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protect fresh proxy get() results in conversion and assignment operators #1492

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10 changes: 10 additions & 0 deletions ChangeLog
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Original file line number Diff line number Diff line change
@@ -1,3 +1,13 @@
2026-08-03 Kevin Ushey <kevinushey@gmail.com>

* inst/include/Rcpp/api/meat/proxy.h: Protect fresh SEXPs returned
from proxy get() in conversion and assignment operators (#1491)
* inst/include/Rcpp/proxy/Binding.h: Idem
* inst/include/Rcpp/proxy/NamesProxy.h: Idem
* inst/include/Rcpp/proxy/SlotProxy.h: Idem
* inst/tinytest/cpp/misc.cpp: Add regression tests
* inst/tinytest/test_misc.R: Idem

2026-07-24 Dirk Eddelbuettel <edd@debian.org>

* DESCRIPTION (Version, Date): Roll micro version and date
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44 changes: 30 additions & 14 deletions inst/include/Rcpp/api/meat/proxy.h
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Original file line number Diff line number Diff line change
Expand Up @@ -37,7 +37,8 @@ AttributeProxyPolicy<CLASS>::AttributeProxy::operator=(const T& rhs) {
template <typename CLASS>
template <typename T>
AttributeProxyPolicy<CLASS>::AttributeProxy::operator T() const {
return as<T>(get());
Shield<SEXP> x(get());
return as<T>(x);
}

template <typename CLASS>
Expand All @@ -48,7 +49,8 @@ AttributeProxyPolicy<CLASS>::AttributeProxy::operator SEXP() const {
template <typename CLASS>
template <typename T>
AttributeProxyPolicy<CLASS>::const_AttributeProxy::operator T() const {
return as<T>(get());
Shield<SEXP> x(get());
return as<T>(x);
}

template <typename CLASS>
Expand All @@ -68,13 +70,15 @@ NamesProxyPolicy<CLASS>::NamesProxy::operator=(const T& rhs) {
template <typename CLASS>
template <typename T>
NamesProxyPolicy<CLASS>::NamesProxy::operator T() const {
return as<T>( get() );
Shield<SEXP> x(get());
return as<T>(x);
}

template <typename CLASS>
template <typename T>
NamesProxyPolicy<CLASS>::const_NamesProxy::operator T() const {
return as<T>( get() );
Shield<SEXP> x(get());
return as<T>(x);
}

// SlotProxy
Expand All @@ -89,7 +93,8 @@ SlotProxyPolicy<CLASS>::SlotProxy::operator=(const T& rhs) {
template <typename CLASS>
template <typename T>
SlotProxyPolicy<CLASS>::SlotProxy::operator T() const {
return as<T>(get());
Shield<SEXP> x(get());
return as<T>(x);
}

// TagProxy
Expand All @@ -104,7 +109,8 @@ TagProxyPolicy<CLASS>::TagProxy::operator=(const T& rhs) {
template <typename CLASS>
template <typename T>
TagProxyPolicy<CLASS>::TagProxy::operator T() const {
return as<T>(get());
Shield<SEXP> x(get());
return as<T>(x);
}

template <typename CLASS>
Expand All @@ -115,7 +121,8 @@ TagProxyPolicy<CLASS>::TagProxy::operator SEXP() const {
template <typename CLASS>
template <typename T>
TagProxyPolicy<CLASS>::const_TagProxy::operator T() const {
return as<T>(get());
Shield<SEXP> x(get());
return as<T>(x);
}

template <typename CLASS>
Expand All @@ -135,13 +142,15 @@ BindingPolicy<CLASS>::Binding::operator=(const T& rhs) {
template <typename CLASS>
template <typename T>
BindingPolicy<CLASS>::Binding::operator T() const {
return as<T>(get());
Shield<SEXP> x(get());
return as<T>(x);
}

template <typename CLASS>
template <typename T>
BindingPolicy<CLASS>::const_Binding::operator T() const {
return as<T>(get());
Shield<SEXP> x(get());
return as<T>(x);
}

// DottedPairProxy
Expand All @@ -163,20 +172,25 @@ DottedPairProxyPolicy<CLASS>::DottedPairProxy::operator=(const traits::named_obj
template <typename CLASS>
template <typename T>
DottedPairProxyPolicy<CLASS>::DottedPairProxy::operator T() const {
return as<T>(get());
Shield<SEXP> x(get());
return as<T>(x);
}

template <typename CLASS>
template <typename T>
DottedPairProxyPolicy<CLASS>::const_DottedPairProxy::operator T() const {
return as<T>(get());
Shield<SEXP> x(get());
return as<T>(x);
}

// FieldProxy
template <typename CLASS>
typename FieldProxyPolicy<CLASS>::FieldProxy&
FieldProxyPolicy<CLASS>::FieldProxy::operator=(const FieldProxyPolicy<CLASS>::FieldProxy& rhs) {
if (this != &rhs) set(rhs.get());
if (this != &rhs) {
Shield<SEXP> x(rhs.get());
set(x);
}
return *this;
}

Expand All @@ -191,13 +205,15 @@ FieldProxyPolicy<CLASS>::FieldProxy::operator=(const T& rhs) {
template <typename CLASS>
template <typename T>
FieldProxyPolicy<CLASS>::FieldProxy::operator T() const {
return as<T>(get());
Shield<SEXP> x(get());
return as<T>(x);
}

template <typename CLASS>
template <typename T>
FieldProxyPolicy<CLASS>::const_FieldProxy::operator T() const {
return as<T>(get());
Shield<SEXP> x(get());
return as<T>(x);
}

}
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8 changes: 6 additions & 2 deletions inst/include/Rcpp/proxy/Binding.h
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Expand Up @@ -45,8 +45,12 @@ class BindingPolicy {
env.unlockBinding(name) ;
}
Binding& operator=(const Binding& rhs){
if( *this != rhs )
set( rhs.get() ) ;
// NB: '*this != rhs' previously used here would not compile
// when this operator was instantiated

@eddelbuettel eddelbuettel Aug 3, 2026

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Odd. Thanks for persisting here too.

if( env.get__() != rhs.env.get__() || name != rhs.name ) {
Shield<SEXP> x( rhs.get() ) ;
set(x) ;
}
return *this ;
}

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5 changes: 4 additions & 1 deletion inst/include/Rcpp/proxy/NamesProxy.h
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Expand Up @@ -31,7 +31,10 @@ class NamesProxyPolicy{

/* lvalue uses */
NamesProxy& operator=(const NamesProxy& rhs) {
if( this != &rhs) set( rhs.get() ) ;
if( this != &rhs) {
Shield<SEXP> x( rhs.get() ) ;
set(x) ;
}
return *this ;
}

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6 changes: 4 additions & 2 deletions inst/include/Rcpp/proxy/SlotProxy.h
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Expand Up @@ -33,7 +33,8 @@ class SlotProxyPolicy {
}

SlotProxy& operator=(const SlotProxy& rhs){
set( rhs.get() ) ;
Shield<SEXP> x( rhs.get() ) ;
set(x) ;
return *this ;
}

Expand Down Expand Up @@ -65,7 +66,8 @@ class SlotProxyPolicy {
}

template <typename T> operator T() const {
return as<T>( get() );
Shield<SEXP> x( get() );
return as<T>(x);
}
inline operator SEXP() const {
return get() ;
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10 changes: 10 additions & 0 deletions inst/tinytest/cpp/misc.cpp
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Expand Up @@ -173,6 +173,16 @@ StretchyList named_stretchy_list() {
return out;
}

// [[Rcpp::export]]
void copy_field_gc(Reference a, Reference b) {
a.field("x") = b.field("y");
}

// [[Rcpp::export]]
void copy_binding_gc(Environment a, Environment b) {
a["x"] = b["y"];
}

// [[Rcpp::export]]
void test_stop_variadic() {
stop( "%s %d", "foo", 3 );
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28 changes: 28 additions & 0 deletions inst/tinytest/test_misc.R
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Expand Up @@ -129,6 +129,34 @@ expect_equal(stretchy_list(), pairlist( "foo", 1L, 3.2 ))
# test.named_StretchyList <- function(){
expect_equal(named_stretchy_list(), pairlist( a = "foo", b = 1L, c = 3.2 ))

# test.FieldProxy.gc <- function(){
## copying a field whose value is computed freshly on access must keep
## that value protected across the assignment (#1491)
FooGC <- setRefClass("FooGC", fields = list(
x = "ANY",
y = function(value) {
if (missing(value)) new.env(parent = emptyenv()) else stop("read-only")
}
))
a <- FooGC$new(x = NULL)
b <- FooGC$new(x = NULL)
gctorture(TRUE)
for (i in 1:20)
copy_field_gc(a, b)
gctorture(FALSE)
expect_true(is.environment(a$x))

# test.Binding.gc <- function(){
## same for environment-to-environment binding copies (#1491)
ea <- new.env()
eb <- new.env()
makeActiveBinding("y", function() new.env(parent = emptyenv()), eb)
gctorture(TRUE)
for (i in 1:20)
copy_binding_gc(ea, eb)
gctorture(FALSE)
expect_true(is.environment(ea$x))

# test.stop.variadic <- function(){
m <- tryCatch( test_stop_variadic(), error = function(e){
conditionMessage(e)
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