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c++: fix ICE in joust_maybe_elide_copy [PR106675]

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joust_maybe_elide_copy checks that the last conversion in the ICS for
the first argument is ck_ref_bind, which is reasonable, because we've
checked that we're dealing with a copy/move constructor.  But it can
also happen that we couldn't figure out which conversion function is
better to convert the argument, as in this testcase: joust couldn't
decide if we should go with

  operator foo &()

or

  operator foo const &()

so we get a ck_ambig, which then upsets joust_maybe_elide_copy.  Since
a ck_ambig can validly occur, I think we should just return early, as
in the patch below.

	PR c++/106675

gcc/cp/ChangeLog:

	* call.cc (joust_maybe_elide_copy): Return false for ck_ambig.

gcc/testsuite/ChangeLog:

	* g++.dg/cpp0x/overload-conv-5.C: New test.
This commit is contained in:
Marek Polacek 2023-02-10 17:26:57 -05:00
parent c348a71721
commit cce6262502
2 changed files with 23 additions and 0 deletions
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2
gcc/cp/call.cc
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@ -12542,6 +12542,8 @@ joust_maybe_elide_copy (z_candidate *&cand)
if (!DECL_COPY_CONSTRUCTOR_P (fn) && !DECL_MOVE_CONSTRUCTOR_P (fn))
return false;
conversion *conv = cand->convs[0];
if (conv->kind == ck_ambig)
return false;
gcc_checking_assert (conv->kind == ck_ref_bind);
conv = next_conversion (conv);
if (conv->kind == ck_user && !TYPE_REF_P (conv->type))

21
gcc/testsuite/g++.dg/cpp0x/overload-conv-5.C Normal file
View file

@ -0,0 +1,21 @@
// PR c++/106675
// { dg-do compile { target c++11 } }
struct foo {
int n_;
foo(int n) : n_(n) {}
};
struct bar {
int n_;
operator foo() const {
return foo(n_);
}
operator foo &() { return *reinterpret_cast<foo *>(n_); }
operator foo const &() = delete;
void crashgcc() {
foo tmp(*this); // { dg-error "ambiguous" }
}
};