Failed to build rescue with gcc 4.9

[Warner Losh]

> On Apr 3, 2015, at 2:39 PM, Ed Maste <emaste at freebsd.org> wrote:
> 
> On 3 April 2015 at 13:02, Warner Losh <imp at bsdimp.com> wrote:
>> That shows that something in the list is needed. Likely only crunchhide.
>> 
>> It doesn’t tell us why we need it, or when we started needing it, or what
>> other conditions we might need it. This information is critical to document
>> so we know when we can stop doing it in the future. I’m extremely reluctant
>> to commit this until we know these details.
> 
> Yes, it's crunchide. It was broken prior to r277259:
> 
> |    crunchide: Correct 64-bit section header offset
> |
> |    For 64-bit binaries the Elf_Ehdr e_shoff is at offset 40, not 44.
> |    Instead of using an incorrect hardcoded offset, let the compiler
> |    figure it out for us with offsetof().
> |
> |    Differential Revision: https://reviews.freebsd.org/D1543
> 
> It's not completely clear to me why we did not encounter this before;
> a comment before the erroneous write states:
> 
> /*
> * update the offset of section header table in elf
> * header if needed.
> */
> 
> so I presume something about the object file created by gcc 4.9 causes
> this code to be executed, while builds using the in-tree compiler did
> not.

Ah Yes! I remember now! We should find the FreeBSD version at that date
and either build it when we’re cross compiling, or rebuild it when we’re
bootstrapping.

Thanks for finding this Ed.

Warner

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