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| author | Jason Merrill <jason@redhat.com> | 2024-04-10 15:12:26 -0400 |
|---|---|---|
| committer | Jason Merrill <jason@redhat.com> | 2024-04-12 15:34:29 -0400 |
| commit | df7bfdb7dbf2d46aa5768a0280d4dcfcc868b7f9 (patch) | |
| tree | 963ecde0b9cf6971d1cd577d9aacfc03ee3305a3 /gcc/cp | |
| parent | d435571b54b02946c97b5b24f20e5a7058fd96a1 (diff) | |
| download | gcc-df7bfdb7dbf2d46aa5768a0280d4dcfcc868b7f9.zip gcc-df7bfdb7dbf2d46aa5768a0280d4dcfcc868b7f9.tar.gz gcc-df7bfdb7dbf2d46aa5768a0280d4dcfcc868b7f9.tar.bz2 | |
c++: reference cast, conversion fn [PR113141]
The second testcase in 113141 is a separate issue: we first decide that the
conversion is ill-formed, but then when recalculating the special c_cast_p
handling makes us think it's OK. We don't want that, it should continue to
fall back to the reinterpret_cast interpretation. And while we're here,
let's warn that we're not using the conversion function.
Note that the standard seems to say that in this case we should
treat (Matrix &) as const_cast<Matrix &>(static_cast<const Matrix &>(X)),
which would use the conversion operator, but that doesn't match existing
practice, so let's resolve that another day. I've raised this issue with
CWG; at the moment I lean toward never binding a temporary in a C-style cast
to reference type, which would also be a change from existing practice.
PR c++/113141
gcc/c-family/ChangeLog:
* c.opt: Add -Wcast-user-defined.
gcc/ChangeLog:
* doc/invoke.texi: Document -Wcast-user-defined.
gcc/cp/ChangeLog:
* call.cc (reference_binding): For an invalid cast, warn and don't
recalculate.
gcc/testsuite/ChangeLog:
* g++.dg/conversion/ref12.C: New test.
Co-authored-by: Patrick Palka <ppalka@redhat.com>
Diffstat (limited to 'gcc/cp')
| -rw-r--r-- | gcc/cp/call.cc | 12 |
1 files changed, 11 insertions, 1 deletions
diff --git a/gcc/cp/call.cc b/gcc/cp/call.cc index 15b5647..dbdd7c2 100644 --- a/gcc/cp/call.cc +++ b/gcc/cp/call.cc @@ -2034,7 +2034,17 @@ reference_binding (tree rto, tree rfrom, tree expr, bool c_cast_p, int flags, recalculate the second conversion sequence. */ for (conversion *t = conv; t; t = next_conversion (t)) if (t->kind == ck_user - && DECL_CONV_FN_P (t->cand->fn)) + && c_cast_p && !maybe_valid_p) + { + if (complain & tf_warning) + warning (OPT_Wcast_user_defined, + "casting %qT to %qT does not use %qD", + from, rto, t->cand->fn); + /* Don't let recalculation try to make this valid. */ + break; + } + else if (t->kind == ck_user + && DECL_CONV_FN_P (t->cand->fn)) { tree ftype = TREE_TYPE (TREE_TYPE (t->cand->fn)); /* A prvalue of non-class type is cv-unqualified. */ |