[rfc] Be in language c more c++ compatible

[Jan Kratochvil <jan dot kratochvil at redhat dot com>]

Hi,

I always see some terrible C++ GDB bug so I fix in some hours and then find out
it works in GDB when one has `set language c++'.  This usually happens with
artificial testcases like the one today:
	http://sourceware.org/ml/gdb-patches/2011-07/msg00387.html

I was told by Keith it also happens to him.

echo 'class C { typedef int t; t i; } c;'|g++ -c -o 1.o -g -x c++ -

FSF GDB HEAD
(gdb) show language 
The current source language is "auto; currently c".
(gdb) whatis C::t
type = C::t
(gdb) set language c++
(gdb) whatis C::t
type = int

patched FSF GDB HEAD:
(gdb) show language
The current source language is "auto; currently c".
(gdb) whatis C::t
type = int
(gdb) set language c++
(gdb) whatis C::t
type = int

The patch has two parts (two files), each part is sufficient to fix the problem
above.

The first (c-exp.y) part parses those parts of `language c++' which cannot
(I believe - RFC) lead to misinterpretation of any valid C code even in
`language c'.

The second (valops.c) part is there because with `language c++' parsing "C::t"
is straight OP_TYPE handled correctly in evaluate_subexp_standard.  But with
`language c' it gets parsed as OP_SCOPE and I find there a bug, copied the code
there.

Sure this patch is not a complete implementation of the idea, just an
incremental improvement.

No regressions on {x86_64,x86_64-m32,i686}-fedora15-linux-gnu.


Thanks,
Jan


gdb/
2011-07-15  Jan Kratochvil  <jan.kratochvil@redhat.com>

	* c-exp.y (tokentab3, tokentab2): Remove the cxx_only field, comment it.
	(lex_one_token): No longer check them there.
	(yylex): Do not check for language_cplus.
	* valops.c (value_maybe_namespace_elt): Dereference LOC_TYPEDEF for
	EVAL_AVOID_SIDE_EFFECTS.

--- a/gdb/c-exp.y
+++ b/gdb/c-exp.y
@@ -1867,38 +1867,40 @@ struct token
   int cxx_only;
 };
 
+/* cxx_only is not used.  */
 static const struct token tokentab3[] =
   {
-    {">>=", ASSIGN_MODIFY, BINOP_RSH, 0},
-    {"<<=", ASSIGN_MODIFY, BINOP_LSH, 0},
-    {"->*", ARROW_STAR, BINOP_END, 1}
+    {">>=", ASSIGN_MODIFY, BINOP_RSH},
+    {"<<=", ASSIGN_MODIFY, BINOP_LSH},
+    {"->*", ARROW_STAR, BINOP_END}
   };
 
+/* cxx_only is not used.  */
 static const struct token tokentab2[] =
   {
-    {"+=", ASSIGN_MODIFY, BINOP_ADD, 0},
-    {"-=", ASSIGN_MODIFY, BINOP_SUB, 0},
-    {"*=", ASSIGN_MODIFY, BINOP_MUL, 0},
-    {"/=", ASSIGN_MODIFY, BINOP_DIV, 0},
-    {"%=", ASSIGN_MODIFY, BINOP_REM, 0},
-    {"|=", ASSIGN_MODIFY, BINOP_BITWISE_IOR, 0},
-    {"&=", ASSIGN_MODIFY, BINOP_BITWISE_AND, 0},
-    {"^=", ASSIGN_MODIFY, BINOP_BITWISE_XOR, 0},
-    {"++", INCREMENT, BINOP_END, 0},
-    {"--", DECREMENT, BINOP_END, 0},
-    {"->", ARROW, BINOP_END, 0},
-    {"&&", ANDAND, BINOP_END, 0},
-    {"||", OROR, BINOP_END, 0},
+    {"+=", ASSIGN_MODIFY, BINOP_ADD},
+    {"-=", ASSIGN_MODIFY, BINOP_SUB},
+    {"*=", ASSIGN_MODIFY, BINOP_MUL},
+    {"/=", ASSIGN_MODIFY, BINOP_DIV},
+    {"%=", ASSIGN_MODIFY, BINOP_REM},
+    {"|=", ASSIGN_MODIFY, BINOP_BITWISE_IOR},
+    {"&=", ASSIGN_MODIFY, BINOP_BITWISE_AND},
+    {"^=", ASSIGN_MODIFY, BINOP_BITWISE_XOR},
+    {"++", INCREMENT, BINOP_END},
+    {"--", DECREMENT, BINOP_END},
+    {"->", ARROW, BINOP_END},
+    {"&&", ANDAND, BINOP_END},
+    {"||", OROR, BINOP_END},
     /* "::" is *not* only C++: gdb overrides its meaning in several
        different ways, e.g., 'filename'::func, function::variable.  */
-    {"::", COLONCOLON, BINOP_END, 0},
-    {"<<", LSH, BINOP_END, 0},
-    {">>", RSH, BINOP_END, 0},
-    {"==", EQUAL, BINOP_END, 0},
-    {"!=", NOTEQUAL, BINOP_END, 0},
-    {"<=", LEQ, BINOP_END, 0},
-    {">=", GEQ, BINOP_END, 0},
-    {".*", DOT_STAR, BINOP_END, 1}
+    {"::", COLONCOLON, BINOP_END},
+    {"<<", LSH, BINOP_END},
+    {">>", RSH, BINOP_END},
+    {"==", EQUAL, BINOP_END},
+    {"!=", NOTEQUAL, BINOP_END},
+    {"<=", LEQ, BINOP_END},
+    {">=", GEQ, BINOP_END},
+    {".*", DOT_STAR, BINOP_END}
   };
 
 /* Identifier-like tokens.  */
@@ -2075,10 +2077,6 @@ lex_one_token (void)
   for (i = 0; i < sizeof tokentab3 / sizeof tokentab3[0]; i++)
     if (strncmp (tokstart, tokentab3[i].operator, 3) == 0)
       {
-	if (tokentab3[i].cxx_only
-	    && parse_language->la_language != language_cplus)
-	  break;
-
 	lexptr += 3;
 	yylval.opcode = tokentab3[i].opcode;
 	return tokentab3[i].token;
@@ -2088,10 +2086,6 @@ lex_one_token (void)
   for (i = 0; i < sizeof tokentab2 / sizeof tokentab2[0]; i++)
     if (strncmp (tokstart, tokentab2[i].operator, 2) == 0)
       {
-	if (tokentab2[i].cxx_only
-	    && parse_language->la_language != language_cplus)
-	  break;
-
 	lexptr += 2;
 	yylval.opcode = tokentab2[i].opcode;
 	if (in_parse_field && tokentab2[i].token == ARROW)
@@ -2525,8 +2519,7 @@ yylex (void)
   current.token = lex_one_token ();
   if (current.token == NAME)
     current.token = classify_name (expression_context_block);
-  if (parse_language->la_language != language_cplus
-      || (current.token != TYPENAME && current.token != COLONCOLON))
+  if (current.token != TYPENAME && current.token != COLONCOLON)
     return current.token;
 
   first_was_coloncolon = current.token == COLONCOLON;
--- a/gdb/valops.c
+++ b/gdb/valops.c
@@ -3501,7 +3501,16 @@ value_maybe_namespace_elt (const struct type *curtype,
     return NULL;
   else if ((noside == EVAL_AVOID_SIDE_EFFECTS)
 	   && (SYMBOL_CLASS (sym) == LOC_TYPEDEF))
-    result = allocate_value (SYMBOL_TYPE (sym));
+    {
+      struct type *type = SYMBOL_TYPE (sym);
+
+      /* If this is a typedef, then find its immediate target.  We use
+	 check_typedef to resolve stubs, but we ignore its result because we do
+	 not want to dig past all typedefs.  */
+      check_typedef (type);
+      type = TYPE_TARGET_TYPE (type);
+      return allocate_value (type);
+    }
   else
     result = value_of_variable (sym, get_selected_block (0));