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author | Patrick Palka <ppalka@redhat.com> | 2024-01-03 15:43:28 -0500 |
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committer | Patrick Palka <ppalka@redhat.com> | 2024-01-03 15:43:28 -0500 |
commit | 1c522c9eafa5b86b78cd7b3044e120762fb4c879 (patch) | |
tree | 7e1a70038ed7a24173838edae6c0c37edad0155a /gcc/cp | |
parent | 93c96e3ad0024a397115aa17bf29c7efc6b535a1 (diff) | |
download | gcc-1c522c9eafa5b86b78cd7b3044e120762fb4c879.zip gcc-1c522c9eafa5b86b78cd7b3044e120762fb4c879.tar.gz gcc-1c522c9eafa5b86b78cd7b3044e120762fb4c879.tar.bz2 |
c++: bad direct reference binding via conv fn [PR113064]
When computing a direct reference binding via a conversion function
yields a bad conversion, reference_binding incorrectly commits to that
conversion instead of trying a conversion via a temporary. This causes
us to reject the first testcase because the bad direct conversion to B&&
via the && conversion operator prevents us from considering the good
conversion via the & conversion operator and a temporary. (Similar
story for the second testcase.)
This patch fixes this by making reference_binding not prematurely commit
to such a bad direct conversion. We still fall back to it if using a
temporary also fails (otherwise the diagnostic for cpp0x/explicit7.C
regresses).
PR c++/113064
gcc/cp/ChangeLog:
* call.cc (reference_binding): Still try a conversion via a
temporary if a direct conversion was bad.
gcc/testsuite/ChangeLog:
* g++.dg/cpp0x/rv-conv4.C: New test.
* g++.dg/cpp0x/rv-conv5.C: New test.
Diffstat (limited to 'gcc/cp')
-rw-r--r-- | gcc/cp/call.cc | 22 |
1 files changed, 18 insertions, 4 deletions
diff --git a/gcc/cp/call.cc b/gcc/cp/call.cc index d9ddd36..1c67572 100644 --- a/gcc/cp/call.cc +++ b/gcc/cp/call.cc @@ -1739,6 +1739,7 @@ reference_binding (tree rto, tree rfrom, tree expr, bool c_cast_p, int flags, tsubst_flags_t complain) { conversion *conv = NULL; + conversion *bad_direct_conv = nullptr; tree to = TREE_TYPE (rto); tree from = rfrom; tree tfrom; @@ -1925,13 +1926,23 @@ reference_binding (tree rto, tree rfrom, tree expr, bool c_cast_p, int flags, z_candidate *cand = build_user_type_conversion_1 (rto, expr, flags, complain); if (cand) - return cand->second_conv; + { + if (!cand->second_conv->bad_p) + return cand->second_conv; + + /* Direct reference binding wasn't successful and yielded a bad + conversion. Proceed with trying to go through a temporary + instead, and if that also fails then we'll return this bad + conversion rather than no conversion for sake of better + diagnostics. */ + bad_direct_conv = cand->second_conv; + } } /* From this point on, we conceptually need temporaries, even if we elide them. Only the cases above are "direct bindings". */ if (flags & LOOKUP_NO_TEMP_BIND) - return NULL; + return bad_direct_conv ? bad_direct_conv : nullptr; /* [over.ics.rank] @@ -1972,6 +1983,9 @@ reference_binding (tree rto, tree rfrom, tree expr, bool c_cast_p, int flags, there's no strictly viable candidate. */ if (!maybe_valid_p && (flags & LOOKUP_SHORTCUT_BAD_CONVS)) { + if (bad_direct_conv) + return bad_direct_conv; + conv = alloc_conversion (ck_deferred_bad); conv->bad_p = true; return conv; @@ -1995,7 +2009,7 @@ reference_binding (tree rto, tree rfrom, tree expr, bool c_cast_p, int flags, conv = implicit_conversion (to, from, expr, c_cast_p, flags, complain); if (!conv) - return NULL; + return bad_direct_conv ? bad_direct_conv : nullptr; if (conv->user_conv_p) { @@ -2018,7 +2032,7 @@ reference_binding (tree rto, tree rfrom, tree expr, bool c_cast_p, int flags, = reference_binding (rto, ftype, NULL_TREE, c_cast_p, sflags, complain); if (!new_second) - return NULL; + return bad_direct_conv ? bad_direct_conv : nullptr; conv = merge_conversion_sequences (t, new_second); gcc_assert (maybe_valid_p || conv->bad_p); return conv; |