[PATCH] Fix PR85176, LTO with -g1

[Richard Biener]

This fixes an issue with LTO handling DINFO_LEVEL_TERSE where we do
not generate DIEs for NAMESPACE_DECLs and thus reconstruction of the
DIE tree from DECL_CONTEXT at LTRANS time fails.  The fix is to
skip NAMESPACE_DECL contexts like we do for TYPE contexts.

[LTO with -g1] Bootstrapped on x86_64-unknown-linux-gnu, testing in
progress.

Richard.

2018-04-04  Richard Biener  <rguent...@suse.de>

        PR lto/85176
        * dwarf2out.c (dwarf2out_register_external_die): Peel namespaces
        from contexts for DINFO_LEVEL_TERSE and below.

        * g++.dg/lto/pr85176_0.C: New testcase.

Index: gcc/dwarf2out.c
===================================================================
--- gcc/dwarf2out.c     (revision 259069)
+++ gcc/dwarf2out.c     (working copy)
@@ -5903,8 +5903,13 @@ dwarf2out_register_external_die (tree de
     }
   else
     ctx = DECL_CONTEXT (decl);
+  /* Peel types in the context stack.  */
   while (ctx && TYPE_P (ctx))
     ctx = TYPE_CONTEXT (ctx);
+  /* Likewise namespaces in case we do not want to emit DIEs for them.  */
+  if (debug_info_level <= DINFO_LEVEL_TERSE)
+    while (ctx && TREE_CODE (ctx) == NAMESPACE_DECL)
+      ctx = DECL_CONTEXT (ctx);
   if (ctx)
     {
       if (TREE_CODE (ctx) == BLOCK)
Index: gcc/testsuite/g++.dg/lto/pr85176_0.C
===================================================================
--- gcc/testsuite/g++.dg/lto/pr85176_0.C        (nonexistent)
+++ gcc/testsuite/g++.dg/lto/pr85176_0.C        (working copy)
@@ -0,0 +1,10 @@
+// { dg-lto-do link }
+// { dg-lto-options { { -flto -g1 } } }
+// { dg-extra-ld-options "-r -nostdlib" }
+namespace a {
+    template <typename b, typename = b> class c;
+    template <typename b, typename d> void e(c<b, d> &);
+    void operator<<(c<char> &f, const char *) { e(f); }
+    extern c<char> cout;
+}
+int main() { a::cout << ""; }