Bug 93620

Summary: Floating point is broken in C++ on targets with excess precision
Product: gcc Reporter: Rich Felker <bugdal>
Component: c++Assignee: Not yet assigned to anyone <unassigned>
Status: RESOLVED DUPLICATE    
Severity: normal    
Priority: P3    
Version: unknown   
Target Milestone: ---   
See Also: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=85957
Host: Target:
Build: Known to work:
Known to fail: Last reconfirmed:

Description Rich Felker 2020-02-07 02:35:26 UTC 
Attempting to use -fexcess-precision=standard with g++ produces:

cc1plus: sorry, unimplemented: '-fexcess-precision=standard' for C++

In light of eldritch horrors like pr 85957 this means floating point is essentially catastrophically broken on i386 and m68k.

This came to my attention while analyzing https://github.com/OSGeo/PROJ/issues/1906. Most of the problems are g++ incorrectly handling excess precision, and they're having to put awful hacks with volatile objects in place to work around it.
Comment 1 Andrew Pinski 2020-02-07 02:38:34 UTC 
Yes this is known.  See PR 323.
Where even this is mentioned that C++ is not enabled yet.

*** This bug has been marked as a duplicate of bug 323 ***