PR c/88546 - Copy attribute unusable for weakrefs

gcc/c-family/ChangeLog:

	PR c/88546
	* c-attribs.c (handle_copy_attribute): Avoid copying attribute leaf.
	Handle C++ empty throw specification and C11 _Noreturn.
	(has_attribute): Also handle C11 _Noreturn.

gcc/ChangeLog:

	PR c/88546
	* attribs.c (decls_mismatched_attributes): Avoid warning for attribute
	leaf.

gcc/testsuite/ChangeLog:

	PR c/88546
	* g++.dg/ext/attr-copy.C: New test.
	* gcc.dg/attr-copy-4.c: Disable macro expansion tracking.
	* gcc.dg/attr-copy-6.c: New test.
	* gcc.dg/attr-copy-7.c: New test.

From-SVN: r267591

gcc/ChangeLog

@@ -4,6 +4,12 @@
 
 2019-01-04  Martin Sebor  <msebor@redhat.com>
 
+	PR c/88546
+	* attribs.c (decls_mismatched_attributes): Avoid warning for attribute
+	leaf.
+
+2019-01-04  Martin Sebor  <msebor@redhat.com>
+
 	PR c/88363
 	* doc/extend.texi (attribute alloc_align, alloc_size): Update.
 

gcc/attribs.c

@@ -1912,6 +1912,12 @@ decls_mismatched_attributes (tree tmpl, tree decl, tree attrlist,
 
   for (unsigned i = 0; blacklist[i]; ++i)
     {
+      /* Attribute leaf only applies to extern functions.  Avoid mentioning
+	 it when it's missing from a static declaration.  */
+      if (!TREE_PUBLIC (decl)
+	  && !strcmp ("leaf", blacklist[i]))
+	continue;
+
       for (unsigned j = 0; j != 2; ++j)
 	{
 	  if (!has_attribute (tmpls[j], tmpl_attrs[j], blacklist[i]))

gcc/c-family/ChangeLog

 2019-01-04  Martin Sebor  <msebor@redhat.com>
 
+	PR c/88546
+	* c-attribs.c (handle_copy_attribute): Avoid copying attribute leaf.
+	Handle C++ empty throw specification and C11 _Noreturn.
+	(has_attribute): Also handle C11 _Noreturn.
+
+2019-01-04  Martin Sebor  <msebor@redhat.com>
+
 	PR c/88363
 	* c-attribs.c (positional_argument): Also accept enumerated types.
 

gcc/c-family/c-attribs.c

@@ -2461,6 +2461,12 @@ handle_copy_attribute (tree *node, tree name, tree args,
 	      || is_attribute_p ("weakref", atname))
 	    continue;
 
+	  /* Attribute leaf only applies to extern functions.
+	     Avoid copying it to static ones.  */
+	  if (!TREE_PUBLIC (decl)
+	      && is_attribute_p ("leaf", atname))
+	    continue;
+
 	  tree atargs = TREE_VALUE (at);
 	  /* Create a copy of just the one attribute ar AT, including
 	     its argumentsm and add it to DECL.  */
@@ -2478,13 +2484,28 @@ handle_copy_attribute (tree *node, tree name, tree args,
       return NULL_TREE;
     }
 
+  /* A function declared with attribute nothrow has the attribute
+     attached to it, but a C++ throw() function does not.  */
+  if (TREE_NOTHROW (ref))
+    TREE_NOTHROW (decl) = true;
+
+  /* Similarly, a function declared with attribute noreturn has it
+     attached on to it, but a C11 _Noreturn function does not.  */
   tree reftype = ref;
+  if (DECL_P (ref)
+      && TREE_THIS_VOLATILE (ref)
+      && FUNC_OR_METHOD_TYPE_P (TREE_TYPE (reftype)))
+    TREE_THIS_VOLATILE (decl) = true;
+
   if (DECL_P (ref) || EXPR_P (ref))
     reftype = TREE_TYPE (ref);
 
   if (POINTER_TYPE_P (reftype))
     reftype = TREE_TYPE (reftype);
 
+  if (!TYPE_P (reftype))
+    return NULL_TREE;
+
   tree attrs = TYPE_ATTRIBUTES (reftype);
 
   /* Copy type attributes from REF to DECL.  */
@@ -4194,6 +4215,15 @@ has_attribute (location_t atloc, tree t, tree attr, tree (*convert)(tree))
 	      if (expr && DECL_P (expr))
 		found_match = TREE_READONLY (expr);
 	    }
+	  else if (!strcmp ("noreturn", namestr))
+	    {
+	      /* C11 _Noreturn sets the volatile bit without attaching
+		 an attribute to the decl.  */
+	      if (expr
+		  && DECL_P (expr)
+		  && FUNC_OR_METHOD_TYPE_P (TREE_TYPE (expr)))
+		found_match = TREE_THIS_VOLATILE (expr);
+	    }
 	  else if (!strcmp ("pure", namestr))
 	    {
 	      if (expr && DECL_P (expr))

gcc/testsuite/ChangeLog

 2019-01-04  Martin Sebor  <msebor@redhat.com>
 
+	PR c/88546
+	* g++.dg/ext/attr-copy.C: New test.
+	* gcc.dg/attr-copy-4.c: Disable macro expansion tracking.
+	* gcc.dg/attr-copy-6.c: New test.
+	* gcc.dg/attr-copy-7.c: New test.
+
+2019-01-04  Martin Sebor  <msebor@redhat.com>
+
 	PR c/88363
 	* c-c++-common/attributes-4.c: New test.
 

gcc/testsuite/g++.dg/ext/attr-copy.C

+/* PR middle-end/88546 - Copy attribute unusable for weakrefs
+   { dg-do compile }
+   { dg-options "-O1 -Wall -fdump-tree-optimized" }
+   { dg-require-weak "" } */
+
+#define ATTR(...)   __attribute__ ((__VA_ARGS__))
+#define ASRT(expr)   _Static_assert (expr, #expr)
+
+extern "C" {
+
+  ATTR (leaf, nothrow) int
+  fnothrow ()
+  {
+    return 0;
+  }
+
+  static __typeof__ (fnothrow)
+    ATTR (weakref ("fnothrow"), copy (fnothrow))
+    alias_fnothrow;
+
+
+  ATTR (leaf) int
+  fthrow_none () throw ()
+  {
+    return 0;
+  }
+
+  // Verify that no warning is issued for the alias having less
+  // restrictive attributes than the target: nothrow.
+  static __typeof (fthrow_none)
+    ATTR (weakref ("fthrow_none"), copy (fthrow_none))
+    alias_fthrow_none;
+
+  // Same as above but with no definition of the target.
+  ATTR (leaf) int
+  fthrow_none_nodef () throw ();
+
+  static __typeof (fthrow_none_nodef)
+    ATTR (weakref ("fthrow_none_nodef"), copy (fthrow_none_nodef))
+    alias_fthrow_none_nodef;
+
+  // And again but without using typeof to make sure the nothrow
+  // bit is copied by attribute copy alone.
+  static int
+  ATTR (weakref ("fthrow_none_nodef"), copy (fthrow_none_nodef))
+    alias_fthrow_none_nodef_func ();
+}
+
+
+struct UsrClass
+{
+  ~UsrClass ();
+};
+
+// Verify that the nothrow attribute/bit was copied to the alias and
+// that no exception handling code is emitted in any of these calls.
+
+int call_alias_fnothrow ()
+{
+  UsrClass usr;
+  return alias_fnothrow ();
+}
+
+int call_alias_fthrow_none ()
+{
+  UsrClass usr;
+  return alias_fthrow_none ();
+}
+
+int call_alias_fthrow_none_nodef ()
+{
+  UsrClass usr;
+  return alias_fthrow_none_nodef ();
+}
+
+int call_alias_fthrow_none_nodef_func ()
+{
+  UsrClass usr;
+  return alias_fthrow_none_nodef_func ();
+}
+
+// { dg-final { scan-tree-dump-not "__builtin_unwind" "optimized" } }

gcc/testsuite/gcc.dg/attr-copy-4.c

 /* PR middle-end/81824 - Warn for missing attributes with function aliases
    Exercise attribute copy for types.
    { dg-do compile }
-   { dg-options "-O2 -Wall" } */
+   { dg-options "-O2 -Wall -ftrack-macro-expansion=0" } */
 
 #define Assert(expr)   typedef char AssertExpr[2 * !!(expr) - 1]
 

gcc/testsuite/gcc.dg/attr-copy-6.c

+/* PR middle-end/88546 - Copy attribute unusable for weakrefs
+   { dg-do compile }
+   { dg-options "-O2 -Wall" }
+   { dg-require-weak "" } */
+
+#define ATTR(...)   __attribute__ ((__VA_ARGS__))
+#define ASRT(expr)   _Static_assert (expr, #expr)
+
+/* Variable that is local to this translation unit but that can
+   be modified from other units by calling reset_unit_local().  */
+static int unit_local;
+
+void reset_unit_local (void)
+{
+  unit_local = 0;
+}
+
+/* Attribute leaf implies that fleaf() doesn't modify unit_local().  */
+ATTR (leaf, returns_nonnull)
+void* fleaf_retnz (void);
+
+/* Verify both attributes have been applied.  */
+ASRT (__builtin_has_attribute (fleaf_retnz, leaf));
+ASRT (__builtin_has_attribute (fleaf_retnz, returns_nonnull));
+
+/* Verify that attribute leaf has the expected effect.  */
+void call_fleaf_retnz (void)
+{
+  int i = unit_local;
+  void *p = fleaf_retnz ();
+
+  /* Expect both tests to be folded to false and the calls eliminated.  */
+  extern void call_fleaf_retnz_test_leaf_eliminated (void);
+  if (i != unit_local)
+    call_fleaf_retnz_test_leaf_eliminated ();
+
+  extern void call_fleaf_retnz_test_nonnull_eliminated (void);
+  if (p == 0)
+    call_fleaf_retnz_test_nonnull_eliminated ();
+}
+
+
+/* Verify that attribute copy copies the returns_nonnull attribute
+   but doesn't try to copy attribute leaf which only applies to extern
+   function.  */
+static ATTR (copy (fleaf_retnz), weakref ("fleaf_retnz"))
+void* fweakref_fleaf_retnz_copy (void);
+
+ASRT (!__builtin_has_attribute (fweakref_fleaf_retnz_copy, leaf));
+ASRT (__builtin_has_attribute (fweakref_fleaf_retnz_copy, returns_nonnull));
+
+void call_fweakref_fleaf_retnz_copy (void)
+{
+  int i = unit_local;
+  void *p = fweakref_fleaf_retnz_copy ();
+
+  /* Since leaf is not copied, expect the following test not to be
+     folded and the call to be emitted.  */
+  extern void call_fweakref_test_leaf_emitted (void);
+  if (i != unit_local)
+    call_fweakref_test_leaf_emitted ();
+
+  /* Expect the following test to be folded to false and the call
+     eliminated.  */
+  extern void call_fweakref_fleaf_nonnull_eliminated (void);
+  if (p == 0)
+    call_fweakref_fleaf_nonnull_eliminated ();
+}
+
+/* This is reduced from libgfortran/runtime/error.c.  Verify it
+   doesn't trigger warnings and that the noreturn bit is copied
+   to the alias by verifying that calling the alias in a non-void
+   function with no return statement isn't diagnosed.  */
+
+extern _Noreturn void fnoreturn (void);
+
+extern __typeof (fnoreturn)
+  ATTR (visibility ("hidden"))
+  fnoreturn __asm__ ("fnoreturn_name");
+
+void fnoreturn (void)
+{
+  __builtin_abort ();
+}
+
+extern __typeof (fnoreturn)
+  ATTR (alias ("fnoreturn_name"), copy (fnoreturn))
+  fnoreturn_alias;
+
+int call_fnoreturn_alias (void)
+{
+  fnoreturn_alias ();
+}

gcc/testsuite/gcc.dg/attr-copy-7.c

+/* PR middle-end/88546 - Copy attribute unusable for weakrefs
+   Verify that attribute noreturn (represented as volatile on function
+   decls) is interpreted correctly and doesn't affect variables.
+   { dg-do compile }
+   { dg-options "-O1 -Wall -fdump-tree-optimized" }*/
+
+#define ATTR(...)   __attribute__ ((__VA_ARGS__))
+#define ASRT(expr)   _Static_assert (expr, #expr)
+
+ATTR (noreturn) void fnoreturn (void);
+ATTR (copy (fnoreturn)) void fnoreturn_copy (void);
+ASRT (__builtin_has_attribute (fnoreturn_copy, noreturn));
+
+int call_fnoreturn_copy (void)
+{
+  fnoreturn_copy ();
+  fnoreturn_copy ();   // should be eliminated
+}
+
+// { dg-final { scan-tree-dump-times "fnoreturn_copy \\(\\);" 1 "optimized" } }
+
+
+_Noreturn void f_Noreturn (void);
+ATTR (copy (f_Noreturn)) void f_Noreturn_copy (void);
+ASRT (__builtin_has_attribute (f_Noreturn_copy, noreturn));
+
+int call_f_Noreturn_copy (void)
+{
+  f_Noreturn_copy ();
+  f_Noreturn_copy ();   // should be eliminated
+}
+
+// { dg-final { scan-tree-dump-times "f_Noreturn_copy \\(\\);" 1 "optimized" } }
+
+
+// Verify the combination of both is accepted and works too,
+// just for fun.
+ATTR (noreturn) _Noreturn void fnoreturn_Noreturn (void);
+ATTR (copy (fnoreturn_Noreturn)) void fnoreturn_Noreturn_copy (void);
+ASRT (__builtin_has_attribute (fnoreturn_Noreturn_copy, noreturn));
+
+int call_fnoreturn_Noreturn_copy (void)
+{
+  fnoreturn_Noreturn_copy ();
+  fnoreturn_Noreturn_copy ();   // should be eliminated
+}
+
+// { dg-final { scan-tree-dump-times "fnoreturn_Noreturn_copy \\(\\);" 1 "optimized" } }
+
+
+typedef void func_t (void);
+
+ATTR (noreturn) func_t func_noreturn;
+ATTR (copy (func_noreturn)) func_t func_noreturn_copy;
+ASRT (__builtin_has_attribute (func_noreturn_copy, noreturn));
+
+int call_func_noreturn_copy (void)
+{
+  func_noreturn_copy ();
+  func_noreturn_copy ();   // should be eliminated
+}
+
+// { dg-final { scan-tree-dump-times "func_noreturn_copy \\(\\);" 1 "optimized" } }
+
+
+// Finally, verify that the volatile bit isn't copied for variables.
+extern volatile int vi;
+
+int read_nonvolatile (void)
+{
+  ATTR (copy (vi)) int i = 0;
+
+  return i + i;   // should be folded to return 0;
+}
+
+// { dg-final { scan-tree-dump-times "return 0;" 1 "optimized" } }

libgcc/gthr-posix.h

@@ -87,7 +87,8 @@ typedef struct timespec __gthread_time_t;
 #  define __gthrw_pragma(pragma)
 # endif
 # define __gthrw2(name,name2,type) \
-  static __typeof(type) name __attribute__ ((__weakref__(#name2))); \
+  static __typeof(type) name \
+    __attribute__ ((__weakref__(#name2), __copy__ (type))); \
   __gthrw_pragma(weak type)
 # define __gthrw_(name) __gthrw_ ## name
 #else

libgfortran/libgfortran.h

@@ -202,7 +202,7 @@ extern int __mingw_snprintf (char *, size_t, const char *, ...)
 # define iexport(x)		iexport1(x, IPREFIX(x))
 # define iexport1(x,y)		iexport2(x,y)
 # define iexport2(x,y) \
-	extern __typeof(x) PREFIX(x) __attribute__((__alias__(#y)))
+  extern __typeof(x) PREFIX(x) __attribute__((__alias__(#y), __copy__ (x)))
 #else
 # define export_proto(x)	sym_rename(x, PREFIX(x))
 # define export_proto_np(x)	extern char swallow_semicolon