[Bug gold/19577] Gold failed to build with GCC 5.3

[ccoutant at gmail dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=19577

--- Comment #8 from Cary Coutant <ccoutant at gmail dot com> ---
Sorry, that patch was stale. Here's the correct version.

-cary


On Sat, Feb 6, 2016 at 5:55 PM, Cary Coutant <address@hidden> wrote:
>> /export/gnu/import/git/sources/binutils-gdb/gold/reloc.h:1009:37: error:
>> integer overflow in expression [-Werror=overflow]
>>      int32_t max = (1 << (bits - 1)) - 1;
>>                                      ^
>
>> /export/gnu/import/git/sources/binutils-gdb/gold/reloc.h:1023:46: error: left
>> shift count >= width of type [-Werror=shift-count-overflow]
>>      uint32_t max = static_cast<uint32_t>((1U << bits) - 1);
>
> Hmmm, in both of these cases, I'd have expected the compiler to do
> enough constant propagation to see that the code it's complaining
> about is dead when bits == 32.
>
> Here's a patch that I think makes the code both clearer and more 
> compiler-proof.
>
> I'm having trouble doing a full build with the trunk compiler, but I
> did do some testing on the side to try to make sure this code compiles
> clean and correctly. (I'm running stock Ubuntu on a VM, with GCC 4.8.2
> installed. And no multilib either.)
>
> -cary
>
>
> 2016-02-06  Cary Coutant  <address@hidden>
>
> gold/
>         * reloc.h (Limits): New class.
>         (Bits::has_overflow32): Use min/max values from Limits.
>         (Bits::has_unsigned_overflow32): Likewise.
>         (Bits::has_signed_unsigned_overflow32): Likewise.
>         (Bits::has_overflow): Likewise.
>         (Bits::has_unsigned_overflow): Likewise.
>         (Bits::has_signed_unsigned_overflow64): Likewise.

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