On Thu, 26 Oct 2023 14:17:02 GMT, Andrew Haley <a...@openjdk.org> wrote:
>> A bug in GCC causes shared libraries linked with -ffast-math to disable >> denormal arithmetic. This breaks Java's floating-point semantics. >> >> The bug is https://gcc.gnu.org/bugzilla/show_bug.cgi?id=55522 >> >> One solution is to save and restore the floating-point control word around >> System.loadLibrary(). This isn't perfect, because some shared library might >> load another shared library at runtime, but it's a lot better than what we >> do now. >> >> However, this fix is not complete. `dlopen()` is called from many places in >> the JDK. I guess the best thing to do is find and wrap them all. I'd like to >> hear people's opinions. > > Andrew Haley has updated the pull request incrementally with one additional > commit since the last revision: > > Duh This looks good to me. One suggestion: to reduce code duplication and to make the code a bit safer against accidental returns prior to fesetenv, I would have used a mark object like this: struct FenvResetMark { fenv_t _fenv; FenvResetMark() { fegetenv(&_fenv); } ~FenvResetMark() { fesetenv(&_fenv); } }; and would have placed it above dlopen calls. Up to you. --- About the dlopen calls in the JDK, at SAP we were faced with similar problems for other libc APIs (how to apply a fix to all of them). Some of these issues we solved by redirecting all calls to libjvm. Others we solved manually, in-place, with a lot of duplication. None of these sound appealing, but I like the redirect-to-libjvm route somewhat, if Oracle can be convinced. A third option would be to use an interposition library with LD_PRELOAD. One that overwrites dlopen and redirects to the real one. I don't see this to be a practical solution but it may be valid for testing. ------------- Marked as reviewed by stuefe (Reviewer). PR Review: https://git.openjdk.org/jdk/pull/10661#pullrequestreview-1699974743
