https://gcc.gnu.org/g:7fed7e9bbc57d502e141e079a6be2706bdbd4560
commit r15-1292-g7fed7e9bbc57d502e141e079a6be2706bdbd4560
Author: Patrick Palka <ppa...@redhat.com>
Date: Thu Jun 13 10:02:43 2024 -0400
c++: ICE w/ ambig and non-strictly-viable cands [PR115239]
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 second arg conversion since the first arg conversion was deemed
bad, and this trips up joust when called on #3 and #4 which assumes all
arg conversions are there.
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.
Reviewed-by: Jason Merrill <ja...@redhat.com>
Diff:
---
gcc/cp/call.cc | 3 ++-
gcc/testsuite/g++.dg/overload/error7.C | 10 ++++++++++
2 files changed, 12 insertions(+), 1 deletion(-)
diff --git a/gcc/cp/call.cc b/gcc/cp/call.cc
index 85536fc25ff2..7bbc1fb0c789 100644
--- a/gcc/cp/call.cc
+++ b/gcc/cp/call.cc
@@ -13490,7 +13490,8 @@ tourney (struct z_candidate *candidates, tsubst_flags_t
complain)
{
previous_worse_champ = nullptr;
champ = &(*challenger)->next;
- if (!*champ || !(*champ)->viable)
+ if (!*champ || !(*champ)->viable
+ || (*champ)->viable < (*challenger)->viable)
{
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 000000000000..de50ce5f66e4
--- /dev/null
+++ b/gcc/testsuite/g++.dg/overload/error7.C
@@ -0,0 +1,10 @@
+// PR c++/115239
+
+bool foo(char *, long); // #1, strictly viable, ambig with #2
+bool foo(char *, unsigned); // #2, strictly viable, ambig with #1
+bool foo(char, long); // #3, non-strictly viable
+bool foo(char, unsigned); // #4, non-strictly viable
+
+int main() {
+ foo((char *)0, 0); // { dg-error "ambiguous" }
+}
