[Bug c++/44871] Invalid type mismatches while merging C and C++ sources

[Bug c++/44871] Invalid type mismatches while merging C and C++ sources

[hubicka at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=44871

Jan Hubicka <hubicka at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Last reconfirmed|2010-07-08 14:47:48         |2010-10-02 14:47:48

--- Comment #10 from Jan Hubicka <hubicka at gcc dot gnu.org> 2010-10-02 14:12:02 UTC ---
reconfirmed.

[Bug c++/44871] Invalid type mismatches while merging C and C++ sources

[hubicka at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=44871

--- Comment #11 from Jan Hubicka <hubicka at gcc dot gnu.org> 2010-10-15 02:39:00 UTC ---
Richard, any hope for a clean fix or shall we go with the hack above for next
release?

[Bug c++/44871] Invalid type mismatches while merging C and C++ sources

[rguenth at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=44871

--- Comment #12 from Richard Guenther <rguenth at gcc dot gnu.org> 2010-11-26 16:29:53 UTC ---
I'd like to hear opinions from C and C++ FE people as to why the current
state illustrated in comment #6 makes sense and if the behavior can be
commonized between C and C++.

I might be that the current difference in behavior is mandated by some
standards.

We can now also fix this in LTO by making sure we at least get the
same TYPE_CANONICAL.  I will try to look at how difficult that would
be.

[Bug c++/44871] Invalid type mismatches while merging C and C++ sources

[rguenth at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=44871

--- Comment #13 from Richard Guenther <rguenth at gcc dot gnu.org> 2010-11-26 17:06:25 UTC ---
Testcase:

> cat gcc/testsuite/g++.dg/lto/20101126-1_0.C
typedef struct { int i; } T1;
typedef T1 T2;
extern T1 a;
extern T2 b;
int main() { return a.i + b.i; }

> cat gcc/testsuite/g++.dg/lto/20101126-1_1.c
typedef struct { int i; } T1;
typedef T1 T2;
T1 a;
T2 b;

/space/rguenther/src/svn/trunk/gcc/testsuite/g++.dg/lto/20101126-1_0.C:3:11:
warning: type of 'a' does not match original declaration [enabled by default]^M
/space/rguenther/src/svn/trunk/gcc/testsuite/g++.dg/lto/20101126-1_1.c:3:4:
note: previously declared here^M
/space/rguenther/src/svn/trunk/gcc/testsuite/g++.dg/lto/20101126-1_0.C:4:11:
warning: type of 'b' does not match original declaration [enabled by default]^M
/space/rguenther/src/svn/trunk/gcc/testsuite/g++.dg/lto/20101126-1_1.c:4:4:
note: previously declared here^M

(gdb) call debug_tree (prevailing->decl)
 <var_decl 0x7ffff5d071e0 a
    type <record_type 0x7ffff5d083f0 T1 SI
        size <integer_cst 0x7ffff7ed36e0 constant 32>
        unit size <integer_cst 0x7ffff7ed33e8 constant 4>
        align 32 symtab 0 alias set -1 structural equality
        fields <field_decl 0x7ffff7edbda8 i type <integer_type 0x7ffff7ee3498>
            nonlocal SI file t4.ii line 1 col 22 size <integer_cst
0x7ffff7ed36e0 32> unit size <integer_cst 0x7ffff7ed33e8 4>
            align 32 offset_align 128
            offset <integer_cst 0x7ffff7ed3410 constant 0>
            bit offset <integer_cst 0x7ffff7ed3b18 constant 0> context
<record_type 0x7ffff5d083f0 T1>>>
    public static SI file t4.ii line 3 col 4 size <integer_cst 0x7ffff7ed36e0
32> unit size <integer_cst 0x7ffff7ed33e8 4>
    align 32 context <translation_unit_decl 0x7ffff7edde60 D.2010>>
(gdb) call debug_tree (decl)
 <var_decl 0x7ffff5d07000 a
    type <record_type 0x7ffff5d080a8 SI
        size <integer_cst 0x7ffff7ed36e0 constant 32>
        unit size <integer_cst 0x7ffff7ed33e8 constant 4>
        align 32 symtab 0 alias set -1 structural equality
        fields <field_decl 0x7ffff7edbd10 i type <integer_type 0x7ffff7ee3498>
            SI file t3.i line 1 col 22 size <integer_cst 0x7ffff7ed36e0 32>
unit size <integer_cst 0x7ffff7ed33e8 4>
            align 32 offset_align 128
            offset <integer_cst 0x7ffff7ed3410 constant 0>
            bit offset <integer_cst 0x7ffff7ed3b18 constant 0> context
<record_type 0x7ffff5d080a8>>>
    used public external common SI file t3.i line 3 col 11 size <integer_cst
0x7ffff7ed36e0 32> unit size <integer_cst 0x7ffff7ed33e8 4>
    align 32 context <translation_unit_decl 0x7ffff7eddb80 D.2001>>


if we want to have the same canonical type for the above we can simply
disregard all names, which makes sense for canonical type merging, but
that makes the hash functions very weak again (we share the type hashes
for type and canonical type merging).  It also can run foul of too much
merging when facing incomplete types which can happen in various places.

[Bug c++/44871] Invalid type mismatches while merging C and C++ sources

[joseph at codesourcery dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=44871

--- Comment #14 from joseph at codesourcery dot com <joseph at codesourcery dot com> 2010-11-26 18:40:15 UTC ---
On Fri, 26 Nov 2010, rguenth at gcc dot gnu.org wrote:

> I'd like to hear opinions from C and C++ FE people as to why the current
> state illustrated in comment #6 makes sense and if the behavior can be
> commonized between C and C++.

C++ has special rules about using typedefs for anonymous structure types 
for linkage purposes.  C has no such rules.  Thus, for C you can have

typedef struct { int a; } T1;
void f(T1);

in one translation unit and

typedef struct { int a; } T2;
void f(T2);

in another and they refer to the same function (cross-translation-unit 
struct compatibility rules apply) - for C++ they do not (and are mangled 
differently).

[Bug c++/44871] Invalid type mismatches while merging C and C++ sources

[rguenth at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=44871

Richard Guenther <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|                            |FIXED

--- Comment #16 from Richard Guenther <rguenth at gcc dot gnu.org> 2010-12-02 12:25:40 UTC ---
Fixed.

[Bug c++/44871] Invalid type mismatches while merging C and C++ sources

[rguenth at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=44871

--- Comment #15 from Richard Guenther <rguenth at gcc dot gnu.org> 2010-12-02 12:24:50 UTC ---
Author: rguenth
Date: Thu Dec  2 12:24:46 2010
New Revision: 167367

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=167367
Log:
2010-12-02  Richard Guenther  <rguenther@suse.de>

    PR lto/44871
    * gimple.c (canonical_type_hash_cache): New hashtable.
    (gimple_type_hash): Make a wrapper around ...
    (gimple_type_hash_1): ... this.  Take gtc_mode argument.
    (gimple_canonical_type_hash): Likewise.
    (gtc_visit): Take a gtc_mode argument.
    (gimple_types_compatible_p_1): Likewise. Do not compare struct
    tag names or field names when computing canonical types.
    (gimple_types_compatible_p): Adjust.
    (visit): Take a gtc_mode argument.
    (iterative_hash_gimple_type): Likewise.  Do not hash struct tag
    names or field names when computing hashes of canonical types.
    (gimple_register_canonical_type): Use gimple_canonical_type_hash
    for the hash.
    (print_gimple_types_stats): Dump stats of canonical_type_hash_cache.
    (free_gimple_type_tables): Free canonical_type_hash_cache.

    * g++.dg/lto/20101126-1_0.C: New testcase.
    * g++.dg/lto/20101126-1_1.c: Likewise.

Added:
    trunk/gcc/testsuite/g++.dg/lto/20101126-1_0.C
    trunk/gcc/testsuite/g++.dg/lto/20101126-1_1.c
Modified:
    trunk/gcc/ChangeLog
    trunk/gcc/gimple.c
    trunk/gcc/testsuite/ChangeLog

[Bug middle-end/44871] New: Invalid type mismatches while merging C and C++ sources

[hubicka at gcc dot gnu dot org]

[-- Warning: decoded text below may be mangled, UTF-8 assumed --]
[-- Attachment #1: Type: text/plain, Size: 1061 bytes --]

jh@evans:/abuild/jh/mozilla-central/build6/gfx/harfbuzz/src>
/abuild/jh/trunk-install/bin/gcc  -O2 -fwhopr  -r -nostdlib hb-blob.i -c
jh@evans:/abuild/jh/mozilla-central/build6/gfx/harfbuzz/src>
/abuild/jh/trunk-install/bin/g++  -O2 -fwhopr  -r -nostdlib *.ii -c
jh@evans:/abuild/jh/mozilla-central/build6/gfx/harfbuzz/src>
/abuild/jh/trunk-install/bin/g++ hb-blob.o -O2 -fwhopr  -r -nostdlib hb-font.o
../../../../gfx/harfbuzz/src/hb-blob-private.h:53:60: warning: type of
‘_hb_blob_nil’ does not match original declaration [enabled by default]
../../../../gfx/harfbuzz/src/hb-blob.c:45:11: note: previously declared here


-- 
           Summary: Invalid type mismatches while merging C and C++ sources
           Product: gcc
           Version: 4.6.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: middle-end
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: hubicka at gcc dot gnu dot org
  GCC host triplet: x86_64-linux


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=44871

[Bug c++/44871] Invalid type mismatches while merging C and C++ sources

[rguenth at gcc dot gnu dot org]

------- Comment #7 from rguenth at gcc dot gnu dot org  2010-07-09 12:42 -------
The hard part with changing the C frontend to behave like the C++ frontend
is to preserve the debug info for the typedef.

The C frontend consistently uses DECL_ORIGINAL_TYPE to refer to what a
TYPE_DECL was typedeffed to, but the C++ FE again does not use this
for typedef struct { } T1; (but it does for typedef struct X { } T1;).


-- 

rguenth at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
          Component|lto                         |c++


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=44871

[Bug c++/44871] Invalid type mismatches while merging C and C++ sources

[rguenth at gcc dot gnu dot org]

------- Comment #8 from rguenth at gcc dot gnu dot org  2010-07-09 12:52 -------
The only difference I see for typedef struct { } T1; vs typedef struct X { }
T1;
when looking at its main variant (or recursively DECL_ORIGINAL_TYPE) is

 <type_decl 0x7ffff5b2be60 X
    type <record_type 0x7ffff5b31dc8 X type_5 QI
        size <integer_cst 0x7ffff7ed24b0 constant 8>
        unit size <integer_cst 0x7ffff7ed24d8 constant 1>
        align 8 symtab 0 alias set -1 canonical type 0x7ffff5b31dc8
        fields <type_decl 0x7ffff5b2bf18 X type <record_type 0x7ffff5b31e70 X>
            nonlocal decl_4 VOID file t.i line 1 col 18
            align 1 context <record_type 0x7ffff5b31dc8 X> result <record_type
0x7ffff5b31dc8 X>
           >
        full-name "struct X"
        X() X(constX&) this=(X&) n_parents=0 use_template=0 interface-unknown
        chain <type_decl 0x7ffff5b2be60 X>>
    public decl_2 VOID file t.i line 1 col 16
    align 8 chain <function_decl 0x7ffff5b23e00 __cxa_call_unexpected>>

 <type_decl 0x7ffff5b43000 T1
    type <record_type 0x7ffff5b31dc8 T1 type_5 QI
        size <integer_cst 0x7ffff7ed24b0 constant 8>
        unit size <integer_cst 0x7ffff7ed24d8 constant 1>
        align 8 symtab 0 alias set -1 canonical type 0x7ffff5b31dc8
        fields <type_decl 0x7ffff5b2bf18 ._0 type <record_type 0x7ffff5b31e70
T1>
            nonlocal decl_4 VOID file t.i line 1 col 16
            align 1 context <record_type 0x7ffff5b31dc8 T1> result <record_type
0x7ffff5b31dc8 T1>
           >
        full-name "struct T1"
        X() X(constX&) this=(X&) n_parents=0 use_template=0 interface-unknown
        chain <type_decl 0x7ffff5b2be60 ._0>>
    VOID file t.i line 1 col 20
    align 1 chain <type_decl 0x7ffff5b2be60 ._0>>

which is the difference in alignment, TREE_PUBLIC and decl_lang_flag_2 set
(DECL_IMPLICIT_TYPEDEF_P).


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=44871

[Bug c++/44871] Invalid type mismatches while merging C and C++ sources

[rguenth at gcc dot gnu dot org]

------- Comment #9 from rguenth at gcc dot gnu dot org  2010-07-09 13:01 -------
The following seems to work at least for the testcase:

Index: gcc/tree.c
===================================================================
--- gcc/tree.c  (revision 161994)
+++ gcc/tree.c  (working copy)
@@ -4298,6 +4298,18 @@ free_lang_data_in_type (tree type)
     {
       tree prev, member;

+      if (strcmp (lang_hooks.name, "GNU C++") == 0)
+       {
+         /* If this isn't an implicit typedef then this final
+            non-typedef name is not a struct tag.  Clear its name.
+            See PR44871 for the glory details.  */
+         if (TYPE_NAME (type)
+             && TREE_CODE (TYPE_NAME (type)) == TYPE_DECL
+             && !DECL_ORIGINAL_TYPE (TYPE_NAME (type))
+             /* DECL_IMPLICIT_TYPEDEF_P */
+             && !DECL_LANG_FLAG_2 (TYPE_NAME (type)))
+           TYPE_NAME (type) = NULL_TREE;
+       }
       /* Note that TYPE_FIELDS can be shared across distinct
         TREE_TYPEs.  Therefore, if the first field of TYPE_FIELDS is
         to be removed, we cannot set its TREE_CHAIN to NULL.

it will wreck debuginfo for T1 of course.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=44871