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| author | Jakub Jelinek <jakub@redhat.com> | 2021-10-19 09:24:57 +0200 |
|---|---|---|
| committer | Jakub Jelinek <jakub@redhat.com> | 2021-10-19 09:24:57 +0200 |
| commit | f45610a45236e97616726ca042898d6ac46a082e (patch) | |
| tree | 766d47e11fff8bea1ceab16e2ce4c35dc6ceb9e2 | |
| parent | caab0139761b04226fab14d87c4a4f981d942bbf (diff) | |
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c++: Don't reject calls through PMF during constant evaluation [PR102786]
The following testcase incorrectly rejects the c initializer,
while in the s.*a case cxx_eval_* sees .__pfn reads etc.,
in the s.*&S::foo case get_member_function_from_ptrfunc creates
expressions which use INTEGER_CSTs with type of pointer to METHOD_TYPE.
And cxx_eval_constant_expression rejects any INTEGER_CSTs with pointer
type if they aren't 0.
Either we'd need to make sure we defer such folding till cp_fold but the
function and pfn_from_ptrmemfunc is used from lots of places, or
the following patch just tries to reject only non-zero INTEGER_CSTs
with pointer types if they don't point to METHOD_TYPE in the hope that
all such INTEGER_CSTs with POINTER_TYPE to METHOD_TYPE are result of
folding valid pointer-to-member function expressions.
I don't immediately see how one could create such INTEGER_CSTs otherwise,
cast of integers to PMF is rejected and would have the PMF RECORD_TYPE
anyway, etc.
2021-10-19 Jakub Jelinek <jakub@redhat.com>
PR c++/102786
* constexpr.c (cxx_eval_constant_expression): Don't reject
INTEGER_CSTs with type POINTER_TYPE to METHOD_TYPE.
* g++.dg/cpp2a/constexpr-virtual19.C: New test.
| -rw-r--r-- | gcc/cp/constexpr.c | 4 | ||||
| -rw-r--r-- | gcc/testsuite/g++.dg/cpp2a/constexpr-virtual19.C | 11 |
2 files changed, 15 insertions, 0 deletions
diff --git a/gcc/cp/constexpr.c b/gcc/cp/constexpr.c index c5f01b9..6f83d30 100644 --- a/gcc/cp/constexpr.c +++ b/gcc/cp/constexpr.c @@ -6191,6 +6191,10 @@ cxx_eval_constant_expression (const constexpr_ctx *ctx, tree t, if (TREE_CODE (t) == INTEGER_CST && TYPE_PTR_P (TREE_TYPE (t)) + /* INTEGER_CST with pointer-to-method type is only used + for a virtual method in a pointer to member function. + Don't reject those. */ + && TREE_CODE (TREE_TYPE (TREE_TYPE (t))) != METHOD_TYPE && !integer_zerop (t)) { if (!ctx->quiet) diff --git a/gcc/testsuite/g++.dg/cpp2a/constexpr-virtual19.C b/gcc/testsuite/g++.dg/cpp2a/constexpr-virtual19.C new file mode 100644 index 0000000..cb0d1be --- /dev/null +++ b/gcc/testsuite/g++.dg/cpp2a/constexpr-virtual19.C @@ -0,0 +1,11 @@ +// PR c++/102786 +// { dg-do compile { target c++20 } } + +struct S { + virtual constexpr int foo () const { return 42; } +}; + +constexpr S s; +constexpr auto a = &S::foo; +constexpr auto b = (s.*a) (); +constexpr auto c = (s.*&S::foo) (); |