[Bug c/40645] Bus error caused by ldd/std instructions in struct copy.

[dentongosnell at yahoo dot com]

------- Comment #3 from dentongosnell at yahoo dot com  2009-07-04 13:32 -------
(In reply to comment #2)

> 
> > One other thing, there is a flag "-mno-faster-structs" which this page
> > suggests would prevent this sort of ldd/std use
> > (http://gcc.gnu.org/onlinedocs/gcc/SPARC-Options.html).  Unfortunately
> > this flag doesn't seem to make any difference to this case.
> 
> -mno-faster-structs is the default.
> 

If "-mno-faster-structs" is the default, then surely it shouldn't be generating
ldd/std in this case (and assuming the 8-byte alignment for "union myblock"). 
The code it is generating is what I would expect if I passed
"-mfaster-structs", based on the above-mentioned documentation page.

In other words, gcc align_bug.c should give just ld/st pairs, and hence should
work without a bus error.

I think either the compiler or the documentation has a bug!


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=40645