+cc libc-alpha On Mon, Mar 18, 2013 at 9:05 AM, Xinliang David Li <davi...@google.com> wrote: > Interesting idea about lazy IFUNC relocation.
> On Mon, Mar 18, 2013 at 2:02 AM, Richard Biener > <richard.guent...@gmail.com> wrote: >> On Fri, Mar 15, 2013 at 10:55 PM, Sriraman Tallam <tmsri...@google.com> >> wrote: >>> This patch is meant for google/gcc-4_7 but I want this to be >>> considered for trunk when it opens again. This patch makes it easy to >>> test for code coverage of multiversioned functions. Here is a >>> motivating example: >> Err. As we are using IFUNCs isn't it simply possible to do this in >> the dynamic loader - for example by simlply pre-loading a library >> with the IFUNC relocators implemented differently? Thus, shouldn't >> we simply provide such library as a convenience? A similar need exists in glibc itself: it too has multiversioned functions, and lack of testing has led to recent bugs in some of them. HJ has added a framework to test IFUNCs to glibc late last year, but it would be nice to have a more general IFUNC control, so I could e.g. run a binary on SSE4-capable machine A as that binary would run on SSE2-only capable machine B. (We've had a few bugs recently, were the crash would only show on machine B and not A. These are a pain to debug, as I may not have access to B.) If such a controller is implemented, I'd think it would have to be part of GLIBC (or part of the ld-linux itself), and not of libgcc. LD_CPU_FEATURES=sse,sse2 ./a.out # run as if only sse and sse2 are available Thanks, -- Paul Pluzhnikov
