Bootstrapped and regtested on x86_64-pc-linux-gnu with
GXX_TESTSUITE_STDS=98,11,14,17,20,23,26,impcx.
-- >8 --
This patch improves the errors given when casting from void* in C++26 to
include the expected type if the type of the pointed-to object was
not similar to the casted-to type.
It also ensures (for all standard modes) that void* casts are checked
even for DECL_ARTIFICIAL declarations, such as lifetime-extended
temporaries, and is only ignored for cases where we know it's OK (heap
identifiers and source_location::current). This provides more accurate
diagnostics when using the pointer and ensures that some other casts
from void* are now correctly rejected.
gcc/cp/ChangeLog:
* constexpr.cc (is_std_source_location_current): New.
(cxx_eval_constant_expression): Only ignore cast from void* for
specific cases and improve other diagnostics.
gcc/testsuite/ChangeLog:
* g++.dg/cpp0x/constexpr-cast4.C: New test.
Signed-off-by: Nathaniel Shead <nathanielosh...@gmail.com>
---
gcc/cp/constexpr.cc | 83 +++++++++++++++++---
gcc/testsuite/g++.dg/cpp0x/constexpr-cast4.C | 7 ++
2 files changed, 78 insertions(+), 12 deletions(-)
create mode 100644 gcc/testsuite/g++.dg/cpp0x/constexpr-cast4.C
diff --git a/gcc/cp/constexpr.cc b/gcc/cp/constexpr.cc
index 0f948db7c2d..f38d541a662 100644
--- a/gcc/cp/constexpr.cc
+++ b/gcc/cp/constexpr.cc
@@ -2301,6 +2301,36 @@ is_std_allocator_allocate (const constexpr_call *call)
&& is_std_allocator_allocate (call->fundef->decl));
}
+/* Return true if FNDECL is std::source_location::current. */
+
+static inline bool
+is_std_source_location_current (tree fndecl)
+{
+ if (!decl_in_std_namespace_p (fndecl))
+ return false;
+
+ tree name = DECL_NAME (fndecl);
+ if (name == NULL_TREE || !id_equal (name, "current"))
+ return false;
+
+ tree ctx = DECL_CONTEXT (fndecl);
+ if (ctx == NULL_TREE || !CLASS_TYPE_P (ctx) || !TYPE_MAIN_DECL (ctx))
+ return false;
+
+ name = DECL_NAME (TYPE_MAIN_DECL (ctx));
+ return name && id_equal (name, "source_location");
+}
+
+/* Overload for the above taking constexpr_call*. */
+
+static inline bool
+is_std_source_location_current (const constexpr_call *call)
+{
+ return (call
+ && call->fundef
+ && is_std_source_location_current (call->fundef->decl));
+}
+
/* Return true if FNDECL is __dynamic_cast. */
static inline bool
@@ -7850,33 +7880,62 @@ cxx_eval_constant_expression (const constexpr_ctx *ctx,
tree t,
if (TYPE_PTROB_P (type)
&& TYPE_PTR_P (TREE_TYPE (op))
&& VOID_TYPE_P (TREE_TYPE (TREE_TYPE (op)))
- /* Inside a call to std::construct_at or to
- std::allocator<T>::{,de}allocate, we permit casting from void*
+ /* Inside a call to std::construct_at,
+ std::allocator<T>::{,de}allocate, or
+ std::source_location::current, we permit casting from void*
because that is compiler-generated code. */
&& !is_std_construct_at (ctx->call)
- && !is_std_allocator_allocate (ctx->call))
+ && !is_std_allocator_allocate (ctx->call)
+ && !is_std_source_location_current (ctx->call))
{
/* Likewise, don't error when casting from void* when OP is
&heap uninit and similar. */
tree sop = tree_strip_nop_conversions (op);
- if (TREE_CODE (sop) == ADDR_EXPR
- && VAR_P (TREE_OPERAND (sop, 0))
- && DECL_ARTIFICIAL (TREE_OPERAND (sop, 0)))
+ tree decl = NULL_TREE;
+ if (TREE_CODE (sop) == ADDR_EXPR)
+ decl = TREE_OPERAND (sop, 0);
+ if (decl
+ && VAR_P (decl)
+ && DECL_ARTIFICIAL (decl)
+ && (DECL_NAME (decl) == heap_identifier
+ || DECL_NAME (decl) == heap_uninit_identifier
+ || DECL_NAME (decl) == heap_vec_identifier
+ || DECL_NAME (decl) == heap_vec_uninit_identifier))
/* OK */;
/* P2738 (C++26): a conversion from a prvalue P of type "pointer to
cv void" to a pointer-to-object type T unless P points to an
object whose type is similar to T. */
- else if (cxx_dialect > cxx23
- && (sop = cxx_fold_indirect_ref (ctx, loc,
- TREE_TYPE (type), sop)))
+ else if (cxx_dialect > cxx23)
{
- r = build1 (ADDR_EXPR, type, sop);
- break;
+ r = cxx_fold_indirect_ref (ctx, loc, TREE_TYPE (type), sop);
+ if (r)
+ {
+ r = build1 (ADDR_EXPR, type, r);
+ break;
+ }
+ if (!ctx->quiet)
+ {
+ if (TREE_CODE (sop) == ADDR_EXPR)
+ {
+ error_at (loc, "cast from %qT is not allowed because "
+ "pointed-to type %qT is not similar to %qT",
+ TREE_TYPE (op), TREE_TYPE (TREE_TYPE (sop)),
+ TREE_TYPE (type));
+ tree obj = build_fold_indirect_ref (sop);
+ inform (DECL_SOURCE_LOCATION (obj),
+ "pointed-to object declared here");
+ }
+ else
+ error_at (loc, "cast from %qT is not allowed",
+ TREE_TYPE (op));
+ }
+ *non_constant_p = true;
+ return t;
}
else
{
if (!ctx->quiet)
- error_at (loc, "cast from %qT is not allowed",
+ error_at (loc, "cast from %qT is not allowed before C++26",
TREE_TYPE (op));
*non_constant_p = true;
return t;
diff --git a/gcc/testsuite/g++.dg/cpp0x/constexpr-cast4.C
b/gcc/testsuite/g++.dg/cpp0x/constexpr-cast4.C
new file mode 100644
index 00000000000..0e7fd87add8
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/constexpr-cast4.C
@@ -0,0 +1,7 @@
+// { dg-do compile { target c++11 } }
+
+constexpr int&& r = 1 + 2; // { dg-message "pointed-to object declared here"
"" { target c++26 } }
+constexpr void *vpr = &r;
+constexpr int* pi = static_cast<int *>(vpr); // { dg-error "cast from
.void\\*. is not allowed" "" { target c++23_down } }
+constexpr float* pf = static_cast<float *>(vpr); // { dg-error "cast from
.void\\*. is not allowed" "" { target c++23_down } }
+// { dg-error "cast from .void\\*. is not allowed because pointed-to type
.int. is not similar to .float." "" { target c++26 } .-1 }
--
2.42.0
