[PATCH][ARM]Use different startfile and endfile for elf target when generating shared object.

[Renlin Li]

Hi Kugan,

some of the targets do include pie, and use the same crtbegin file as shared object.
For example, alpha/elf.h

And there are targets which don't do that,
For example, sh/elf.h

Most of the elf target seem only consider the simple case.

The purpose of this patch is to make it possible to correctly check whether current 
toolchain supports shared object.

Current dejegnu target selector "shared" tries to compile a simple source code to with 
"-shared -fpic" options to check whether "-shared" is supported.

For arm baremetal targets with, this is not sufficient.

arm-none-eabi is built with multilib. When running this testcase, if it's
compiled with "-march=armv7-a".
The crtbegin.o for this architecture version contains relocations which
cannot be used in shared object.
This test will fail.

if no cpu or architecture is specified, the default cpu will be arm7tdmi.
The test will pass as crtbegin.o for this version doesn't contains any relocations
only allowed in shared object.

To make this "shared" target selector work for arm baremetal toolchain. The correct way is 
to use different startup file for shared and non-shared toolchain.

If the toolchain doesn't support "-shared" option, and someone attempts to use it
to create shared object, it will complaint that "crtbeginS.o" cannot not be found.

A full history of discussion is here:
https://gcc.gnu.org/ml/gcc-patches/2016-03/msg00322.html


Regards,
Renlin


On 12/01/17 11:47, kugan wrote:
> Hi,
>
> On 16/06/16 21:04, Renlin Li wrote:
>>  /* Now we define the strings used to build the spec file.  */
>> -#define UNKNOWN_ELF_STARTFILE_SPEC    " crti%O%s crtbegin%O%s crt0%O%s"
>> +#define UNKNOWN_ELF_STARTFILE_SPEC    \
>> +  "crti%O%s \
>> +  %{!shared:crtbegin%O%s} %{shared:crtbeginS%O%s} \
>> +  crt0%O%s"
>
> Some targets seems to use shared|pie. When you change it, shouldn't it also include for pie?
>
> Thanks,
> Kugan