PR35503 - warn for restrict pointer

diff --git a/gcc/c-family/c-common.c b/gcc/c-family/c-common.c
index 3feb910..ec8778f 100644
--- a/gcc/c-family/c-common.c
+++ b/gcc/c-family/c-common.c
@@ -13057,4 +13057,27 @@  diagnose_mismatched_attributes (tree olddecl, tree newdecl)
   return warned;
 }
 
+/* Warn if an argument at position param_pos is passed to a
+   restrict-qualified param, and it aliases with another argument.  */
+
+void
+warn_for_restrict (location_t loc, unsigned param_pos, vec<tree, va_gc> *args)
+{
+  tree arg = (*args)[param_pos];
+  if (operand_equal_p (arg, null_pointer_node, 0))
+    return;
+
+  for (unsigned i = 0; i < args->length (); ++i)
+    {
+      if (i == param_pos)
+	continue;
+
+      tree current_arg = (*args)[i];
+      if (operand_equal_p (arg, current_arg, 0))
+	warning_at (loc, 0,
+		    "passing argument %u to restrict qualified parameter aliases with "
+		    "argument %u", param_pos + 1, i + 1);
+    }
+}
+
 #include "gt-c-family-c-common.h"
diff --git a/gcc/c-family/c-common.h b/gcc/c-family/c-common.h
index bc22baa..0526ad5 100644
--- a/gcc/c-family/c-common.h
+++ b/gcc/c-family/c-common.h
@@ -920,6 +920,7 @@  extern void c_parse_final_cleanups (void);
 
 extern void warn_for_omitted_condop (location_t, tree);
 extern void warn_for_memset (location_t, tree, tree, int);
+extern void warn_for_restrict (location_t, unsigned, vec<tree, va_gc> *);
 
 /* These macros provide convenient access to the various _STMT nodes.  */
 
diff --git a/gcc/c-family/c.opt b/gcc/c-family/c.opt
index a5358ed..a029a86 100644
--- a/gcc/c-family/c.opt
+++ b/gcc/c-family/c.opt
@@ -1012,6 +1012,11 @@  Wduplicate-decl-specifier
 C ObjC Var(warn_duplicate_decl_specifier) Warning LangEnabledBy(C ObjC,Wall)
 Warn when a declaration has duplicate const, volatile, restrict or _Atomic specifier.
 
+Wrestrict
+C C++ Var(warn_restrict) Warning LangEnabledBy(C C++,Wall)
+Warn when an argument passed to a restrict-qualified parameter aliases with
+another argument.
+
 ansi
 C ObjC C++ ObjC++
 A synonym for -std=c89 (for C) or -std=c++98 (for C++).
diff --git a/gcc/c/c-parser.c b/gcc/c/c-parser.c
index fe0c95f..54e1e87 100644
--- a/gcc/c/c-parser.c
+++ b/gcc/c/c-parser.c
@@ -8369,6 +8369,17 @@  c_parser_postfix_expression_after_primary (c_parser *parser,
 	      warn_for_memset (expr_loc, arg0, arg2, literal_zero_mask);
 	    }
 
+	  if (TREE_CODE (expr.value) == FUNCTION_DECL && warn_restrict)
+	    {
+	      unsigned param_pos = 0;
+	      for (tree t = TYPE_ARG_TYPES (TREE_TYPE (expr.value)); t; t = TREE_CHAIN (t), param_pos++) 
+		{
+		  tree type = TREE_VALUE (t);
+		  if (POINTER_TYPE_P (type) && TYPE_RESTRICT (type))
+		    warn_for_restrict (expr_loc, param_pos, exprlist);	
+		}
+	    }
+
 	  start = expr.get_start ();
 	  finish = parser->tokens_buf[0].get_finish ();
 	  expr.value
diff --git a/gcc/cp/parser.c b/gcc/cp/parser.c
index 690e928..4710a08 100644
--- a/gcc/cp/parser.c
+++ b/gcc/cp/parser.c
@@ -6878,6 +6878,20 @@  cp_parser_postfix_expression (cp_parser *parser, bool address_p, bool cast_p,
 		warn_for_memset (input_location, arg0, arg2, literal_mask);
 	      }
 
+	    if (TREE_CODE (postfix_expression) == FUNCTION_DECL
+		&& warn_restrict)
+	      {
+		unsigned param_pos = 0;
+		for (tree decl = DECL_ARGUMENTS (postfix_expression);
+		     decl != NULL_TREE;
+		     decl = DECL_CHAIN (decl), param_pos++)
+		  {
+		    tree type = TREE_TYPE (decl);
+		    if (POINTER_TYPE_P (type) && TYPE_RESTRICT (type))
+		      warn_for_restrict (input_location, param_pos, args);
+		  }	
+	      }	    
+
 	    if (TREE_CODE (postfix_expression) == COMPONENT_REF)
 	      {
 		tree instance = TREE_OPERAND (postfix_expression, 0);
diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
index 1f04501..ac8aab5 100644
--- a/gcc/doc/invoke.texi
+++ b/gcc/doc/invoke.texi
@@ -261,7 +261,7 @@  Objective-C and Objective-C++ Dialects}.
 -Wc++-compat -Wc++11-compat -Wc++14-compat -Wcast-align  -Wcast-qual  @gol
 -Wchar-subscripts -Wclobbered  -Wcomment -Wconditionally-supported  @gol
 -Wconversion -Wcoverage-mismatch -Wno-cpp -Wdangling-else -Wdate-time @gol
--Wdelete-incomplete @gol
+-Wdelete-incomplete -Wrestrict @gol
 -Wno-deprecated -Wno-deprecated-declarations -Wno-designated-init @gol
 -Wdisabled-optimization @gol
 -Wno-discarded-qualifiers -Wno-discarded-array-qualifiers @gol
@@ -5274,6 +5274,12 @@  compilations.
 Warn when deleting a pointer to incomplete type, which may cause
 undefined behavior at runtime.  This warning is enabled by default.
 
+@item -Wrestrict @r{(C and C++ only)}
+@opindex Wrestrict
+@opindex Wno-restrict
+Warn when an argument passed to a restrict-qualified parameter
+aliases with another argument
+
 @item -Wuseless-cast @r{(C++ and Objective-C++ only)}
 @opindex Wuseless-cast
 @opindex Wno-useless-cast
diff --git a/gcc/testsuite/c-c++-common/pr35503.c b/gcc/testsuite/c-c++-common/pr35503.c
new file mode 100644
index 0000000..fb12a71
--- /dev/null
+++ b/gcc/testsuite/c-c++-common/pr35503.c
@@ -0,0 +1,10 @@ 
+/* { dg-do compile } */
+/* { dg-options "-Wrestrict" } */
+
+int foo (const char *__restrict buf, const char *__restrict fmt, ...);
+
+void f(void)
+{
+  char buf[100] = "hello";
+  foo (buf, "%s-%s", buf, "world"); /*  { dg-warning "passing argument 1 to restrict qualified parameter aliases with argument 3" } */
+}