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Re: [patch] Fix GC issue triggered by arithmetic overflow checking
- From: Richard Biener <richard dot guenther at gmail dot com>
- To: Eric Botcazou <ebotcazou at adacore dot com>
- Cc: GCC Patches <gcc-patches at gcc dot gnu dot org>
- Date: Mon, 10 Oct 2016 12:48:48 +0200
- Subject: Re: [patch] Fix GC issue triggered by arithmetic overflow checking
- Authentication-results: sourceware.org; auth=none
- References: <1863165.r8qPLI7fxq@polaris> <CAFiYyc2ac_zXHz1yqPrzvqrwKYu2_LLropU4RAHxvPpXLmZRMw@mail.gmail.com> <2004625.PcKOVMIpSq@polaris>
On Mon, Oct 10, 2016 at 12:38 PM, Eric Botcazou <ebotcazou@adacore.com> wrote:
>> I believe the rule is that you might only depend on the order of objects
>> with respect to their DECL_UID, not the actual value of the DECL_UID.
>> As var-tracking shouldn't look at TYPE_DECLs (?) it's probably a latent
>> var-tracking bug as well.
>
> It presumably doesn't look at TYPE_DECLs, simply the DECL_UID of variables is
> also different so this changes some hashing.
Yes. But that's not the only source for DECL_UID differences. Btw,
I see lots of FOR_EACH_HASH_TABLE_ELEMENT in var-tracking.c
but they don't look like their outcome is supposed to be dependent on
element ordering.
Did you track down where exactly the code-gen difference appeared?
>> I'd prefer the named parameter to be defaulted to false and the few
>> places in the FEs fixed (eventually that name business should be
>> handled like names for nodes like integer_type_node -- I see no
>> reason why build_complex_type should have this special-case at all!
>> That is, why are the named vairants in the type hash in the first place?)
>
> I think that the calls in build_common_tree_nodes need to be changed too then:
>
> complex_integer_type_node = build_complex_type (integer_type_node);
> complex_float_type_node = build_complex_type (float_type_node);
> complex_double_type_node = build_complex_type (double_type_node);
> complex_long_double_type_node = build_complex_type (long_double_type_node);
>
> in addition to:
>
> ./ada/gcc-interface/decl.c: = build_complex_type
> ./ada/gcc-interface/decl.c: return build_complex_type (nt);
> ./ada/gcc-interface/trans.c: tree gnu_ctype = build_complex_type
> (gnu_type);
> ./c/c-decl.c: specs->type = build_complex_type (specs->type);
> ./c/c-decl.c: specs->type = build_complex_type (specs->type);
> ./c/c-decl.c: specs->type = build_complex_type (specs->type);
> ./c/c-parser.c: build_complex_type
> ./c/c-typeck.c: return build_complex_type (subtype);
> ./c-family/c-common.c: return build_complex_type (inner_type);
> ./c-family/c-lex.c: type = build_complex_type (type);
> ./cp/decl.c: type = build_complex_type (type);
> ./cp/typeck.c: return build_type_attribute_variant (build_complex_type
> (subtype),
> ./fortran/trans-types.c:gfc_build_complex_type (tree scalar_type)
> ./fortran/trans-types.c: type = gfc_build_complex_type (type);
> ./go/go-gcc.cc:
> build_complex_type(TREE_TYPE(real_tree)),
> ./go/go-gcc.cc: type = build_complex_type(type);
> ./lto/lto-lang.c: return build_complex_type (inner_type);
>
> Or perhaps *only* the calls in build_common_tree_nodes need to be changed?
>
> It's certainly old code (r29604, September 1999).
>
> --
> Eric Botcazou