[gcc/devel/omp/gcc-9] cgraph: A COMDAT decl always has non-zero address.

[Tobias Burnus]

https://gcc.gnu.org/g:f2f70af7c52720a0905a455425de0d6ca4fb1dc4

commit f2f70af7c52720a0905a455425de0d6ca4fb1dc4
Author: Jason Merrill <jason@redhat.com>
Date:   Wed Feb 26 13:03:23 2020 -0500

    cgraph: A COMDAT decl always has non-zero address.
    
    We should be able to assume that a template instantiation or other COMDAT
    has non-zero address even if MAKE_DECL_ONE_ONLY for the target sets
    DECL_WEAK and we haven't yet decided to emit a definition in this
    translation unit.
    
    gcc/ChangeLog
    2020-02-26  Jason Merrill  <jason@redhat.com>
    
    	PR c++/92003
    	* symtab.c (symtab_node::nonzero_address): A DECL_COMDAT decl has
    	non-zero address even if weak and not yet defined.

Diff:
---
 gcc/ChangeLog                                   |  6 ++++++
 gcc/symtab.c                                    | 10 +++++-----
 gcc/testsuite/g++.dg/cpp0x/constexpr-static13.C | 17 +++++++++++++++++
 3 files changed, 28 insertions(+), 5 deletions(-)

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index fedf2aa..c4124fa 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,9 @@
+2020-02-26  Jason Merrill  <jason@redhat.com>
+
+	PR c++/92003
+	* symtab.c (symtab_node::nonzero_address): A DECL_COMDAT decl has
+	non-zero address even if weak and not yet defined.
+
 2020-02-26  Jiufu Guo  <guojiufu@linux.ibm.com>
 
 	PR target/93047
diff --git a/gcc/symtab.c b/gcc/symtab.c
index 33b4be7..9a6a1ea 100644
--- a/gcc/symtab.c
+++ b/gcc/symtab.c
@@ -1955,22 +1955,22 @@ symtab_node::nonzero_address ()
      bind to NULL. This is on by default on embedded targets only.
 
      Otherwise all non-WEAK symbols must be defined and thus non-NULL or
-     linking fails.  Important case of WEAK we want to do well are comdats.
-     Those are handled by later check for definition.
+     linking fails.  Important case of WEAK we want to do well are comdats,
+     which also must be defined somewhere.
 
      When parsing, beware the cases when WEAK attribute is added later.  */
-  if (!DECL_WEAK (decl)
+  if ((!DECL_WEAK (decl) || DECL_COMDAT (decl))
       && flag_delete_null_pointer_checks)
     {
       refuse_visibility_changes = true;
       return true;
     }
 
-  /* If target is defined and either comdat or not extern, we know it will be
+  /* If target is defined and not extern, we know it will be
      output and thus it will bind to non-NULL.
      Play safe for flag_delete_null_pointer_checks where weak definition may
      be re-defined by NULL.  */
-  if (definition && (!DECL_EXTERNAL (decl) || DECL_COMDAT (decl))
+  if (definition && !DECL_EXTERNAL (decl)
       && (flag_delete_null_pointer_checks || !DECL_WEAK (decl)))
     {
       if (!DECL_WEAK (decl))
diff --git a/gcc/testsuite/g++.dg/cpp0x/constexpr-static13.C b/gcc/testsuite/g++.dg/cpp0x/constexpr-static13.C
new file mode 100644
index 0000000..644f9f7
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/constexpr-static13.C
@@ -0,0 +1,17 @@
+// PR c++/92003
+// { dg-do compile { target c++11 } }
+// { dg-prune-output "narrowing conversion" }
+
+constexpr char const* get_c_str() { return "abc"; }
+constexpr bool use_get_c_str_in_constexpr_context{get_c_str()}; // works
+
+template <char... Cs>
+struct string {
+  static constexpr char const* c_str() { return c; }
+
+ private:
+  static constexpr char c[]{Cs..., '\0'};
+};
+
+constexpr char const* cstr{string<'a', 'b', 'c'>::c_str()};
+constexpr bool use_cstr_in_constexpr_context{cstr}; // doesn't work