[PyROOT] Disable automatic conversion of regular to smart pointers

The automatic conversion of ordinary obejcts to smart pointers is
disabled for PyROOT because it can cause trouble with overload
resolution. If a function has overloads for both ordinary objects and
smart pointers, then the implicit conversion to smart pointers can
result in the smart pointer overload being hit, even though there would
be an overload for the regular object. Since PyROOT didn't have this
feature before 6.32 anyway, disabling it was the safest option.

Closes #15117.

bindings/pyroot/cppyy/CPyCppyy/src/Converters.cxx

@@ -2834,6 +2834,14 @@ bool CPyCppyy::SmartPtrConverter::SetArg(
         return true;
     }
 
+// The automatic conversion of ordinary obejcts to smart pointers is disabled
+// for PyROOT because it can cause trouble with overload resolution. If a
+// function has overloads for both ordinary objects and smart pointers, then
+// the implicit conversion to smart pointers can result in the smart pointer
+// overload being hit, even though there would be an overload for the regular
+// object. Since PyROOT didn't have this feature before 6.32 anyway, disabling
+// it was the safest option.
+#if 0
 // for the case where we have an ordinary object to convert
     if (!pyobj->IsSmart() && Cppyy::IsSubtype(oisa, fUnderlyingType)) {
     // create the relevant smart pointer and make the pyobject "smart"
@@ -2852,6 +2860,7 @@ bool CPyCppyy::SmartPtrConverter::SetArg(
 
         return true;
     }
+#endif
 
 // final option, try mapping pointer types held (TODO: do not allow for non-const ref)
     if (pyobj->IsSmart() && Cppyy::IsSubtype(oisa, fUnderlyingType)) {

bindings/pyroot/cppyy/patches/CPyCppyy-Disable-implicit-conversion-to-smart-ptr.patch

@@ -0,0 +1,49 @@
+From 72df898c30db57c43d4cd3136435f36876596c6a Mon Sep 17 00:00:00 2001
+From: Jonas Rembser <jonas.rembser@cern.ch>
+Date: Thu, 4 Apr 2024 02:07:22 +0200
+Subject: [PATCH] [CPyCppyy] Disable automatic conversion of regular to smart
+ pointers
+
+The automatic conversion of ordinary obejcts to smart pointers is
+disabled for PyROOT because it can cause trouble with overload
+resolution. If a function has overloads for both ordinary objects and
+smart pointers, then the implicit conversion to smart pointers can
+result in the smart pointer overload being hit, even though there would
+be an overload for the regular object. Since PyROOT didn't have this
+feature before 6.32 anyway, disabling it was the safest option.
+
+Closes #15117.
+---
+ bindings/pyroot/cppyy/CPyCppyy/src/Converters.cxx | 9 +++++++++
+ 1 file changed, 9 insertions(+)
+
+diff --git a/bindings/pyroot/cppyy/CPyCppyy/src/Converters.cxx b/bindings/pyroot/cppyy/CPyCppyy/src/Converters.cxx
+index 4ac294745ca..830e504ba12 100644
+--- a/bindings/pyroot/cppyy/CPyCppyy/src/Converters.cxx
++++ b/bindings/pyroot/cppyy/CPyCppyy/src/Converters.cxx
+@@ -2834,6 +2834,14 @@ bool CPyCppyy::SmartPtrConverter::SetArg(
+         return true;
+     }
+
++// The automatic conversion of ordinary obejcts to smart pointers is disabled
++// for PyROOT because it can cause trouble with overload resolution. If a
++// function has overloads for both ordinary objects and smart pointers, then
++// the implicit conversion to smart pointers can result in the smart pointer
++// overload being hit, even though there would be an overload for the regular
++// object. Since PyROOT didn't have this feature before 6.32 anyway, disabling
++// it was the safest option.
++#if 0
+ // for the case where we have an ordinary object to convert
+     if (!pyobj->IsSmart() && Cppyy::IsSubtype(oisa, fUnderlyingType)) {
+     // create the relevant smart pointer and make the pyobject "smart"
+@@ -2852,6 +2860,7 @@ bool CPyCppyy::SmartPtrConverter::SetArg(
+
+         return true;
+     }
++#endif
+
+ // final option, try mapping pointer types held (TODO: do not allow for non-const ref)
+     if (pyobj->IsSmart() && Cppyy::IsSubtype(oisa, fUnderlyingType)) {
+-- 
+2.44.0
+

bindings/pyroot/cppyy/sync-upstream

@@ -49,6 +49,7 @@ git apply patches/CPyCppyy-Add-converters-and-executors-for-ROOT-types.patch
 git apply patches/CPyCppyy-TString_converter.patch
 git apply patches/CPyCppyy-Adapt-to-no-std-in-ROOT.patch
 git apply patches/CPyCppyy-Always-convert-returned-std-string.patch
+git apply patches/CPyCppyy-Disable-implicit-conversion-to-smart-ptr.patch
 git apply patches/cppyy-No-CppyyLegacy-namespace.patch
 git apply patches/cppyy-Remove-Windows-workaround.patch
 git apply patches/cppyy-Don-t-enable-cling-autoloading.patch