[swift-dev] Porting swift to FreeBSD

[Davide Italiano]

On Sun, Dec 13, 2015 at 12:30 AM, Dmitri Gribenko <gribozavr at gmail.com> wrote:
> On Sat, Dec 12, 2015 at 9:26 PM, Davide Italiano <dccitaliano at gmail.com> wrote:
>> On Sun, Dec 13, 2015 at 12:22 AM, Dmitri Gribenko <gribozavr at gmail.com> wrote:
>>> On Sat, Dec 12, 2015 at 9:09 PM, Davide Italiano <dccitaliano at gmail.com> wrote:
>>>> On Sat, Dec 12, 2015 at 11:45 PM, Dmitri Gribenko <gribozavr at gmail.com> wrote:
>>>>> On Sat, Dec 12, 2015 at 8:29 PM, Davide Italiano via swift-dev
>>>>> <swift-dev at swift.org> wrote:
>>>>>> Hi,
>>>>>> I'm a FreeBSD developer who has been working on porting swift to FreeBSD.
>>>>>> I'm at a point where with a local patch (
>>>>>> https://people.freebsd.org/~davide/swift/build_freebsd.diff ) to fix
>>>>>> build errors I'm able to build the compiler itself on FreeBSD 11
>>>>>> (-CURRENT).
>>>>>
>>>>> +Doug for this patch.
>>>>>
>>>>>> The compiler itself seems to work fine (at least semantic analysis is
>>>>>> able to produce the correct result for toy examples).
>>>>>> Example:
>>>>>>
>>>>>> % cat hello.swift
>>>>>> let number = 4
>>>>>> println(number)
>>>>>>
>>>>>> % ./swiftc hello.swift -o hello
>>>>>> hello.swift:2:1: error: 'println' has been renamed to 'print'
>>>>>> println(number)
>>>>>> ^~~~~~~
>>>>>> [...]
>>>>>>
>>>>>> The executables generated seem to have some problems, though.
>>>>>> This is what I see:
>>>>>>
>>>>>> % cat hello2.swift
>>>>>> let number = 4
>>>>>> print(number)
>>>>>> % ./swiftc hello2.swift -o hello2
>>>>>>  % ./hello2
>>>>>> Int(String(String(String(String(String(String(String(String(String(String(String(String(String(String(String(String(String(String(String(String(String(String(String(String(String(String(String(Stri
>>>>>
>>>>> The reason is that the program can't find the protocol conformance
>>>>> tables.  On Linux, we are using a linker script to collect all
>>>>> conformances into one section, and insert symbols at the beginning and
>>>>> at the end, see stdlib/public/runtime/swift.ld.  The code that reads
>>>>> these sections is in stdlib/public/runtime/Casting.cpp.
>>>>>
>>>>
>>>> Thanks Dmitri.
>>>> The linker script is actually executed on FreeBSD as well (with a
>>>> recent version of GNU ld, with the old ld shipped with FreeBSD or gold
>>>> the parsing of the linker script fails)
>>>>
>>>> and the section is created (as objdump -h witnesses):
>>>>
>>>>  20 .dtors        00000010  0000000000603218  0000000000603218  00003218  2**3
>>>>                   CONTENTS, ALLOC, LOAD, DATA
>>>>  21 .swift2_protocol_conformances 00000008  0000000000603228
>>>> 0000000000603228  00003228  2**0
>>>>                   CONTENTS, ALLOC, LOAD, DATA
>>>>  22 .jcr          00000008  0000000000603230  0000000000603230  00003230  2**3
>>>>                   CONTENTS, ALLOC, LOAD, DATA
>>>>
>>>> % objdump -t ./hello | grep conformances
>>>> 0000000000603228 l    d  .swift2_protocol_conformances
>>>> 0000000000000000              .swift2_protocol_conformances
>>>> 0000000000603228 g       .swift2_protocol_conformances
>>>> 0000000000000000              .swift2_protocol_conformances_start
>>>>
>>>> Although the section seems to be empty/corrupted:
>>>
>>> It should be empty in the binary (since this simple program does not
>>> define any new conformances to protocols).  Could you try checking the
>>> standard library, libswiftCore.so:
>>>
>>
>>  % objdump -t ./lib/swift/freebsd/x86_64/libswiftCore.so | grep conformances
>> 0000000000833710 l    d  .swift2_protocol_conformances
>> 0000000000000000              .swift2_protocol_conformances
>> 0000000000833710 l     O .swift2_protocol_conformances
>> 0000000000002eb0              l_protocol_conformances
>> 00000000008365c0 g       .swift2_protocol_conformances
>> 0000000000000000              _edata
>>
>>  % objdump -s -j .swift2_protocol_conformances
>> ./lib/swift/freebsd/libswiftCore.so |head -n 10
>>
>> ./lib/swift/freebsd/libswiftCore.so:     file format elf64-x86-64-freebsd
>>
>> Contents of section .swift2_protocol_conformances:
>>  833710 00000000 00000000 00000000 04000000  ................
>>  833720 00000000 00000000 00000000 04000000  ................
>
> The section should start with an 8-byte size of the conformances
> section, seems to be missing here (compare to my output, which has
> "b02e0000 00000000").
>
> The linker script adds this size using:
>
> QUAD(SIZEOF(.swift2_protocol_conformances) - 8) ;
>
> Could you verify you have that line?
>

hmm, apparently we replied almost at the same time.
Anyway, yes, my linker script has the QUAD line.

SECTIONS
{
  .swift2_protocol_conformances :
  {
    .swift2_protocol_conformances_start = . ;
    QUAD(SIZEOF(.swift2_protocol_conformances) - 8) ;
    *(.swift2_protocol_conformances) ;
  }
}
INSERT AFTER .dtors