https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100404
Richard Biener <rguenth at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Last reconfirmed| |2021-05-04
Ever confirmed|0 |1
Severity|normal |enhancement
Status|UNCONFIRMED |NEW
--- Comment #3 from Richard Biener <rguenth at gcc dot gnu.org> ---
Hmm, OK, looks like -fno-delete-null-pointer-checks doesn't cover nonnull
marked pointers even if that's not obvious. Quoting:
@item -fdelete-null-pointer-checks
@opindex fdelete-null-pointer-checks
Assume that programs cannot safely dereference null pointers, and that
no code or data element resides at address zero.
This option enables simple constant
folding optimizations at all optimization levels. In addition, other
optimization passes in GCC use this flag to control global dataflow
analyses that eliminate useless checks for null pointers; these assume
that a memory access to address zero always results in a trap, so
that if a pointer is checked after it has already been dereferenced,
it cannot be null.
Note however that in some environments this assumption is not true.
Use @option{-fno-delete-null-pointer-checks} to disable this optimization
for programs that depend on that behavior.
This option is enabled by default on most targets. On Nios II ELF, it
defaults to off. On AVR, CR16, and MSP430, this option is completely disabled.
Passes that use the dataflow information
are enabled independently at different optimization levels.
it might be possible to enhance this, but there seem to be multiple spots
in the compiler that would need adjusting.
