RFR: 8295159: DSO created with -ffast-math breaks Java floating-point arithmetic

[Andrew Haley]

On Tue, 11 Oct 2022 16:02:41 GMT, Andrew Haley <aph at 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.

Also: this patch is Linux-only. I'll ask for help from build experts to make the tests GCC-only; it's not clear to me how.

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PR: https://git.openjdk.org/jdk/pull/10661