8307147: [x86] Dangling pointer warning for Assembler::_attributes

Reviewed-by: dholmes, aph

src/hotspot/cpu/x86/assembler_x86.cpp

@@ -217,6 +217,17 @@ void Assembler::init_attributes(void) {
   _attributes = nullptr;
 }
 
+void Assembler::set_attributes(InstructionAttr* attributes) {
+  // Record the assembler in the attributes, so the attributes destructor can
+  // clear the assembler's attributes, cleaning up the otherwise dangling
+  // pointer.  gcc13 has a false positive warning, because it doesn't tie that
+  // cleanup to the assignment of _attributes here.
+  attributes->set_current_assembler(this);
+  PRAGMA_DIAG_PUSH
+  PRAGMA_DANGLING_POINTER_IGNORED
+  _attributes = attributes;
+  PRAGMA_DIAG_POP
+}
 
 void Assembler::membar(Membar_mask_bits order_constraint) {
   // We only have to handle StoreLoad
@@ -11442,7 +11453,6 @@ void Assembler::vex_prefix(Address adr, int nds_enc, int xreg_enc, VexSimdPrefix
     vex_x = adr.index_needs_rex();
   }
   set_attributes(attributes);
-  attributes->set_current_assembler(this);
 
   // For EVEX instruction (which is not marked as pure EVEX instruction) check and see if this instruction
   // is allowed in legacy mode and has resources which will fit in it.
@@ -11489,7 +11499,6 @@ int Assembler::vex_prefix_and_encode(int dst_enc, int nds_enc, int src_enc, VexS
   bool vex_b = (src_enc & 8) == 8;
   bool vex_x = false;
   set_attributes(attributes);
-  attributes->set_current_assembler(this);
 
   // For EVEX instruction (which is not marked as pure EVEX instruction) check and see if this instruction
   // is allowed in legacy mode and has resources which will fit in it.

src/hotspot/cpu/x86/assembler_x86.hpp

@@ -678,7 +678,8 @@ class Assembler : public AbstractAssembler  {
   bool _legacy_mode_vlbw;
   NOT_LP64(bool _is_managed;)
 
-  class InstructionAttr *_attributes;
+  InstructionAttr *_attributes;
+  void set_attributes(InstructionAttr* attributes);
 
   // 64bit prefixes
   void prefix(Register reg);
@@ -917,8 +918,6 @@ class Assembler : public AbstractAssembler  {
   // belong in macro assembler but there is no need for both varieties to exist
 
   void init_attributes(void);
-
-  void set_attributes(InstructionAttr *attributes) { _attributes = attributes; }
   void clear_attributes(void) { _attributes = nullptr; }
 
   void set_managed(void) { NOT_LP64(_is_managed = true;) }
@@ -2892,7 +2891,6 @@ class InstructionAttr {
     if (_current_assembler != nullptr) {
       _current_assembler->clear_attributes();
     }
-    _current_assembler = nullptr;
   }
 
 private:

src/hotspot/share/utilities/compilerWarnings.hpp

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2017, 2022, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2017, 2023, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -55,6 +55,10 @@
 #define ATTRIBUTE_SCANF(fmt, vargs)
 #endif
 
+#ifndef PRAGMA_DANGLING_POINTER_IGNORED
+#define PRAGMA_DANGLING_POINTER_IGNORED
+#endif
+
 #ifndef PRAGMA_FORMAT_NONLITERAL_IGNORED
 #define PRAGMA_FORMAT_NONLITERAL_IGNORED
 #endif

src/hotspot/share/utilities/compilerWarnings_gcc.hpp

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2017, 2022, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2017, 2023, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -39,6 +39,11 @@
 #define PRAGMA_DIAG_PUSH             _Pragma("GCC diagnostic push")
 #define PRAGMA_DIAG_POP              _Pragma("GCC diagnostic pop")
 
+// Disable -Wdangling-pointer which is introduced in GCC 12.
+#if !defined(__clang_major__) && (__GNUC__ >= 12)
+#define PRAGMA_DANGLING_POINTER_IGNORED PRAGMA_DISABLE_GCC_WARNING("-Wdangling-pointer")
+#endif
+
 #define PRAGMA_FORMAT_NONLITERAL_IGNORED                \
   PRAGMA_DISABLE_GCC_WARNING("-Wformat-nonliteral")     \
   PRAGMA_DISABLE_GCC_WARNING("-Wformat-security")