PING: PATCH: PR target/46770: Use .init_array/.fini_array sections

On Fri, Jul 22, 2011 at 6:03 AM, H.J. Lu <hjl.tools@gmail.com> wrote:
> On Fri, Jul 22, 2011 at 5:30 AM, Jakub Jelinek <jakub@redhat.com> wrote:
>> On Fri, Jul 22, 2011 at 04:59:28AM -0700, H.J. Lu wrote:
>>> @@ -2660,6 +2664,7 @@ esac
>>>  case ${target} in
>>>  i[34567]86-*-linux* | x86_64-*-linux*)
>>>       tmake_file="${tmake_file} i386/t-pmm_malloc i386/t-i386"
>>> +     use_initfini_array=yes
>>>       ;;
>>>  i[34567]86-*-* | x86_64-*-*)
>>>       tmake_file="${tmake_file} i386/t-gmm_malloc i386/t-i386"
>>
>> What is i?86/x86_64 specific on it?  Don't most other glibc targets
>> want to use it too, perhaps with some arch specific tweaks?
>
> I do have a patch for all ELF targets:
>
> http://gcc.gnu.org/ml/gcc-patches/2011-06/msg01416.html
>
> It touches many targets. .  But I only have one feedback from one
> target maintainer.  I don't know how long it will take to review it.
>
>
>>> --- /dev/null
>>> +++ b/gcc/config/initfini-array.c
>>
>> This is ugly.  varasm.c already has lots of ELF specific code, simply
>> put them there as well and only let configury set some macro which will
>> allow targets to choose which of the implementations in the generic code
>> they want to use (or if they want their own which e.g. calls the generic
>> routine and does something additional to it etc.).  The sections probably
>> can be created only the first time you actually need them.
>
> I will do that.
>
>>> --- a/gcc/crtstuff.c
>>> +++ b/gcc/crtstuff.c
>>> @@ -189,6 +190,9 @@ typedef void (*func_ptr) (void);
>>>     refer to only the __CTOR_END__ symbol in crtend.o and the __DTOR_LIST__
>>>     symbol in crtbegin.o, where they are defined.  */
>>>
>>> +/* No need for .ctors/.dtors section if linker can place them in
>>> +   .init_array/.fini_array section.  */
>>> +#ifndef NO_CTORS_DTORS_SECTIONS
>>>  /* The -1 is a flag to __do_global_[cd]tors indicating that this table
>>>     does not start with a count of elements.  */
>>>  #ifdef CTOR_LIST_BEGIN
>>> @@ -219,6 +223,7 @@ STATIC func_ptr __DTOR_LIST__[1]
>>>    __attribute__((section(".dtors"), aligned(sizeof(func_ptr))))
>>>    = { (func_ptr) (-1) };
>>>  #endif /* __DTOR_LIST__ alternatives */
>>> +#endif /* NO_CTORS_DTORS_SECTIONS */
>>>
>>>  #ifdef USE_EH_FRAME_REGISTRY
>>>  /* Stick a label at the beginning of the frame unwind info so we can register
>>> @@ -489,6 +494,9 @@ __do_global_ctors_1(void)
>>>
>>>  #elif defined(CRT_END) /* ! CRT_BEGIN */
>>>
>>> +/* No need for .ctors/.dtors section if linker can place them in
>>> +   .init_array/.fini_array section.  */
>>> +#ifndef NO_CTORS_DTORS_SECTIONS
>>>  /* Put a word containing zero at the end of each of our two lists of function
>>>     addresses.  Note that the words defined here go into the .ctors and .dtors
>>>     sections of the crtend.o file, and since that file is always linked in
>>> @@ -534,6 +542,7 @@ STATIC func_ptr __DTOR_END__[1]
>>>    __attribute__((used, section(".dtors"), aligned(sizeof(func_ptr))))
>>>    = { (func_ptr) 0 };
>>>  #endif
>>> +#endif /* NO_CTORS_DTORS_SECTIONS */
>>>
>>>  #ifdef EH_FRAME_SECTION_NAME
>>>  /* Terminate the frame unwind info section with a 4byte 0 as a sentinel;
>>
>> I don't see how you can do this.  It would IMO break any time you link code
>> built by different gcc versions where some code emitted by the older gcc
>> used .ctors or .dtors.
>
> crtstuff.c is used to generate crt*.o, which is the part of GCC.  You only use
> it with the GCC you are using.  Since your GCC doesn't put anything in
> .ctors/.dtors section, you don't need them.  As for .o files generated by
> old GCCs, that is the linker test, use_initfini_array, is for.  The newer linker
> can put input .ctors/.dtors sections in output .init_array/,fini_array sections.
>
>

Here is the updated patch.  Any comments?

Thanks.

PING: PATCH: PR target/46770: Use .init_array/.fini_array sections

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Patch