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Re: r196201 - in /trunk: gcc/ChangeLog gcc/config/i...


On Thu, Feb 21, 2013 at 5:21 PM, Jakub Jelinek <jakub@redhat.com> wrote:
> On Thu, Feb 21, 2013 at 05:15:51PM +0400, Konstantin Serebryany wrote:
>> This commit breaks the build if the BFD linker is used (I have gold on
>> my box, so I missed it).
>>
>> Short repro:
>> % cat preinit.cc
>> void foo() {}
>> __attribute__((section(".preinit_array")))  void (*xxx)(void) = foo;
>> % g++ preinit.cc -shared # gold
>> % sudo apt-get remove  binutils-gold
>> ...
>> % g++ preinit.cc -shared # bfd
>> /usr/bin/ld: /tmp/cc4GVflE.o: .preinit_array section is not allowed in DSO
>> /usr/bin/ld: failed to set dynamic section sizes: Nonrepresentable
>> section on output
>> collect2: ld returned 1 exit status
>> %
>>
>> Can we stop building the asan-rt as DSO and leave only the static
>> variant (as in clang)?
>
> No, IMNSHO it is desirable to support also that.

It may cause I more trouble (we've seen a couple of bugs already) then do good.
Anyway, we can get rid of this later.

>
> Here is a different fix, so libasan.so will not have .preinit_array, but
> libasan.a will have it.  Ideally, that hunk should go into a separate
> source file (asan_preinit.cc ?), be just compiled into an object file,
> rather than shared library and the compiler driver should include it
> explicitly in the link.
>
> The used attribute is there because, as it isn't (or shouldn't) be exported
> out of the library, if libasan was built with LTO, it could very well be
> optimized away.
>
> 2013-02-21  Jakub Jelinek  <jakub@redhat.com>
>
>         * asan/asan_rtl.cc (__asan_preinit): Don't add if PIC macro is
>         defined.  Add used attribute.
>
> --- libsanitizer/asan/asan_rtl.cc.jj    2013-02-21 14:10:41.000000000 +0100
> +++ libsanitizer/asan/asan_rtl.cc       2013-02-21 14:16:28.985547506 +0100
> @@ -520,11 +520,11 @@ void __asan_init() {
>    }
>  }
>
> -#if ASAN_USE_PREINIT_ARRAY
> +#if ASAN_USE_PREINIT_ARRAY && !defined (PIC)
>    // On Linux, we force __asan_init to be called before anyone else
>    // by placing it into .preinit_array section.
>    // FIXME: do we have anything like this on Mac?
> -  __attribute__((section(".preinit_array")))
> +  __attribute__((section(".preinit_array"), used))
>    void (*__asan_preinit)(void) =__asan_init;
>  #elif defined(_WIN32) && defined(_DLL)
>    // On Windows, when using dynamic CRT (/MD), we can put a pointer

Thanks!
May I ask you to commit this to gcc (I have to run away now)?
I'll put this into upstream (maybe with asan_preinit.cc as you
suggest) tomorrow.

--kcc

>
>
>         Jakub


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