[C PATCH] Fix parsing when using declarations in for loops and typedefs (PR c/67784)

[Marek Polacek <polacek@redhat.com>]

As explained in the PR, the issue here was that we were treating a TYPENAME
wrongly as an ID.  That happened because we were using information from the
wrong scope when parsing a token after an else clause.  I.e. in fn1 in the
attached testcase we need to examine the token after "if (1);" to see if it's
the "else" keyword, but when it's not, we use the scope of the for loop when
classifying the token, so we wrongly see "T" as a identifier of a variable.
Fixed by examining the token again and reclassifying it.

Moreover, we were ICEing in a similar scenario, treating ID as a TYPENAME, as
demonstrated in pr67784-2.c.  The fix is analogical.

Bootstrapped/regtested on x86_64-linux, ok for trunk?

2015-11-12  Marek Polacek  <polacek@redhat.com>

	PR c/67784
	* c-parser.c (c_parser_for_statement): Reclassify the token in
	a correct scope.

	* gcc.dg/pr67784-1.c: New test.
	* gcc.dg/pr67784-2.c: New test.

diff --git gcc/c/c-parser.c gcc/c/c-parser.c
index 2484b92..8949825 100644
--- gcc/c/c-parser.c
+++ gcc/c/c-parser.c
@@ -5749,6 +5749,21 @@ c_parser_for_statement (c_parser *parser, bool ivdep)
     c_finish_loop (loc, cond, incr, body, c_break_label, c_cont_label, true);
   add_stmt (c_end_compound_stmt (loc, block, flag_isoc99 || c_dialect_objc ()));
 
+  /* We might need to reclassify any previously-lexed identifier, e.g.
+     when we've left a for loop with an if-statement without else in the
+     body - we might have used a wrong scope for the token.  See PR67784.  */
+  if (c_parser_next_token_is (parser, CPP_NAME))
+    {
+      c_token *token = c_parser_peek_token (parser);
+      tree decl = lookup_name (token->value);
+      if (decl == NULL_TREE)
+	;
+      else if (TREE_CODE (decl) == TYPE_DECL)
+	token->id_kind = C_ID_TYPENAME;
+      else if (VAR_P (decl))
+	token->id_kind = C_ID_ID;
+    }
+
   token_indent_info next_tinfo
     = get_token_indent_info (c_parser_peek_token (parser));
   warn_for_misleading_indentation (for_tinfo, body_tinfo, next_tinfo);
diff --git gcc/testsuite/gcc.dg/pr67784-1.c gcc/testsuite/gcc.dg/pr67784-1.c
index e69de29..d5e85fc 100644
--- gcc/testsuite/gcc.dg/pr67784-1.c
+++ gcc/testsuite/gcc.dg/pr67784-1.c
@@ -0,0 +1,54 @@
+/* PR c/67784 */
+/* { dg-do compile } */
+/* { dg-options "" } */
+
+typedef int T;
+
+void
+fn1 (void)
+{
+  for (int T;;)
+    if (1)
+      ;
+  T *x;
+}
+
+void
+fn2 (void)
+{
+  for (int T;;)
+    if (1)
+      T = 1;
+  T *x;
+}
+
+void
+fn3 (void)
+{
+  for (int T;;)
+    if (1)
+      {
+      }
+  T *x;
+}
+
+void
+fn4 (void)
+{
+  for (int T;;)
+    if (1)
+L:
+      ;
+  T *x;
+}
+
+void
+fn5 (void)
+{
+  for (int T;;)
+    if (1)
+      ;
+    else
+      ;
+  T *x;
+}
diff --git gcc/testsuite/gcc.dg/pr67784-2.c gcc/testsuite/gcc.dg/pr67784-2.c
index e69de29..de3b1c8 100644
--- gcc/testsuite/gcc.dg/pr67784-2.c
+++ gcc/testsuite/gcc.dg/pr67784-2.c
@@ -0,0 +1,54 @@
+/* PR c/67784 */
+/* { dg-do compile } */
+/* { dg-options "" } */
+
+int T;
+
+void
+fn1 (void)
+{
+  for (typedef int T;;) /* { dg-error "declaration of non-variable" } */
+    if (1)
+      ;
+  T *x; /* { dg-error "undeclared" } */
+}
+
+void
+fn2 (void)
+{
+  for (typedef int T;;) /* { dg-error "declaration of non-variable" } */
+    if (1)
+      T = 1; /* { dg-error "expected expression" } */
+  T *x; /* { dg-error "undeclared" } */
+}
+
+void
+fn3 (void)
+{
+  for (typedef int T;;) /* { dg-error "declaration of non-variable" } */
+    if (1)
+      {
+      }
+  T *x; /* { dg-error "undeclared" } */
+}
+
+void
+fn4 (void)
+{
+  for (typedef int T;;) /* { dg-error "declaration of non-variable" } */
+    if (1)
+L:
+      ;
+  T *x; /* { dg-error "undeclared" } */
+}
+
+void
+fn5 (void)
+{
+  for (typedef int T;;) /* { dg-error "declaration of non-variable" } */
+    if (1)
+      ;
+    else
+      ;
+  T *x; /* { dg-error "undeclared" } */
+}

	Marek