Re: [PATCH v3 14/17] perf: Remove subcmd dependencies on strbuf

Josh Poimboeuf
2015-12-14T18:04:59Z

On Mon, Dec 14, 2015 at 02:50:12PM -0300, Arnaldo Carvalho de Melo wrote:
> Em Mon, Dec 14, 2015 at 10:05:37AM -0600, Josh Poimboeuf escreveu:
> > On Mon, Dec 14, 2015 at 12:44:21PM -0300, Arnaldo Carvalho de Melo wrote:
> > > Em Sun, Dec 13, 2015 at 10:18:14PM -0600, Josh Poimboeuf escreveu:
> > > > Introduce and use new astrcat() and astrcatf() functions which replace
> > > > the strbuf functionality for subcmd.
> > >
> > > <SNIP>
> > >
> > > > diff --git a/tools/perf/util/subcmd-util.h b/tools/perf/util/subcmd-util.h
> > > > new file mode 100644
> > > > index 0000000..98fb9f9
> > > > --- /dev/null
> > > > +++ b/tools/perf/util/subcmd-util.h
> > > > @@ -0,0 +1,24 @@
> > > > +#ifndef __PERF_SUBCMD_UTIL_H
> > > > +#define __PERF_SUBCMD_UTIL_H
> > > > +
> > > > +#include <stdio.h>
> > > > +
> > > > +#define astrcatf(out, fmt, ...) \
> > > > +({ \
> > > > + char *tmp = *(out); \
> > > > + if (asprintf((out), "%s" fmt, tmp ?: "", ## __VA_ARGS__) == -1) \
> > > > + die("asprintf failed"); \
> > > > + free(tmp); \
> > > > +})
> > >
> > > Hey, don't add die() calls, please.
> > >
> > > > +
> > > > +static inline void astrcat(char **out, const char *add)
> > > > +{
> > > > + char *tmp = *out;
> > > > +
> > > > + if (asprintf(out, "%s%s", tmp ?: "", add) == -1)
> > > > + die("asprintf failed");
> > > > +
> > > > + free(tmp);
> > >
> > > Ditto.
> >
> > This replaces strbuf, which also calls die() when allocations fail. So
> > this duplicates the existing die-on-allocation-error functionality and
> > is nothing "new" from my perspective.
> >
> > Do you want me to change all the callers (and callers' callers, etc) of
> > these functions to check for errors?
>
> Fair enough, we could do it later, but yeah, ultimately we should call
> all die() calls.
>
> > > And I think that this should go into tools/include/string.h and
> > > tools/lib/string.c, no?
> >
> > If these functions simply duplicate some of strbuf's functionality and
> > they aren't used outside of libsubcmd then I don't see any reason to do
> > that.
>
> Well, we might as well follow that principle, i.e. as soon as there are
> more users, we move it.
>
> But removing strbuf and using something already in libc or something
> equal or slighly similar to what is in the kernel is something I like to
> have in place.

Ok, so just to clarify, is this patch ok in it's current state or is
there anything you'd like me to change for v4? I didn't see anything
similar to astrcat() or astrcatf() in glibc or in the kernel.

> > > We should try to look at the kernel and try to follow naming, semantics,
> > > etc as much as possible. The kernel doesn't have a astrcat, just
> > > kasprintf() (that is in linux/kernel.h, perhaps because in userland
> > > asprintf is in stdio.h, not in string.h) , wonder how something like
> > > astrcat is done there... Doing some research now.
> >
> > Ok.

--
Josh