From: Marek Polacek <polacek@redhat.com>
Date: Sat, 7 Dec 2019 17:35:54 +0000 (+0000)
Subject: PR c++/91678 - wrong error with decltype and location wrapper.
X-Git-Url: https://git.libre-soc.org/?a=commitdiff_plain;h=bfbe98c7e0d570c903c89359cd25073e538a365e;p=gcc.git

PR c++/91678 - wrong error with decltype and location wrapper.

Compiling this testcase results in a bogus "invalid cast" error; this occurs
since the introduction of location wrappers in finish_id_expression.

Here we are parsing the decltype expression via cp_parser_decltype_expr which
can lead to calling various fold_* and c-family routines.  They use
non_lvalue_loc, but that won't create a NON_LVALUE_EXPR wrapper around a location
wrapper.

So before the location wrappers addition cp_parser_decltype_expr would return
NON_LVALUE_EXPR <c>.  Now it returns VIEW_CONVERT_EXPR<float *>(c), but the
STRIP_ANY_LOCATION_WRAPPER immediately following it strips the location wrapper,
and suddenly we don't know whether we have an lvalue anymore.  And that's sad
because then decltype produces the wrong type, causing nonsense errors.

	* fold-const.c (maybe_lvalue_p): Handle VIEW_CONVERT_EXPR.

	* g++.dg/cpp0x/decltype73.C: New test.

From-SVN: r279077
---

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 582ffe09923..0994815f4a1 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,8 @@
+2019-12-07  Marek Polacek  <polacek@redhat.com>
+
+	PR c++/91678 - wrong error with decltype and location wrapper.
+	* fold-const.c (maybe_lvalue_p): Handle VIEW_CONVERT_EXPR.
+
 2019-12-07  Eric Botcazou  <ebotcazou@adacore.com>
 
 	PR middle-end/90840
diff --git a/gcc/fold-const.c b/gcc/fold-const.c
index c5bd45a6e34..8e9e299926a 100644
--- a/gcc/fold-const.c
+++ b/gcc/fold-const.c
@@ -2598,6 +2598,7 @@ maybe_lvalue_p (const_tree x)
   case TARGET_EXPR:
   case COND_EXPR:
   case BIND_EXPR:
+  case VIEW_CONVERT_EXPR:
     break;
 
   default:
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index 460cff00dd1..2d14412c7a7 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,8 @@
+2019-12-07  Marek Polacek  <polacek@redhat.com>
+
+	PR c++/91678 - wrong error with decltype and location wrapper.
+	* g++.dg/cpp0x/decltype73.C: New test.
+
 2019-12-07  Jakub Jelinek  <jakub@redhat.com>
 
 	PR c++/92831
diff --git a/gcc/testsuite/g++.dg/cpp0x/decltype73.C b/gcc/testsuite/g++.dg/cpp0x/decltype73.C
new file mode 100644
index 00000000000..cbe94a898e3
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/decltype73.C
@@ -0,0 +1,4 @@
+// PR c++/91678 - wrong error with decltype and location wrapper.
+// { dg-do compile { target c++11 } }
+
+float* test(float* c) { return (decltype(c + 0))(float*)c; }