78 lines
2.2 KiB
Diff
78 lines
2.2 KiB
Diff
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commit 6d134ca4b963706f31251f061fc180e517b32546
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Author: Martin Sebor <msebor@redhat.com>
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Date: Tue Feb 23 14:09:00 2021 -0700
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PR c++/99074 - crash in dynamic_cast<>() on null pointer
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libstdc++-v3/ChangeLog:
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PR c++/99074
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* libsupc++/dyncast.cc (__dynamic_cast): Return null when
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first argument is null.
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gcc/testsuite/ChangeLog:
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PR c++/99074
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* g++.dg/warn/Wnonnull11.C: New test.
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diff --git a/gcc/testsuite/g++.dg/warn/Wnonnull11.C b/gcc/testsuite/g++.dg/warn/Wnonnull11.C
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new file mode 100644
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index 00000000000..5f1b69d9a41
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--- /dev/null
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+++ b/gcc/testsuite/g++.dg/warn/Wnonnull11.C
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@@ -0,0 +1,40 @@
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+/* PR c++/99074 - gcc 8 and above is crashing with dynamic_cast<>() on null
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+ pointer with optimization level -O1 and above
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+ { dg-do run }
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+ { dg-options "-O1 -Wall" } */
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+
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+class Base
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+{
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+public:
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+ virtual ~Base() {}
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+ virtual void op() = 0;
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+};
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+
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+class Object: public virtual Base { };
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+
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+class AbstractBase: public virtual Base
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+{
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+public:
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+ Object* _to_object ()
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+ {
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+ return dynamic_cast<Object*>(this); // { dg-warning "\\\[-Wnonnull" "" { xfail *-*-* } }
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+ }
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+};
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+
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+class MyAbstractClass: public virtual AbstractBase
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+{
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+public:
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+ static MyAbstractClass* _nil () { return 0; }
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+};
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+
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+
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+int main ()
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+{
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+ MyAbstractClass *my_abs_type = MyAbstractClass::_nil ();
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+ AbstractBase *abs_base = my_abs_type;
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+ Object *obj = abs_base->_to_object ();
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+
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+ __builtin_printf ("object is: %p\n", obj);
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+
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+ return 0;
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+}
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diff --git a/libstdc++-v3/libsupc++/dyncast.cc b/libstdc++-v3/libsupc++/dyncast.cc
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index b7d98495ad3..f8f707ee4d4 100644
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--- a/libstdc++-v3/libsupc++/dyncast.cc
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+++ b/libstdc++-v3/libsupc++/dyncast.cc
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@@ -47,6 +47,9 @@ __dynamic_cast (const void *src_ptr, // object started from
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const __class_type_info *dst_type, // desired target type
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ptrdiff_t src2dst) // how src and dst are related
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{
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+ if (!src_ptr)
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+ /* Handle precondition violations gracefully. */
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+ return NULL;
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const void *vtable = *static_cast <const void *const *> (src_ptr);
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const vtable_prefix *prefix =
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adjust_pointer <vtable_prefix> (vtable,
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