From: Patrick Palka <ppalka@redhat.com>
To: gcc-patches@gcc.gnu.org
Cc: jason@redhat.com, Patrick Palka <ppalka@redhat.com>
Subject: [PATCH] c++: ICE w/ ambig and non-strictly-viable cands [PR115239]
Date: Wed, 12 Jun 2024 13:56:37 -0400 [thread overview]
Message-ID: <20240612175637.2714077-1-ppalka@redhat.com> (raw)
Bootstrapped and regtested on x86_64-pc-linux-gnu, does this look OK for
trunk/14?
-- >8 --
Here during overload resolution we have two strictly viable ambiguous
candidates #1 and #2, and two non-strictly viable candidates #3 and #4
which we hold on to ever since r14-6522. These latter candidates have
an empty third arg conversion since the second arg conversion was deemed
bad. This ends up causing an ICE during joust for #3 and #4 due to this
empty arg conversion.
We can fix this by making joust robust to empty arg conversions, but in
this situation we shouldn't need to compare #3 and #4 at all given that
we have a strictly viable candidate. To that end, this patch makes
tourney shortcut considering non-strictly viable candidates upon
encountering ambiguity between two strictly viable candidates, taking
advantage of the fact that the candidates list is sorted according to
viability via splice_viable.
PR c++/115239
gcc/cp/ChangeLog:
* call.cc (tourney): Don't consider a non-strictly viable
candidate as the champ if there was ambiguity between two
strictly viable candidates.
gcc/testsuite/ChangeLog:
* g++.dg/overload/error7.C: New test.
---
gcc/cp/call.cc | 4 +++-
gcc/testsuite/g++.dg/overload/error7.C | 10 ++++++++++
2 files changed, 13 insertions(+), 1 deletion(-)
create mode 100644 gcc/testsuite/g++.dg/overload/error7.C
diff --git a/gcc/cp/call.cc b/gcc/cp/call.cc
index ed68eb3c568..82c70f5c39f 100644
--- a/gcc/cp/call.cc
+++ b/gcc/cp/call.cc
@@ -13484,9 +13484,11 @@ tourney (struct z_candidate *candidates, tsubst_flags_t complain)
}
else
{
+ z_candidate *prev_champ = *champ;
previous_worse_champ = nullptr;
champ = &(*challenger)->next;
- if (!*champ || !(*champ)->viable)
+ if (!*champ || !(*champ)->viable
+ || (prev_champ->viable == 1 && (*champ)->viable == -1))
{
champ = nullptr;
break;
diff --git a/gcc/testsuite/g++.dg/overload/error7.C b/gcc/testsuite/g++.dg/overload/error7.C
new file mode 100644
index 00000000000..68aaa236de4
--- /dev/null
+++ b/gcc/testsuite/g++.dg/overload/error7.C
@@ -0,0 +1,10 @@
+// PR c++/115239
+
+bool foo(const char *, char *, long); // #1, strictly viable, ambig with #2
+bool foo(const char *, char *, unsigned); // #2, strictly viable, ambig with #1
+bool foo(char, char, long); // #3, non-strictly viable
+bool foo(char, char, unsigned); // #4, non-strictly viable
+
+int main() {
+ foo((char *)0, (char *)0, 0); // { dg-error "ambiguous" }
+}
--
2.45.2.457.g8d94cfb545
next reply other threads:[~2024-06-12 17:56 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-06-12 17:56 Patrick Palka [this message]
2024-06-12 17:59 ` Patrick Palka
2024-06-13 3:27 ` Jason Merrill
2024-06-13 14:07 ` Patrick Palka
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