[Bug tree-optimization/62032] FAIL: vsnprintf-chk.c execution, -O2 -flto -fno-use-linker-plugin -flto-partition=none

["rguenther at suse dot de" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=62032

--- Comment #4 from rguenther at suse dot de <rguenther at suse dot de> ---
On Thu, 7 Aug 2014, amker.cheng at gmail dot com wrote:

> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=62032
> 
> --- Comment #3 from bin.cheng <amker.cheng at gmail dot com> ---
> I did some investigation and think it's a latent bug of lto which reveaded by
> r213585.
> 
> Before the revision, pass_fold_builtins::execute calls gimple_fold_builtins
> directly to fold __builtin___vsnprintf_chk (_26, _25, 0, 4294967295, "%d - %c",
> ap);.  It works fine by simplifying the builtin into __builtin_vsnprintf (_26,
> _25, "%d - %c", ap);.
> 
> After the revision, it calls to
> fold_stmt->gimple_fold_call->gimple_fold_builtin to do the job.  But before
> that, it calls gimple_call_builtin_p to verify that it IS a valid builtin call,
> which in turn calls gimple_builtin_call_types_compatible_p to check that types
> between parameter and argument match each other.  Well, the check fails on the
> last parameter/argument, as dumped below:
> 
> TREE_TYPE of ARGUMENT:
>  <record_type 0x7fc34cc9fc78 va_list SI
>     size <integer_cst 0x7fc34ce71dc8 type <integer_type 0x7fc34ce7c0a8
> bitsizetype> constant 32>
>     unit size <integer_cst 0x7fc34ce71de0 type <integer_type 0x7fc34ce7c000
> sizetype> constant 4>
>     align 32 symtab 0 alias set -1 canonical type 0x7fc34ce899d8
>     fields <field_decl 0x7fc34ce87130 __ap
>         type <pointer_type 0x7fc34ce84000 type <void_type 0x7fc34ce7cf18 void>
>             public unsigned SI size <integer_cst 0x7fc34ce71dc8 32> unit size
> <integer_cst 0x7fc34ce71de0 4>
>             align 32 symtab 0 alias set 3 canonical type 0x7fc34ce84000
>             pointer_to_this <pointer_type 0x7fc34ce8a348>>
>         unsigned SI file <built-in> line 0 col 0 size <integer_cst
> 0x7fc34ce71dc8 32> unit size <integer_cst 0x7fc34ce71de0 4>
>         align 32 offset_align 64
>         offset <integer_cst 0x7fc34ce71df8 constant 0>
>         bit offset <integer_cst 0x7fc34ce71e58 constant 0> context <record_type
> 0x7fc34ce899d8 __va_list>> context <translation_unit_decl 0x7fc34df310f0
> D.4035>
>     pointer_to_this <pointer_type 0x7fc34ccaa2a0> chain <type_decl
> 0x7fc34ce87da8 __va_list>>
> 
> TREE_TYPE of PARAMETER of function BUILT_IN_VSNPRINTF_CHK:
>  <reference_type 0x7fc34ce89c78
>     type <record_type 0x7fc34ce899d8 __va_list SI
>         size <integer_cst 0x7fc34ce71dc8 constant 32>
>         unit size <integer_cst 0x7fc34ce71de0 constant 4>
>         align 32 symtab 0 alias set 7 canonical type 0x7fc34ce899d8
>         fields <field_decl 0x7fc34ce87130 __ap type <pointer_type
> 0x7fc34ce84000>
>             unsigned SI file <built-in> line 0 col 0 size <integer_cst
> 0x7fc34ce71dc8 32> unit size <integer_cst 0x7fc34ce71de0 4>
>             align 32 offset_align 64
>             offset <integer_cst 0x7fc34ce71df8 constant 0>
>             bit offset <integer_cst 0x7fc34ce71e58 constant 0> context
> <record_type 0x7fc34ce899d8 __va_list>>
>         pointer_to_this <pointer_type 0x7fc34ccc4888> reference_to_this
> <reference_type 0x7fc34ccaa0a8> chain <type_decl 0x7fc34ce87098 __va_list>>
>     unsigned SI size <integer_cst 0x7fc34ce71dc8 32> unit size <integer_cst
> 0x7fc34ce71de0 4>
>     align 32 symtab 0 alias set -1 canonical type 0x7fc34ce89c78>
> 
> 
> The root cause lies in gcc/lto/lto-lang.c:lto_init, there is below code
> snippet:
> 
>   if (TREE_CODE (va_list_type_node) == ARRAY_TYPE)
>     {
>       tree x = build_pointer_type (TREE_TYPE (va_list_type_node));
>       lto_define_builtins (x, x);
>     }
>   else
>     {
>       lto_define_builtins (va_list_type_node,
>                build_reference_type (va_list_type_node));
>     }
> 
> While prototype of lto_define_builtins is like below.
> static void
> lto_define_builtins (tree va_list_ref_type_node ATTRIBUTE_UNUSED,
>              tree va_list_arg_type_node ATTRIBUTE_UNUSED);
> 
> Apparently, the arguments passed to lto_define_builtins are mis-matched.  In
> fact, I think it should be consistent with function calls to c_define_builtins
> in c front-end.
> 
> I think above analysis also explains why it happens only with lto.
> 
> I will send a patch fixing this soon.

Thanks for the detective work!  IMHO this fix is worth backporting
to at least 4.9.

Richard.