[PATCH] c++: ICE with -Wtautological-compare in template [PR116534]

[Marek Polacek]

Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk/14?

-- >8 --
Pre r14-4793, we'd call warn_tautological_cmp -> operand_equal_p
with operands wrapped in NON_DEPENDENT_EXPR, which works, since
o_e_p bails for codes it doesn't know.  But now we pass operands
not encapsulated in NON_DEPENDENT_EXPR, and crash, because the
template tree for &a[x] has null DECL_FIELD_OFFSET.

I don't think I meant this warning to be called in a template,
so let's avoid the problem this easy way.

        PR c++/116534

gcc/cp/ChangeLog:

        * call.cc (build_new_op) <case NE_EXPR>: Don't call
        warn_tautological_cmp in a template.

gcc/testsuite/ChangeLog:

        * g++.dg/warn/Wtautological-compare4.C: New test.
---
 gcc/cp/call.cc                                |  4 +++-
 .../g++.dg/warn/Wtautological-compare4.C      | 21 +++++++++++++++++++
 2 files changed, 24 insertions(+), 1 deletion(-)
 create mode 100644 gcc/testsuite/g++.dg/warn/Wtautological-compare4.C

diff --git a/gcc/cp/call.cc b/gcc/cp/call.cc
index fa7f05d76f6..d0d0c4b4d3c 100644
--- a/gcc/cp/call.cc
+++ b/gcc/cp/call.cc
@@ -7526,7 +7526,9 @@ build_new_op (const op_location_t &loc, enum tree_code 
code, int flags,
          && ((code_orig_arg1 == BOOLEAN_TYPE)
              ^ (code_orig_arg2 == BOOLEAN_TYPE)))
        maybe_warn_bool_compare (loc, code, arg1, arg2);
-      if (complain & tf_warning && warn_tautological_compare)
+      if ((complain & tf_warning)
+         && warn_tautological_compare
+         && !processing_template_decl)
        warn_tautological_cmp (loc, code, arg1, arg2);
       /* Fall through.  */
     case SPACESHIP_EXPR:
diff --git a/gcc/testsuite/g++.dg/warn/Wtautological-compare4.C 
b/gcc/testsuite/g++.dg/warn/Wtautological-compare4.C
new file mode 100644
index 00000000000..96308f49a42
--- /dev/null
+++ b/gcc/testsuite/g++.dg/warn/Wtautological-compare4.C
@@ -0,0 +1,21 @@
+// PR c++/116534
+// { dg-do compile }
+// { dg-options "-Wall" }
+
+template <class A>
+struct Test {
+    bool foo(unsigned x, unsigned y) {
+        bool test = &a[x] == &b[y];
+       return test;
+    }
+    unsigned *a;
+    unsigned *b;
+};
+
+void
+g ()
+{
+  Test<int> t;
+  t.foo (0u, 1u);
+  t.foo (0u, 0u);
+}

base-commit: cdd5dd2125ca850aa8599f76bed02509590541ef
-- 
2.46.0