On Wed, 24 Jan 2024 09:29:16 GMT, Andrew Haley <a...@openjdk.org> wrote:
> > > I think you should be able to use ld and objcopy to merge the .o files > > > and hide all of the symbols you don't want to export. > > > > > > We also discussed about `objcopy` in [#14808 > > (comment)](https://github.com/openjdk/jdk/pull/14808#issuecomment-1631597197) > > and [#14808 > > (comment)](https://github.com/openjdk/jdk/pull/14808#issuecomment-1631611220). > > My main concern was the portability of `objcopy` approach. > > I replied: > > OK, but it is the right thing to do on Linux. If some other operating systems > don't provide useful tools, that's on them. I haven't checked, but I strongly > suspect that LLVM can do it too, so all that remains is Windows, and maybe > they can't have static linking (or maybe they have to use something like this > PR) until the right tooling is provided. > > If Windows really can't do it, that's no reason to burden systems that can. > Namespaces are not a low-cost solution for developers. Thanks, @theRealAph. Yeah, I was mainly concerned about non-unix like systems, Windows particularly. It might not work on all potentially supported compilers (`gcc`) on linux, however. To localizing symbols in `libjvm` using `objcopy`, we can first partially link (with `-r`) all hotspot `.o` into a single object file, then run `objcopy` for the output object file to localize the affected symbols. The partial linking work (https://github.com/openjdk/jdk/blob/2003610b3b52eed04de6713a2a36151d0d86d7c9/make/common/NativeCompilation.gmk#L1245) has been added already. However, during the https://github.com/openjdk/jdk/pull/14064 work, we ran into issues with partial linking on older `gcc` for linux-aarch64. The details were captured in https://github.com/openjdk/jdk/pull/14064#issuecomment-1564908324 discussion with @erikj79. Only `clang` currently work well with the partial linking and symbol localizing solution. Maybe we could live with symbol redefinition using #define (conditionally for static linking in OpenJDK, as Coleen suggested earlier) for now, until the tooling can support symbol localizing better. Then localizing symbols using tools like `objcopy` can be the longer term and cleaner solution, instead of using namespace. What's your thoughts on that? ------------- PR Comment: https://git.openjdk.org/jdk/pull/17456#issuecomment-1909019550
