Re: [PING^2][PATCH] libgcc, emutls: Allow building weak definitions of the emutls functions.
Iain Sandoe writes:
> Hi,
>
> So let’s ignore the questions for now - OK for the non-Darwin parts of the
> patch ?
Looks OK to me.
Thanks,
Richard
>
>> On 24 Sep 2021, at 17:57, Iain Sandoe wrote:
>>
>
>> as noted below the non-Darwin parts of this are trivial (and a no-OP).
>> I’d like to apply this to start work towards solving Darwin’s libgcc issues,
>
>>> On 20 Sep 2021, at 09:25, Iain Sandoe wrote:
>>>
>
>>> The non-Darwin part of this patch is trivial but raises a couple of
>>> questions
>>>
>>> A/
>>> We define builtins to support emulated TLS.
>>> These are defined with void * pointers
>>> The implementation (in libgcc) uses the correct type (struct
>>> __emutls_object *)
>>> in both a forward declaration of the functions and in thier eventual
>>> implementation.
>>>
>>> This leads to a (long-standing, nothing new) complaint at build-time about
>>> the mismatch in the builtin/implementation decls.
>>>
>>> AFAICT, there’s no way to fix that unless we introduce struct
>>> __emutls_object *
>>> as a built-in type?
>>>
>>> B/
>>> It seems that a consequence of the mismatch in decls means that if I apply
>>> attributes to the decl (in the implementation file), they are ignored and I
>>> have
>>> to apply them to the definition in order for this to work.
>>>
>>> This (B) is what the patch below does.
>>>
>>> tested on powerpc,i686,x86_64-darwin, x86_64-linux
>>> OK for master?
>>> thanks,
>>> Iain
>>>
>>> If the current situation is that A or B indicates “there’s a bug”, please
>>> could that
>>> be considered as distinct from the current patch (which doesn’t alter this
>>> in any
>>> way) so that we can make progress on fixing Darwin libgcc issues.
>>>
>>> = commit log
>>>
>>> In order to better support use of the emulated TLS between objects with
>>> DSO dependencies and static-linked libgcc, allow a target to make weak
>>> definitions.
>>>
>>> Signed-off-by: Iain Sandoe
>>>
>>> libgcc/ChangeLog:
>>>
>>> * config.host: Add weak-defined emutls crt.
>>> * config/t-darwin: Build weak-defined emutls objects.
>>> * emutls.c (__emutls_get_address): Add optional attributes.
>>> (__emutls_register_common): Likewise.
>>> (EMUTLS_ATTR): New.
>>> ---
>>> libgcc/config.host | 2 +-
>>> libgcc/config/t-darwin | 13 +
>>> libgcc/emutls.c| 17 +++--
>>> 3 files changed, 29 insertions(+), 3 deletions(-)
>>>
>>> diff --git a/libgcc/config.host b/libgcc/config.host
>>> index 6c34b13d611..a447ac7ae30 100644
>>> --- a/libgcc/config.host
>>> +++ b/libgcc/config.host
>>> @@ -215,7 +215,7 @@ case ${host} in
>>> *-*-darwin*)
>>> asm_hidden_op=.private_extern
>>> tmake_file="$tmake_file t-darwin ${cpu_type}/t-darwin t-libgcc-pic
>>> t-slibgcc-darwin"
>>> - extra_parts="crt3.o libd10-uwfef.a crttms.o crttme.o"
>>> + extra_parts="crt3.o libd10-uwfef.a crttms.o crttme.o libemutls_w.a"
>>> ;;
>>> *-*-dragonfly*)
>>> tmake_file="$tmake_file t-crtstuff-pic t-libgcc-pic t-eh-dw2-dip"
>>> diff --git a/libgcc/config/t-darwin b/libgcc/config/t-darwin
>>> index 14ae6b35a4e..d6f688d66d5 100644
>>> --- a/libgcc/config/t-darwin
>>> +++ b/libgcc/config/t-darwin
>>> @@ -15,6 +15,19 @@ crttme.o: $(srcdir)/config/darwin-crt-tm.c
>>> LIB2ADDEH = $(srcdir)/unwind-dw2.c $(srcdir)/config/unwind-dw2-fde-darwin.c
>>> \
>>> $(srcdir)/unwind-sjlj.c $(srcdir)/unwind-c.c
>>>
>>> +# Make emutls weak so that we can deal with -static-libgcc, override the
>>> +# hidden visibility when this is present in libgcc_eh.
>>> +emutls.o: HOST_LIBGCC2_CFLAGS += \
>>> + -DEMUTLS_ATTR='__attribute__((__weak__,__visibility__("default")))'
>>> +emutls_s.o: HOST_LIBGCC2_CFLAGS += \
>>> + -DEMUTLS_ATTR='__attribute__((__weak__,__visibility__("default")))'
>>> +
>>> +# Make the emutls crt as a convenience lib so that it can be linked
>>> +# optionally, use the shared version so that we can link with DSO.
>>> +libemutls_w.a: emutls_s.o
>>> + $(AR_CREATE_FOR_TARGET) $@ $<
>>> + $(RANLIB_FOR_TARGET) $@
>>> +
>>> # Patch to __Unwind_Find_Enclosing_Function for Darwin10.
>>> d10-uwfef.o: $(srcdir)/config/darwin10-unwind-find-enc-func.c
>>> $(crt_compile) -mmacosx-version-min=10.6 -c $<
>>> diff --git a/libgcc/emutls.c b/libgcc/emutls.c
>>> index ed2658170f5..d553a74728f 100644
>>> --- a/libgcc/emutls.c
>>> +++ b/libgcc/emutls.c
>>> @@ -50,7 +50,16 @@ struct __emutls_array
>>> void **data[];
>>> };
>>>
>>> +/* EMUTLS_ATTR is provided to allow targets to build the emulated tls
>>> + routines as weak definitions, for example.
>>> + If there is no definition, fall back to the default. */
>>> +#ifndef EMUTLS_ATTR
>>> +# define EMUTLS_ATTR
>>> +#endif
>>> +
>>> +EMUTLS_ATTR
>>> void *__emutls_get_address (struct __emutls_object *);
>>> +EMUTLS_ATTR
>>> void __emutls_register_common (struct __emutls_object *, word, word, void
>>> *);
>>>
>>> #ifdef __GTHREADS
>>> @@ -123,7 +132,11 @@ emutls_alloc (struct __emutls_object *obj)
>>> return ret;
>>> }
>>>
>>> -void *
>>>
Re: [PING^2][PATCH] libgcc, emutls: Allow building weak definitions of the emutls functions.
Hi,
So let’s ignore the questions for now - OK for the non-Darwin parts of the
patch ?
> On 24 Sep 2021, at 17:57, Iain Sandoe wrote:
>
> as noted below the non-Darwin parts of this are trivial (and a no-OP).
> I’d like to apply this to start work towards solving Darwin’s libgcc issues,
>> On 20 Sep 2021, at 09:25, Iain Sandoe wrote:
>>
>> The non-Darwin part of this patch is trivial but raises a couple of questions
>>
>> A/
>> We define builtins to support emulated TLS.
>> These are defined with void * pointers
>> The implementation (in libgcc) uses the correct type (struct __emutls_object
>> *)
>> in both a forward declaration of the functions and in thier eventual
>> implementation.
>>
>> This leads to a (long-standing, nothing new) complaint at build-time about
>> the mismatch in the builtin/implementation decls.
>>
>> AFAICT, there’s no way to fix that unless we introduce struct
>> __emutls_object *
>> as a built-in type?
>>
>> B/
>> It seems that a consequence of the mismatch in decls means that if I apply
>> attributes to the decl (in the implementation file), they are ignored and I
>> have
>> to apply them to the definition in order for this to work.
>>
>> This (B) is what the patch below does.
>>
>> tested on powerpc,i686,x86_64-darwin, x86_64-linux
>> OK for master?
>> thanks,
>> Iain
>>
>> If the current situation is that A or B indicates “there’s a bug”, please
>> could that
>> be considered as distinct from the current patch (which doesn’t alter this
>> in any
>> way) so that we can make progress on fixing Darwin libgcc issues.
>>
>> = commit log
>>
>> In order to better support use of the emulated TLS between objects with
>> DSO dependencies and static-linked libgcc, allow a target to make weak
>> definitions.
>>
>> Signed-off-by: Iain Sandoe
>>
>> libgcc/ChangeLog:
>>
>> * config.host: Add weak-defined emutls crt.
>> * config/t-darwin: Build weak-defined emutls objects.
>> * emutls.c (__emutls_get_address): Add optional attributes.
>> (__emutls_register_common): Likewise.
>> (EMUTLS_ATTR): New.
>> ---
>> libgcc/config.host | 2 +-
>> libgcc/config/t-darwin | 13 +
>> libgcc/emutls.c| 17 +++--
>> 3 files changed, 29 insertions(+), 3 deletions(-)
>>
>> diff --git a/libgcc/config.host b/libgcc/config.host
>> index 6c34b13d611..a447ac7ae30 100644
>> --- a/libgcc/config.host
>> +++ b/libgcc/config.host
>> @@ -215,7 +215,7 @@ case ${host} in
>> *-*-darwin*)
>> asm_hidden_op=.private_extern
>> tmake_file="$tmake_file t-darwin ${cpu_type}/t-darwin t-libgcc-pic
>> t-slibgcc-darwin"
>> - extra_parts="crt3.o libd10-uwfef.a crttms.o crttme.o"
>> + extra_parts="crt3.o libd10-uwfef.a crttms.o crttme.o libemutls_w.a"
>> ;;
>> *-*-dragonfly*)
>> tmake_file="$tmake_file t-crtstuff-pic t-libgcc-pic t-eh-dw2-dip"
>> diff --git a/libgcc/config/t-darwin b/libgcc/config/t-darwin
>> index 14ae6b35a4e..d6f688d66d5 100644
>> --- a/libgcc/config/t-darwin
>> +++ b/libgcc/config/t-darwin
>> @@ -15,6 +15,19 @@ crttme.o: $(srcdir)/config/darwin-crt-tm.c
>> LIB2ADDEH = $(srcdir)/unwind-dw2.c $(srcdir)/config/unwind-dw2-fde-darwin.c \
>> $(srcdir)/unwind-sjlj.c $(srcdir)/unwind-c.c
>>
>> +# Make emutls weak so that we can deal with -static-libgcc, override the
>> +# hidden visibility when this is present in libgcc_eh.
>> +emutls.o: HOST_LIBGCC2_CFLAGS += \
>> + -DEMUTLS_ATTR='__attribute__((__weak__,__visibility__("default")))'
>> +emutls_s.o: HOST_LIBGCC2_CFLAGS += \
>> + -DEMUTLS_ATTR='__attribute__((__weak__,__visibility__("default")))'
>> +
>> +# Make the emutls crt as a convenience lib so that it can be linked
>> +# optionally, use the shared version so that we can link with DSO.
>> +libemutls_w.a: emutls_s.o
>> +$(AR_CREATE_FOR_TARGET) $@ $<
>> +$(RANLIB_FOR_TARGET) $@
>> +
>> # Patch to __Unwind_Find_Enclosing_Function for Darwin10.
>> d10-uwfef.o: $(srcdir)/config/darwin10-unwind-find-enc-func.c
>> $(crt_compile) -mmacosx-version-min=10.6 -c $<
>> diff --git a/libgcc/emutls.c b/libgcc/emutls.c
>> index ed2658170f5..d553a74728f 100644
>> --- a/libgcc/emutls.c
>> +++ b/libgcc/emutls.c
>> @@ -50,7 +50,16 @@ struct __emutls_array
>> void **data[];
>> };
>>
>> +/* EMUTLS_ATTR is provided to allow targets to build the emulated tls
>> + routines as weak definitions, for example.
>> + If there is no definition, fall back to the default. */
>> +#ifndef EMUTLS_ATTR
>> +# define EMUTLS_ATTR
>> +#endif
>> +
>> +EMUTLS_ATTR
>> void *__emutls_get_address (struct __emutls_object *);
>> +EMUTLS_ATTR
>> void __emutls_register_common (struct __emutls_object *, word, word, void *);
>>
>> #ifdef __GTHREADS
>> @@ -123,7 +132,11 @@ emutls_alloc (struct __emutls_object *obj)
>> return ret;
>> }
>>
>> -void *
>> +/* Despite applying the attribute to the declaration, in this case the mis-
>> + match between the builtin's declaration [void * (*)(void *)] and the
>> + implementation here, causes the decl.
