On 4/30/19 8:12 PM, Rich Felker wrote: >>> What are you trying to achieve? I was just CC'd and I'm missing the >>> context. >> >> Sorry I added you as a subject matter expert but didn't provide enough context. >> >> The original issue [1] was perf failing to build on ARC due to perf tools needing >> a copy of unistd.h but this thread [2] was a small side issue of auto-detecting >> libc variaint in perf tools where despite uClibc tools, glibc is declared to be >> detected, due to uClibc's historical hack of defining __GLIBC__. So __GLIBC__ is >> not sufficient (and probably not the right interface to begin wtih) to ensure glibc. >> >> [1] http://lists.infradead.org/pipermail/linux-snps-arc/2019-April/005676.html >> [2] http://lists.infradead.org/pipermail/linux-snps-arc/2019-April/005684.html > > I think you misunderstood -- :-) > I'm asking what you're trying to achieve > by detecting whether the libc is glibc, rather than whether it has > some particular interface you want to conditionally use. This is a > major smell and is usually something wrong that shouldn't be done. Good question indeed. Back in 2015 I initially ran into some quirks due to subtle libc differences. At the time perf has a fwd ref for strlcpy which exactly matched glibc but not uClibc. see commit a83d869f300bf91 "(perf tools: Elide strlcpy warning with uclibc)" or 0215d59b154 "(tools lib: Reinstate strlcpy() header guard with __UCLIBC__)" But this still used the libc defined symbol __UCLIBC__ or __GLIBC__ Your question however pertains to perf glibc feature check where perf generates an alternate symbol HAVE_GLIBC_SUPPORT. This is dubious as first of all it detects glibc even for uClibc builds. Even of we were to improve it, there seems to be no users of this symbol. $git grep HAVE_GLIBC_SUPPORT perf/Makefile.config: CFLAGS += -DHAVE_GLIBC_SUPPORT perf/builtin-version.c: STATUS(HAVE_GLIBC_SUPPORT, glibc) So I'd propose to remove it ! _______________________________________________ linux-snps-arc mailing list linux-snps-arc@xxxxxxxxxxxxxxxxxxx http://lists.infradead.org/mailman/listinfo/linux-snps-arc
