[pushed] c++: result location and explicit inst [PR108496]

[pushed] c++: result location and explicit inst [PR108496]

[Jason Merrill]

Tested x86_64-pc-linux-gnu, applying to trunk.

-- 8< --

In r13-4469 we started to build the RESULT_DECL in grokdeclarator, while we
still know the location of the return type.  But in this testcase, we hit
that code again when parsing the explicit instantiation, and clobber the
DECL_RESULT that was previously used in parsing the function.  So, only set
DECL_RESULT if it isn't already set.

	PR c++/108496

gcc/cp/ChangeLog:

	* decl.cc (grokdeclarator): Check whether DECL_RESULT is already
	set.

gcc/testsuite/ChangeLog:

	* g++.dg/template/explicit-instantiation5.C: New test.
---
 gcc/cp/decl.cc                                    |  6 +++++-
 .../g++.dg/template/explicit-instantiation5.C     | 15 +++++++++++++++
 2 files changed, 20 insertions(+), 1 deletion(-)
 create mode 100644 gcc/testsuite/g++.dg/template/explicit-instantiation5.C

diff --git a/gcc/cp/decl.cc b/gcc/cp/decl.cc
index 75ddf8016b5..d606b31d7a7 100644
--- a/gcc/cp/decl.cc
+++ b/gcc/cp/decl.cc
@@ -14776,7 +14776,9 @@ grokdeclarator (const cp_declarator *declarator,
       {
 	/* If we saw a return type, record its location.  */
 	location_t loc = declspecs->locations[ds_type_spec];
-	if (loc != UNKNOWN_LOCATION)
+	if (loc == UNKNOWN_LOCATION)
+	  /* Build DECL_RESULT in start_preparsed_function.  */;
+	else if (!DECL_RESULT (decl))
 	  {
 	    tree restype = TREE_TYPE (TREE_TYPE (decl));
 	    tree resdecl = build_decl (loc, RESULT_DECL, 0, restype);
@@ -14784,6 +14786,8 @@ grokdeclarator (const cp_declarator *declarator,
 	    DECL_IGNORED_P (resdecl) = 1;
 	    DECL_RESULT (decl) = resdecl;
 	  }
+	else if (funcdef_flag)
+	  DECL_SOURCE_LOCATION (DECL_RESULT (decl)) = loc;
       }
 
     /* Record constancy and volatility on the DECL itself .  There's
diff --git a/gcc/testsuite/g++.dg/template/explicit-instantiation5.C b/gcc/testsuite/g++.dg/template/explicit-instantiation5.C
new file mode 100644
index 00000000000..7bc007c8107
--- /dev/null
+++ b/gcc/testsuite/g++.dg/template/explicit-instantiation5.C
@@ -0,0 +1,15 @@
+// PR c++/108496
+
+struct S { long a, b, c; } s;
+
+template <int, typename>
+S foo (S);
+
+template <>
+S
+foo <0, long> (S)
+{
+  return s;
+}
+
+template S foo <0, long> (S);

base-commit: 208c6678c25bd9a11e6c5911a4c123cb6b7f3d6e
-- 
2.31.1