| Message ID | 20231115180350.2126787-1-ppalka@redhat.com |
|---|---|
| State | New |
| Headers | show |
| Series | c++: constantness of call to function pointer [PR111703] | expand |
On 11/15/23 13:03, Patrick Palka wrote: > Bootstrapped and regtested on x86_64-pc-linux-gnu, does this look OK > for trunk/13/12 (to match the PR107939 / r13-6525-ge09bc034d1b4d6 backports)? > > -- >8 -- > > potential_constant_expression for a CALL_EXPR to a non-overload tests > FUNCTION_POINTER_TYPE_P on the callee rather than on the type of the > callee, which means we always pass want_rval=any when recursing and so > may fail to properly treat a non-constant function pointer callee as such. > Fixing this turns out to further work around the PR111703 issue. > > PR c++/111703 > PR c++/107939 > > gcc/cp/ChangeLog: > > * constexpr.cc (potential_constant_expression_1) <case CALL_EXPR>: > Fix FUNCTION_POINTER_TYPE_P test. > > gcc/testsuite/ChangeLog: > > * g++.dg/cpp2a/concepts-fn8.C: Extend test. > * g++.dg/diagnostic/constexpr4.C: New test. > --- > gcc/cp/constexpr.cc | 4 +++- > gcc/testsuite/g++.dg/cpp2a/concepts-fn8.C | 2 ++ > gcc/testsuite/g++.dg/diagnostic/constexpr4.C | 9 +++++++++ > 3 files changed, 14 insertions(+), 1 deletion(-) > create mode 100644 gcc/testsuite/g++.dg/diagnostic/constexpr4.C > > diff --git a/gcc/cp/constexpr.cc b/gcc/cp/constexpr.cc > index 8a6b210144a..5ecc30117a1 100644 > --- a/gcc/cp/constexpr.cc > +++ b/gcc/cp/constexpr.cc > @@ -9547,7 +9547,9 @@ potential_constant_expression_1 (tree t, bool want_rval, bool strict, bool now, > } > else if (fun) > { > - if (RECUR (fun, FUNCTION_POINTER_TYPE_P (fun) ? rval : any)) > + if (RECUR (fun, (TREE_TYPE (fun) > + && FUNCTION_POINTER_TYPE_P (TREE_TYPE (fun)) > + ? rval : any))) We might break this ?: out into a variable? OK either way. > /* Might end up being a constant function pointer. But it > could also be a function object with constexpr op(), so > we pass 'any' so that the underlying VAR_DECL is deemed > diff --git a/gcc/testsuite/g++.dg/cpp2a/concepts-fn8.C b/gcc/testsuite/g++.dg/cpp2a/concepts-fn8.C > index 3f63a5b28d7..c63d26c931d 100644 > --- a/gcc/testsuite/g++.dg/cpp2a/concepts-fn8.C > +++ b/gcc/testsuite/g++.dg/cpp2a/concepts-fn8.C > @@ -15,10 +15,12 @@ struct P { > }; > > void (*f)(P); > +P (*h)(P); > > template<class T> > constexpr bool g() { > P x; > f(x); // { dg-bogus "from here" } > + f(h(x)); // { dg-bogus "from here" } > return true; > } > diff --git a/gcc/testsuite/g++.dg/diagnostic/constexpr4.C b/gcc/testsuite/g++.dg/diagnostic/constexpr4.C > new file mode 100644 > index 00000000000..f971f533b08 > --- /dev/null > +++ b/gcc/testsuite/g++.dg/diagnostic/constexpr4.C > @@ -0,0 +1,9 @@ > +// Verify we diagnose a call to a non-constant function pointer ahead of time. > +// { dg-do compile { target c++11 } } > + > +int (*f)(int); > + > +template<int N> > +void g() { > + static_assert(f(N) == 0, ""); // { dg-error "non-constant|'f' is not usable" } > +}
diff --git a/gcc/cp/constexpr.cc b/gcc/cp/constexpr.cc index 8a6b210144a..5ecc30117a1 100644 --- a/gcc/cp/constexpr.cc +++ b/gcc/cp/constexpr.cc @@ -9547,7 +9547,9 @@ potential_constant_expression_1 (tree t, bool want_rval, bool strict, bool now, } else if (fun) { - if (RECUR (fun, FUNCTION_POINTER_TYPE_P (fun) ? rval : any)) + if (RECUR (fun, (TREE_TYPE (fun) + && FUNCTION_POINTER_TYPE_P (TREE_TYPE (fun)) + ? rval : any))) /* Might end up being a constant function pointer. But it could also be a function object with constexpr op(), so we pass 'any' so that the underlying VAR_DECL is deemed diff --git a/gcc/testsuite/g++.dg/cpp2a/concepts-fn8.C b/gcc/testsuite/g++.dg/cpp2a/concepts-fn8.C index 3f63a5b28d7..c63d26c931d 100644 --- a/gcc/testsuite/g++.dg/cpp2a/concepts-fn8.C +++ b/gcc/testsuite/g++.dg/cpp2a/concepts-fn8.C @@ -15,10 +15,12 @@ struct P { }; void (*f)(P); +P (*h)(P); template<class T> constexpr bool g() { P x; f(x); // { dg-bogus "from here" } + f(h(x)); // { dg-bogus "from here" } return true; } diff --git a/gcc/testsuite/g++.dg/diagnostic/constexpr4.C b/gcc/testsuite/g++.dg/diagnostic/constexpr4.C new file mode 100644 index 00000000000..f971f533b08 --- /dev/null +++ b/gcc/testsuite/g++.dg/diagnostic/constexpr4.C @@ -0,0 +1,9 @@ +// Verify we diagnose a call to a non-constant function pointer ahead of time. +// { dg-do compile { target c++11 } } + +int (*f)(int); + +template<int N> +void g() { + static_assert(f(N) == 0, ""); // { dg-error "non-constant|'f' is not usable" } +}