> On Sep 28, 2020, at 11:13 AM, Eric Liu <eric.c....@arm.com> wrote: > > Hi, > > Thanks for looking at this. > > For gcc-10, it's hard to make 'strncpy' all right with asan enabled > (approaches we talked previous don't work). > I'm trying to find a better way to avoid using compile pragma. I suppose it > would be better to use 'memcpy' > to replace 'strncpy'. > > > Thanks, > Eric
I don't think using memory functions in place of string functions for string manipulation is really an improvement. I did a bit of experimenting. With gcc10.2, and using the --enable-asan configure option, we get a -Wstringop-truncation warning in CompilerCounters::set_current_method, even after careful adjustment of the code to use the documented idiom for avoiding that warning. I initially wondered whether this might be only in fastdebug builds, where we also define _FORTIFY_SOURCE=2. The asan faq https://github.com/google/sanitizers/wiki/AddressSanitizer#faq says asan doesn't work well with _FORTIFY_SOURCE. But the same warning occurs in a release build, where we aren't defining _FORTIFY_SOURCE. At this point all I can conclude is that --enable-asan (i.e. -fsanitize=address) is simply incompatible with -Wstringop-truncation, at least through gcc10. That seems like a bug that someone should report. (Might be same as or related to https://gcc.gnu.org/bugzilla/show_bug.cgi?id=85650) We don't normally build with -fsanitize=address; that's something that someone might want to turn on sometimes for testing or debugging, but I don't think we're planning to have it always on, even in debug builds. Since it seems to be incompatible with various other options that we *do* normally use, I think the way to allow --enable-asan to be (possibly) usable is in the build system at configure time. That is, the --enable-asan configure option should, in addition to adding -fsanitize=address, also (1) disable -Wstringop-truncation and (2) disable the defining of _FORTIFY_SOURCE in fastdebug builds. It looks like making those changes involves conditionalizing their addition/removal using ${ASAN_ENABLED}. Scattering pragmas for disabling -Wstringop-truncation doesn't cut it.
