On Thu, Jun 14, 2018 at 12:35 AM Martin Sebor <mse...@gmail.com> wrote: > > The C implementation of the -Wbuiltin-declaration-mismatch > warning relies on TYPE_MODE to detect incompatibilities > between return and argument types in user declarations of > built-in functions. That prevents mistakes like > > char* strlen (const char*); > > from being detected (where sizeof (char*) == sizeof (size_t)), > while at the same diagnosing similar bugs such as > > char* strcmp (const char*, const char*); > > where sizeof (char*) != sizeof (int), and always diagnosing > benign declarations like: > > void strcpy (char*, const char*) > > The attached patch tightens up the detection of incompatible > types so that when -Wextra is set it diagnoses more of these > kinds of problems, including mismatches in qualifiers. (I > added this under -Wextra mainly to avoid the warning with > just -Wall for some of the more benign incompatibilities > like those in const-qualifiers). > > This enhancement was prompted by bug 86114. As it is, it > would not have prevented the ICE in that bug because it does > not reject the incompatible redeclaration (I did that to keep > compatibility with prior GCC versions). If there is support > for it, though, I think rejecting all incompatible declarations > would be a better solution. Partly because the middle-end > doesn't seem to fully consider incompatible return types and > so might end up introducing transformations that don't make > sense. And partly because I think at least the C and POSIX > standard built-in functions should be declared with > the types they are specified.
Why not go the simpler way of doing || POINTER_TYPE_P (oldrettype) != POINTER_TYPE_P (newrettype) after the mode check? I don't think a mismatch in pointer vs. non-pointer was a desired loophole. Richard. > Martin
