https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115770
Manuel Köppen <manuel.koeppen at gmx dot de> changed:
What |Removed |Added
----------------------------------------------------------------------------
Resolution|INVALID |FIXED
--- Comment #5 from Manuel Köppen <manuel.koeppen at gmx dot de> ---
Even if something is "undefined", the compiler should not output broken code,
without any warning (nothing, even with -pedantic).
The optimizer is optimizing out my perfectly fine asm volatile block, just
because it thinks the value passed to it is undefined? Then he replaces it with
an invalid instruction. I struggle to even call this an optimization!
The standard does not actually define reading memory at address 0 as undefined,
because NULL and 0 don't necessarily need to be the same (athough they almost
always are).
To the very least, there should be a warning like
Warning: Intentionally inserted invalid opcode (use of potentially undefined
value).
Following your argumentation, when an undefined value from stack is used, also
this udf opcode should be inserted, to be consistent.
