On 2/8/22 16:59, Martin Sebor wrote:
Transforming a by-value arguments to by-reference as GCC does for some
class types can trigger -Wdangling-pointer when the argument is used
to store the address of a local variable. Since the stored value is
not accessible in the caller the warning is a false positive.
The attached patch handles this case by excluding PARM_DECLs with
the DECL_BY_REFERENCE bit set from consideration.
While testing the patch I noticed some instances of the warning are
uninitentionally duplicated as the pass runs more than once. To avoid
that, I also introduce warning suppression into the handler for this
instance of the warning. (There might still be others.)
The second test should verify that we do warn about returning 't' from a
function; we don't want to ignore the DECL_BY_REFERENCE RESULT_DECL.
+ tree var = SSA_NAME_VAR (lhs_ref.ref);
+ if (DECL_BY_REFERENCE (var))
+ /* Avoid by-value arguments transformed into by-reference. */
+ continue;
I wonder if we can we express this property of invisiref parms somewhere
more general? I imagine optimizations would find it useful as well.
Could pointer_query somehow treat the reference as pointing to a
function-local object?
I previously tried to express this by marking the reference as
'restrict', but that was wrong
(https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97474).
Jason
