[PATCH] Fix PR c++/27100

[Patrick Palka]

The problem here is that duplicate_decls doesn't preserve the
DECL_PENDING_INLINE_P flag of the old decl in the new decl.  This
happens only when a friend function is defined inside a class and then
redeclared.  The initial definition sets the DECL_PENDING_INLINE_P flag,
but the subsequent redeclaration doesn't retain the flag.

This patch makes duplicate_decls retain the DECL_PENDING_INLINE_P flag
from the old decl to the new decl.

Bootstrapped + regtested on x86_64-pc-linux-gnu.  Does this look OK to
commit?

gcc/cp/ChangeLog:

        PR c++/27100
        * decl.c (duplicate_decls): Properly copy the
        DECL_PENDING_INLINE_P, DECL_PENDING_INLINE_INFO and
        DECL_SAVED_FUNCTION_DATA fields from OLDDECL to NEWDECL.

gcc/testsuite/ChangeLog:

        PR c++/27100
        * g++.dg/other/friend6.C: New test.
---
 gcc/cp/decl.c                        | 13 +++++++++++--
 gcc/testsuite/g++.dg/other/friend6.C | 15 +++++++++++++++
 2 files changed, 26 insertions(+), 2 deletions(-)
 create mode 100644 gcc/testsuite/g++.dg/other/friend6.C

diff --git a/gcc/cp/decl.c b/gcc/cp/decl.c
index c1ad52f..4f79c71 100644
--- a/gcc/cp/decl.c
+++ b/gcc/cp/decl.c
@@ -2375,8 +2375,17 @@ duplicate_decls (tree newdecl, tree olddecl, bool 
newdecl_is_friend)
        }
       else
        {
-         if (DECL_PENDING_INLINE_INFO (newdecl) == 0)
-           DECL_PENDING_INLINE_INFO (newdecl) = DECL_PENDING_INLINE_INFO 
(olddecl);
+         if (DECL_PENDING_INLINE_P (olddecl))
+           {
+             DECL_PENDING_INLINE_P (newdecl) = 1;
+             DECL_PENDING_INLINE_INFO (newdecl)
+               = DECL_PENDING_INLINE_INFO (olddecl);
+           }
+         else if (DECL_PENDING_INLINE_P (newdecl))
+           ;
+         else if (DECL_SAVED_FUNCTION_DATA (newdecl) == NULL)
+           DECL_SAVED_FUNCTION_DATA (newdecl)
+             = DECL_SAVED_FUNCTION_DATA (olddecl);
 
          DECL_DECLARED_INLINE_P (newdecl) |= DECL_DECLARED_INLINE_P (olddecl);
 
diff --git a/gcc/testsuite/g++.dg/other/friend6.C 
b/gcc/testsuite/g++.dg/other/friend6.C
new file mode 100644
index 0000000..5f593a1
--- /dev/null
+++ b/gcc/testsuite/g++.dg/other/friend6.C
@@ -0,0 +1,15 @@
+// PR c++/27100
+// This used to fail at link time with an "undefined reference to 'foo'" error.
+// { dg-do link }
+
+struct A
+{
+  friend void foo (const A&) { }
+  friend void foo (const A&);
+};
+
+int
+main ()
+{
+  foo (A ());
+}
-- 
2.8.1.231.g95ac767