On Mon, Oct 12, 2015 at 04:07:48PM -0700, David Wohlferd wrote: > Index: extend.texi > =================================================================== > --- extend.texi (revision 228690) > +++ extend.texi (working copy) > @@ -8506,7 +8506,8 @@ > @cindex global register variables > @cindex registers, global variables in > > -You can define a global register variable in GNU C like this: > +You can define a global register variable and associate it with a specified > register
Line too long. I know quite a bit of doc does that, but that's no excuse :-) > +Registers can be a limited resource on some systems and allowing the They are a limited resource on almost all systems. "Scarce resource"? > +After defining a global register variable, for the duration of > +the current compilation: It's probably better to say "for the current compilation unit"? There now is LTO and whatnot. > +All global register variable declarations must precede all function > +definitions. If such a declaration appears after function definitions, > +the declaration would be too late to prevent the register from being used > +for other purposes in the preceding functions. This isn't true anymore, not even with -fno-toplevel-reorder or -O0. > +When selecting a register, choose one that is normally saved and > +restored by function calls on your machine. This ensures that code > +which is unaware of this reservation (such as library routines) will > +restore it before returning. The compiler also warns, possibly for the unlikely case that the user has not read the documentation. Thanks, Segher
