Re: [PATCH] c++: crash with requires-expr and -Wsequence-point [PR105304]

[Jason Merrill via Gcc-patches]

On 4/22/22 14:36, Patrick Palka wrote:

Here we're crashing from verify_sequence_points for this requires-expr
condition because it contains a templated CAST_EXPR with empty operand,
and verify_tree doesn't ignore this empty operand only because the
manual tail recursion that it perform for unary expression trees skips
the NULL test.

Bootstrapped and regtested on x86_64-pc-linux-gnu, does this look OK for
10/11/trunk?

OK.

        PR c++/105304

gcc/c-family/ChangeLog:

        * c-common.cc (verify_tree) [restart]: Move up to before the
        NULL test.

gcc/testsuite/ChangeLog:

        * g++.dg/cpp2a/concepts-requires30.C: New test.
---
  gcc/c-family/c-common.cc                         |  2 +-
  gcc/testsuite/g++.dg/cpp2a/concepts-requires30.C | 10 ++++++++++
  2 files changed, 11 insertions(+), 1 deletion(-)
  create mode 100644 gcc/testsuite/g++.dg/cpp2a/concepts-requires30.C

diff --git a/gcc/c-family/c-common.cc b/gcc/c-family/c-common.cc
index 70f55f3a346..bb0544eeaea 100644
--- a/gcc/c-family/c-common.cc
+++ b/gcc/c-family/c-common.cc
@@ -2009,12 +2009,12 @@ verify_tree (tree x, struct tlist **pbefore_sp, struct 
tlist **pno_sp,
    enum tree_code code;
    enum tree_code_class cl;

+ restart:

    /* X may be NULL if it is the operand of an empty statement expression
       ({ }).  */
    if (x == NULL)
      return;

- restart:

    code = TREE_CODE (x);
    cl = TREE_CODE_CLASS (code);

diff --git a/gcc/testsuite/g++.dg/cpp2a/concepts-requires30.C b/gcc/testsuite/g++.dg/cpp2a/concepts-requires30.C

new file mode 100644
index 00000000000..f500af3f616
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp2a/concepts-requires30.C
@@ -0,0 +1,10 @@
+// PR c++/105304
+// { dg-do compile { target c++20 } }
+// { dg-additional-options "-Wall -Wsequence-point" }
+
+struct A { };
+
+int main() {
+  if (requires { A(); })
+    ;
+}