Re: [PATCH] c++: Fix -Wvexing-parse ICE with omitted int [PR97762]

[Jason Merrill via Gcc-patches]

On 11/9/20 11:47 AM, Marek Polacek wrote:

For declarations like

   long f();

decl_specifiers->type will be NULL, but I neglected to handle this case,
therefore we ICE.  So handle this case by pretending we've seen 'int',
which is good enough for -Wvexing-parse's purposes.

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

OK.

gcc/cp/ChangeLog:

        PR c++/97762
        * parser.c (warn_about_ambiguous_parse): Handle the case when
        there is no type in the decl-specifiers.

gcc/testsuite/ChangeLog:

        PR c++/97762
        * g++.dg/warn/Wvexing-parse8.C: New test.
---
  gcc/cp/parser.c                            | 23 ++++++++++++++++------
  gcc/testsuite/g++.dg/warn/Wvexing-parse8.C | 11 +++++++++++
  2 files changed, 28 insertions(+), 6 deletions(-)
  create mode 100644 gcc/testsuite/g++.dg/warn/Wvexing-parse8.C

diff --git a/gcc/cp/parser.c b/gcc/cp/parser.c
index bbf157eb47f..b14b4c90c92 100644
--- a/gcc/cp/parser.c
+++ b/gcc/cp/parser.c
@@ -20652,13 +20652,24 @@ warn_about_ambiguous_parse (const 
cp_decl_specifier_seq *decl_specifiers,
    if (declarator->parenthesized != UNKNOWN_LOCATION)
      return;

- tree type = decl_specifiers->type;

-  if (TREE_CODE (type) == TYPE_DECL)
-   type = TREE_TYPE (type);
+  tree type;
+  if (decl_specifiers->type)
+    {
+      type = decl_specifiers->type;
+      if (TREE_CODE (type) == TYPE_DECL)
+       type = TREE_TYPE (type);

- /* If the return type is void there is no ambiguity. */

-  if (same_type_p (type, void_type_node))
-    return;
+      /* If the return type is void there is no ambiguity.  */
+      if (same_type_p (type, void_type_node))
+       return;
+    }
+  else
+    {
+      /* Code like long f(); will have null ->type.  If we have any
+        type-specifiers, pretend we've seen int.  */
+      gcc_checking_assert (decl_specifiers->any_type_specifiers_p);
+      type = integer_type_node;
+    }

auto_diagnostic_group d;

    location_t loc = declarator->u.function.parens_loc;
diff --git a/gcc/testsuite/g++.dg/warn/Wvexing-parse8.C 
b/gcc/testsuite/g++.dg/warn/Wvexing-parse8.C
new file mode 100644
index 00000000000..2d26d22fc4b
--- /dev/null
+++ b/gcc/testsuite/g++.dg/warn/Wvexing-parse8.C
@@ -0,0 +1,11 @@
+// PR c++/97762
+// { dg-do compile }
+
+void
+g ()
+{
+  long a(); // { dg-warning "empty parentheses" }
+  signed b(); // { dg-warning "empty parentheses" }
+  unsigned c(); // { dg-warning "empty parentheses" }
+  short d(); // { dg-warning "empty parentheses" }
+}

base-commit: 4e85ad79a137535393d8dc169359e1730cab3533