are of scalar types, the expression is interpreted by GCC as a read of the volatile object; in the other cases, the expression is only evaluated for its side effects. +When an object of an aggregate type, with the same size and alignment as a +scalar type S, is the subject of a volatile access by an assignment +expression or an atomic function, the access to it is performed as if the +object's declared type were volatile S. + @end itemize @node Declarators implementation