Dear Jason, dear all,
Jason Merrill wrote on 5 Dec 2018:
> You can get at the destructor with CLASSTYPE_DESTRUCTOR rather than walking
> through TYPE_FIELDS. I'd also check DECL_DEFAULTED_IN_CLASS_P.
> I'd also do this in maybe_emit_vtables rather than here, so that it only
> happens once per class.
Updated patch. I also added a test case which checks that the destructor
is not generated.
[ Original patch: https://gcc.gnu.org/ml/gcc-patches/2018-11/msg01824.html ]
Background again:
If a class contains any 'virtual ... = 0', it's an abstract class and for an
abstract class, the destructor not added to the vtable.
For a normal
virtual ~class() { }
that's not a problem as the class::~class() destructor will be generated
during
the parsing of the function.
But for
virtual ~class() = default;
the destructor will be generated via mark_used via the vtable.
If one now declares a derived class and uses it, the class::~class() is
generated
in that translation unit. Unless, #pragma interface/implementation is used.
In that case, the 'default' destructor will never be generated.
Build and regtested on x86_64-gnu-linux.
OK? Or do you have more suggested changes?
Tobias
2019-01-11 Tobias Burnus <bur...@net-b.de>
PR C++/88114
* decl2.c (maybe_emit_vtables): If needed, generate code for
the destructor of an abstract class.
(mark_used): Update comment for older function-name change.
PR C++/88114
* g++.dg/cpp0x/defaulted61.C: New.
* g++.dg/cpp0x/defaulted62.C: New.
diff --git a/gcc/cp/decl2.c b/gcc/cp/decl2.c
index dbab95fbc96..2e7ecdaa01c 100644
--- a/gcc/cp/decl2.c
+++ b/gcc/cp/decl2.c
@@ -2220,6 +2220,17 @@ maybe_emit_vtables (tree ctype)
}
}
+ /* For abstract classes, the destructor has been removed from the
+ vtable (in class.c's build_vtbl_initializer). For a compiler-
+ generated destructor, it hence might not have been generated in
+ this translation unit - and with '#pragma interface' it might
+ never get generated. */
+ if (CLASSTYPE_PURE_VIRTUALS (ctype)
+ && TYPE_HAS_NONTRIVIAL_DESTRUCTOR (ctype)
+ && DECL_DEFAULTED_IN_CLASS_P(CLASSTYPE_DESTRUCTOR(ctype))
+ && DECL_DEFAULTED_FN (CLASSTYPE_DESTRUCTOR(ctype)))
+ note_vague_linkage_fn (CLASSTYPE_DESTRUCTOR(ctype));
+
/* Since we're writing out the vtable here, also write the debug
info. */
note_debug_info_needed (ctype);
@@ -5497,7 +5508,7 @@ mark_used (tree decl, tsubst_flags_t complain)
within the body of a function so as to avoid collecting live data
on the stack (such as overload resolution candidates).
- We could just let cp_write_global_declarations handle synthesizing
+ We could just let c_parse_final_cleanups handle synthesizing
this function by adding it to deferred_fns, but doing
it at the use site produces better error messages. */
++function_depth;
diff --git a/gcc/testsuite/g++.dg/cpp0x/defaulted61.C b/gcc/testsuite/g++.dg/cpp0x/defaulted61.C
new file mode 100644
index 00000000000..e7e0a486292
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/defaulted61.C
@@ -0,0 +1,22 @@
+// { dg-do compile { target c++11 } }
+// { dg-final { scan-assembler "_ZN3OneD0Ev" } }
+
+// PR C++/88114
+// Destructor of an abstract class was never generated
+// when compiling the class - nor later due to the
+// '#pragma interface'
+
+#pragma implementation
+#pragma interface
+
+class One
+{
+ public:
+ virtual ~One() = default;
+ void some_fn();
+ virtual void later() = 0;
+ private:
+ int m_int;
+};
+
+void One::some_fn() { }
diff --git a/gcc/testsuite/g++.dg/cpp0x/defaulted62.C b/gcc/testsuite/g++.dg/cpp0x/defaulted62.C
new file mode 100644
index 00000000000..d8dab608816
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/defaulted62.C
@@ -0,0 +1,25 @@
+// { dg-do compile { target c++11 } }
+// { dg-final { scan-assembler-not "_ZN3OneD0Ev" } }
+
+// PR C++/88114
+// Destructor of an abstract class was never generated
+// when compiling the class - nor later due to the
+// '#pragma interface'
+// -> g++.dg/cpp0x/defaulted61.C
+
+// HERE, in g++.dg/cpp0x/defaulted62.C:
+// As we have commented the pragmas, it should NOT be created
+// #pragma implementation
+// #pragma interface
+
+class One
+{
+ public:
+ virtual ~One() = default;
+ void some_fn();
+ virtual void later() = 0;
+ private:
+ int m_int;
+};
+
+void One::some_fn() { }
