Messages in this thread | | | Date | Wed, 2 Oct 2013 08:13:35 +0200 | From | Ingo Molnar <> | Subject | Re: [PATCH] perf: Support for Openembedded/Yocto -dbg packages |
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* Namhyung Kim <namhyung@kernel.org> wrote:
> Hi Ingo and Arnaldo, > > On Wed, 18 Sep 2013 15:29:03 +0200, Ingo Molnar wrote: > > * Arnaldo Carvalho de Melo <acme@ghostprotocols.net> wrote: > > > >> Em Wed, Sep 18, 2013 at 12:18:01PM +0200, Peter Zijlstra escreveu: > >> > On Wed, Sep 18, 2013 at 12:02:12PM +0200, Ricardo Ribalda Delgado wrote: > >> > > Perhaps this is even more clear than v2: > >> > >> > > len = snprintf(file, size, "%s", symbol_conf.symfs); > >> > > size -= len; > >> > > file += len; > >> > > len = snprintf(file, MIN(size,(last_slash - dso->long_name) + 2), > >> > > "%s", dso->long_name); > >> > > size -= len; > >> > > file += len; > >> > > len = snprintf(file, size, ".debug%s", last_slash); > >> > >> > len = 0; > >> > >> > len += snprintf(str + len, size - len, ...); > >> > len += snprintf(str + len, size - len, ...); > >> > >> And avoid snprintf like the plague, use scnprintf instead... See > >> e7f01d1e3d8d501deb8abeaa269d5d48a703b8b0 for details :-) > > > > Hm, could we do: > > > > #define snprintf scnprintf > > > > or: > > > > #define snprintf(x...) BUILD_BUG() > > > > ? > > > > I don't think there's any valid code, except printf wrappers (which we > > don't have in perf), where the semantics of snprintf() would be needed. > > There are some places that use snprintf() to query the actual length: > > tools/perf/util/srcline.c:245: size = snprintf(NULL, 0, "%s:%u", file, line) + 1; > tools/perf/util/values.c:147: width = snprintf(NULL, 0, "%d", values->pid[i]); > tools/perf/util/values.c:150: width = snprintf(NULL, 0, "%d", values->tid[i]); > tools/perf/util/values.c:154: width = snprintf(NULL, 0, "%" PRIu64, values->value[i][j]); > tools/perf/util/values.c:189: width = snprintf(NULL, 0, "%d", values->pid[i]); > tools/perf/util/values.c:192: width = snprintf(NULL, 0, "%d", values->tid[i]); > tools/perf/util/values.c:200: width = snprintf(NULL, 0, "%" PRIx64, values->counterrawid[j]); > tools/perf/util/values.c:206: width = snprintf(NULL, 0, "%" PRIu64, values->value[i][j]);
I think that should be a separate, more obviously named helper inline instead, something like:
static inline printf_width(const char *fmt, ...) { va_list args; int width;
va_start(args, fmt); width = vsnprintf(NULL, 0, fmt, args); va_end(args);
return width; }
#define snprintf(fmt...) BUILD_BUG_ON(1, "Use scnprintf() instead of snprintf()")
or so? Then we could use it like this:
> tools/perf/util/values.c:147: width = printf_width("%d", values->pid[i]);
and naked snprintf use would provoke a build bug.
Various printf wrappers can still use vsnprintf() - it's the routine use of snprintf() instead of scnprintf() that should be inhibited.
Thanks,
Ingo
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