c-common.c (combine_strings): Also set TREE_READONLY.

	* c-common.c (combine_strings): Also set TREE_READONLY.
	Change warn_write_strings to flag_const_strings.
	* c-decl.c, c-tree.h: Likewise.
cp/
	* tree.c (lvalue_type): Fix for arrays.
	* typeck.c (string_conv_p): New fn.
	(convert_for_assignment): Use it.
	(build_unary_op): Use lvalue_type.
	* call.c (standard_conversion, convert_like): Use string_conv_p.
	(add_function_candidate): Use lvalue_type.
	* cvt.c (convert_to_reference): Likewise.
	* decl2.c (lang_decode_option): Ignore -traditional.
	* decl.c (init_decl_processing): flag_writable_strings inhibits
	flag_const_strings.
	* lang-options.h (lang_options): Add fconst-strings to the list
	of valid options.
	* decl2.c (lang_f_options, lang_decode_option): Likewise.

From-SVN: r21928

7 files changed, 88 insertions, 7 deletions

diff --git a/gcc/cp/ChangeLog b/gcc/cp/ChangeLog
index 1941f15..19db217 100644
--- a/gcc/cp/ChangeLog
+++ b/gcc/cp/ChangeLog
@@ -1,3 +1,22 @@
+1998-08-24  Jason Merrill  <jason@yorick.cygnus.com>
+
+	* tree.c (lvalue_type): Fix for arrays.
+	* typeck.c (string_conv_p): New fn.
+	(convert_for_assignment): Use it.
+	(build_unary_op): Use lvalue_type.
+	* call.c (standard_conversion, convert_like): Use string_conv_p.
+	(add_function_candidate): Use lvalue_type.
+	* cvt.c (convert_to_reference): Likewise.
+	* decl2.c (lang_decode_option): Ignore -traditional.
+	* decl.c (init_decl_processing): flag_writable_strings inhibits
+	flag_const_strings.
+
+1998-08-24  Andrew MacLeod  <amacleod@cygnus.com>
+
+	* lang-options.h (lang_options): Add fconst-strings to the list
+	of valid options.
+	* decl2.c (lang_f_options, lang_decode_option): Likewise.
+
 1998-08-24  Nathan Sidwell  <nathan@acm.org>
 
         * lex.c (real_yylex): Don't warn about long long constants if
diff --git a/gcc/cp/call.c b/gcc/cp/call.c
index 3eb0817..7c1e683 100644
--- a/gcc/cp/call.c
+++ b/gcc/cp/call.c
@@ -883,6 +883,9 @@ standard_conversion (to, from, expr)
 	/* OK */;
       else if (comp_ptr_ttypes (TREE_TYPE (to), TREE_TYPE (from)))
 	conv = build_conv (QUAL_CONV, to, conv);
+      else if (expr && string_conv_p (to, expr, 0))
+	/* converting from string constant to char *.  */
+	conv = build_conv (QUAL_CONV, to, conv);
       else if (ptr_reasonably_similar (TREE_TYPE (to), TREE_TYPE (from)))
 	{
 	  conv = build_conv (PTR_CONV, to, conv);
@@ -3172,6 +3175,11 @@ convert_like (convs, expr)
     case LVALUE_CONV:
       return decay_conversion (expr);
 
+    case QUAL_CONV:
+      /* Warn about deprecated conversion if appropriate.  */
+      string_conv_p (TREE_TYPE (convs), expr, 1);
+      break;
+      
     default:
       break;
     }
diff --git a/gcc/cp/cp-tree.h b/gcc/cp/cp-tree.h
index 82dc430b..26e39a9 100644
--- a/gcc/cp/cp-tree.h
+++ b/gcc/cp/cp-tree.h
@@ -342,9 +342,13 @@ extern int warn_ctor_dtor_privacy;
 
 extern int warn_return_type;
 
-/* Nonzero means give string constants the type `const char *'
-   to get extra warnings from them.  These warnings will be too numerous
-   to be useful, except in thoroughly ANSIfied programs.  */
+/* Nonzero means give string constants the type `const char *', as mandated
+   by the standard.  */
+
+extern int flag_const_strings;
+
+/* Nonzero means warn about deprecated conversion from string constant to
+   `char *'.  */
 
 extern int warn_write_strings;
 
diff --git a/gcc/cp/decl.c b/gcc/cp/decl.c
index 4942b5d..8c3a32b 100644
--- a/gcc/cp/decl.c
+++ b/gcc/cp/decl.c
@@ -6200,6 +6200,11 @@ init_decl_processing ()
 
   print_error_function = lang_print_error_function;
   lang_get_alias_set = &c_get_alias_set;
+
+  /* Maintain consistency.  Perhaps we should just complain if they
+     say -fwritable-strings?  */
+  if (flag_writable_strings)
+    flag_const_strings = 0;
 }
 
 /* Function to print any language-specific context for an error message.  */
diff --git a/gcc/cp/decl2.c b/gcc/cp/decl2.c
index 8d923be..9333d8d 100644
--- a/gcc/cp/decl2.c
+++ b/gcc/cp/decl2.c
@@ -211,9 +211,13 @@ int flag_use_repository;
 
 int flag_optional_diags = 1;
 
-/* Nonzero means give string constants the type `const char *'
-   to get extra warnings from them.  These warnings will be too numerous
-   to be useful, except in thoroughly ANSIfied programs.  */
+/* Nonzero means give string constants the type `const char *', as mandated
+   by the standard.  */
+
+int flag_const_strings = 1;
+
+/* Nonzero means warn about deprecated conversion from string constant to
+   `char *'.  */
 
 int warn_write_strings;
 
@@ -482,6 +486,7 @@ static struct { char *string; int *variable; int on_value;} lang_f_options[] =
   {"builtin", &flag_no_builtin, 0},
   {"ident", &flag_no_ident, 0},
   {"labels-ok", &flag_labels_ok, 1},
+  {"const-strings", &flag_const_strings, 1},
   {"stats", &flag_detailed_statistics, 1},
   {"this-is-variable", &flag_this_is_variable, 1},
   {"strict-prototype", &flag_strict_prototype, 1},
diff --git a/gcc/cp/lang-options.h b/gcc/cp/lang-options.h
index dc39d28..3c2aee9 100644
--- a/gcc/cp/lang-options.h
+++ b/gcc/cp/lang-options.h
@@ -38,6 +38,8 @@ DEFINE_LANG_NAME ("C++")
   { "-fno-check-new", "" },
   { "-fconserve-space", "Reduce size of object files" },
   { "-fno-conserve-space", "" },
+  { "-fconst-strings", "" },
+  { "-fno-const-strings", "Make string literals `char[]' instead of `const char[]'" },
   { "-fdefault-inline", "" },
   { "-fno-default-inline", "Do not inline mmeber functions be default"},
   { "-frtti", "" },
diff --git a/gcc/cp/typeck.c b/gcc/cp/typeck.c
index 3f79953..61ebe18 100644
--- a/gcc/cp/typeck.c
+++ b/gcc/cp/typeck.c
@@ -1757,6 +1757,42 @@ inline_conversion (exp)
     }
   return exp;
 }
+
+/* Returns nonzero iff exp is a STRING_CST or the result of applying
+   decay_conversion to one.  */
+
+int
+string_conv_p (totype, exp, warn)
+     tree totype, exp;
+     int warn;
+{
+  tree t;
+
+  if (! flag_const_strings || TREE_CODE (totype) != POINTER_TYPE)
+    return 0;
+
+  t = TREE_TYPE (totype);
+  if (! comptypes (t, char_type_node, 1)
+      && ! comptypes (t, wchar_type_node, 1))
+    return 0;
+
+  if (TREE_CODE (exp) != STRING_CST)
+    {
+      t = build_pointer_type (build_type_variant (t, 1, 0));
+      if (! comptypes (TREE_TYPE (exp), t, 1))
+	return 0;
+      STRIP_NOPS (exp);
+      if (TREE_CODE (exp) != ADDR_EXPR
+	  || TREE_CODE (TREE_OPERAND (exp, 0)) != STRING_CST)
+	return 0;
+    }
+
+  /* This warning is not very useful, as it complains about printf.  */
+  if (warn && warn_write_strings)
+    cp_warning ("deprecated conversion from string constant to `char *'");
+
+  return 1;
+}
 
 tree
 build_object_ref (datum, basetype, field)
@@ -6799,7 +6835,9 @@ convert_for_assignment (type, rhs, errtype, fndecl, parmnum)
 		}
 	      else if (! TYPE_READONLY (ttl) && TYPE_READONLY (ttr))
 		{
-		  if (fndecl)
+		  if (string_conv_p (type, rhs, 1))
+		    /* converting from string constant to char *, OK.  */;
+		  else if (fndecl)
 		    cp_pedwarn ("passing `%T' as argument %P of `%D' discards const",
 				rhstype, parmnum, fndecl);
 		  else