[C++ PATCH] PR c++/89948 - ICE with break in statement-expr.

[Jason Merrill]

If 'jump_target' is local to this function and still set at the end, we can't
correctly evaluate it, and we don't need to try.

        * constexpr.c (cxx_eval_statement_list): Jumping out of a
        statement-expr is non-constant.

Tested x86_64-pc-linux-gnu, applying to trunk.
---
 gcc/cp/constexpr.c                    |  9 +++++++++
 gcc/testsuite/g++.dg/ext/stmtexpr23.C | 10 ++++++++++
 gcc/cp/ChangeLog                      |  6 ++++++
 3 files changed, 25 insertions(+)
 create mode 100644 gcc/testsuite/g++.dg/ext/stmtexpr23.C

diff --git a/gcc/cp/constexpr.c b/gcc/cp/constexpr.c
index 53854a8acd4..0ce5618a2fc 100644
--- a/gcc/cp/constexpr.c
+++ b/gcc/cp/constexpr.c
@@ -4153,6 +4153,15 @@ cxx_eval_statement_list (const constexpr_ctx *ctx, tree 
t,
       if (returns (jump_target) || breaks (jump_target))
        break;
     }
+  if (*jump_target && jump_target == &local_target)
+    {
+      /* We aren't communicating the jump to our caller, so give up.  We don't
+        need to support evaluation of jumps out of statement-exprs.  */
+      if (!ctx->quiet)
+       error_at (cp_expr_loc_or_loc (r, input_location),
+                 "statement is not a constant expression");
+      *non_constant_p = true;
+    }
   return r;
 }
 
diff --git a/gcc/testsuite/g++.dg/ext/stmtexpr23.C 
b/gcc/testsuite/g++.dg/ext/stmtexpr23.C
new file mode 100644
index 00000000000..c6aaea76f23
--- /dev/null
+++ b/gcc/testsuite/g++.dg/ext/stmtexpr23.C
@@ -0,0 +1,10 @@
+// PR c++/89948
+// { dg-options "" }
+
+void f ()
+{
+  int a = 0;
+  for (;;)
+    for (;a=+({break;1;});)
+      {}
+}
diff --git a/gcc/cp/ChangeLog b/gcc/cp/ChangeLog
index ad4dba46bfe..6bfd26c6a2e 100644
--- a/gcc/cp/ChangeLog
+++ b/gcc/cp/ChangeLog
@@ -1,3 +1,9 @@
+2019-04-04  Jason Merrill  <ja...@redhat.com>
+
+       PR c++/89948 - ICE with break in statement-expr.
+       * constexpr.c (cxx_eval_statement_list): Jumping out of a
+       statement-expr is non-constant.
+
 2019-04-04  Jason Merrill  <ja...@redhat.com>
 
        PR c++/89966 - error with non-type auto tparm.

base-commit: 1a08779b89cee120afe057ba013ad7e92e62798f
-- 
2.20.1