[RFA] Fix gdbserver build failure on arm-android.

  Hello,

The following patch...

| proc-service, extern "C"
|
| libthread_db.so calls symbols in the client (GDB), through the
| proc-service interface.  These routines must have extern "C" linkage
| so their symbol names are not mangled when GDB is built as a C++
| program.  On the GDBserver side, we were missing fallback declarations for
| all these symbols.
|
| gdb/ChangeLog:
|
|     * gdb_proc_service.h: Wrap with EXTERN_C_PUSH/EXTERN_C_POP.
|
| gdb/gdbserver/ChangeLog:
| 2015-02-27  Pedro Alves  <palves@redhat.com>
|
|     * gdb_proc_service.h: Wrap with EXTERN_C_PUSH/EXTERN_C_POP.
|     [!HAVE_PROC_SERVICE_H] (struct ps_prochandle): Forward declare.
|     [!HAVE_PROC_SERVICE_H] (ps_pdread, ps_pdwrite, ps_ptread)
|     ps_ptwrite, ps_lgetregs, ps_lsetregs, ps_lgetfpregs)
|     (ps_lsetfpregs, ps_getpid)
|     (ps_get_thread_area, ps_pglobal_lookup, ps_pstop, ps_pcontinue)
|     (ps_lstop, ps_lcontinue, ps_lgetxregsize, ps_lgetxregs)
|     (ps_lsetxregs, ps_plog): Declare.

... added a number of declarations which do not compile when cross-
compiling GDBserver on arm-android. The problem comes from type
prfpregset_t not being declared:

    /[...]/gdbserver/gdb_proc_service.h:98:47:
    error: unknown type name 'prfpregset_t'

After searching through the includes of the install we have,
I could not find that type being declared anywhere. So I did
the same as for prgregset_t, and created the typedef if the
type isn't declared.

gdb/gdbserver/ChangeLog:

        * configure.ac: Add prfpregset_t BFD_HAVE_SYS_PROCFS_TYPE check.
        * configure, config.in: Regenerate.
        * gdb_proc_service.h [HAVE_PRFPREGSET_T] (prfpregset_t):
        Declare typedef.

OK to commit?

Thanks,
  

On 05/08/2015 05:01 PM, Joel Brobecker wrote:
> Hello,
> 
> The following patch...
> 
> | proc-service, extern "C"
> |
> | libthread_db.so calls symbols in the client (GDB), through the
> | proc-service interface.  These routines must have extern "C" linkage
> | so their symbol names are not mangled when GDB is built as a C++
> | program.  On the GDBserver side, we were missing fallback declarations for
> | all these symbols.
> |
> | gdb/ChangeLog:
> |
> |     * gdb_proc_service.h: Wrap with EXTERN_C_PUSH/EXTERN_C_POP.
> |
> | gdb/gdbserver/ChangeLog:
> | 2015-02-27  Pedro Alves  <palves@redhat.com>
> |
> |     * gdb_proc_service.h: Wrap with EXTERN_C_PUSH/EXTERN_C_POP.
> |     [!HAVE_PROC_SERVICE_H] (struct ps_prochandle): Forward declare.
> |     [!HAVE_PROC_SERVICE_H] (ps_pdread, ps_pdwrite, ps_ptread)
> |     ps_ptwrite, ps_lgetregs, ps_lsetregs, ps_lgetfpregs)
> |     (ps_lsetfpregs, ps_getpid)
> |     (ps_get_thread_area, ps_pglobal_lookup, ps_pstop, ps_pcontinue)
> |     (ps_lstop, ps_lcontinue, ps_lgetxregsize, ps_lgetxregs)
> |     (ps_lsetxregs, ps_plog): Declare.
> 
> ... added a number of declarations which do not compile when cross-
> compiling GDBserver on arm-android. The problem comes from type
> prfpregset_t not being declared:
> 
>     /[...]/gdbserver/gdb_proc_service.h:98:47:
>     error: unknown type name 'prfpregset_t'
> 
> After searching through the includes of the install we have,
> I could not find that type being declared anywhere. So I did
> the same as for prgregset_t, and created the typedef if the
> type isn't declared.
> 
> gdb/gdbserver/ChangeLog:
> 
>         * configure.ac: Add prfpregset_t BFD_HAVE_SYS_PROCFS_TYPE check.
>         * configure, config.in: Regenerate.
>         * gdb_proc_service.h [HAVE_PRFPREGSET_T] (prfpregset_t):
>         Declare typedef.
> 
> OK to commit?

OK.

BTW, do you also trip on this one? :

 https://sourceware.org/ml/gdb/2015-04/msg00025.html

Thanks,
Pedro Alves
  

> > gdb/gdbserver/ChangeLog:
> > 
> >         * configure.ac: Add prfpregset_t BFD_HAVE_SYS_PROCFS_TYPE check.
> >         * configure, config.in: Regenerate.
> >         * gdb_proc_service.h [HAVE_PRFPREGSET_T] (prfpregset_t):
> >         Declare typedef.
> > 
> > OK to commit?
> 
> OK.

Thanks! Pushed to master.

> BTW, do you also trip on this one? :
> 
>  https://sourceware.org/ml/gdb/2015-04/msg00025.html

We don't, at the moment. But we're planning on upgrading to a newer
version in the next few weeks, so we might eventually hit that issue
too. We don't know yet which version we'll target, so I can't say
much more at the moment.
  

On 05/14/2015 03:17 PM, Joel Brobecker wrote:

>> BTW, do you also trip on this one? :
>>
>>  https://sourceware.org/ml/gdb/2015-04/msg00025.html
> 
> We don't, at the moment. But we're planning on upgrading to a newer
> version in the next few weeks, so we might eventually hit that issue
> too. We don't know yet which version we'll target, so I can't say
> much more at the moment.

OK.  Seems the clash is with the group_from_gid / user_from_uid
BSD functions that do a similar thing from what our
versions do.  E.g.,:

 http://nixdoc.net/man-pages/openbsd/man3/group_from_gid.3.html
 https://developer.apple.com/library/ios/documentation/System/Conceptual/ManPages_iPhoneOS/man3/group_from_gid.3.html

"functions first appeared in 4.4BSD".

Though BSD's return a pointer to a statically allocated
buffer, while gdb's take a buffer pointer as argument.

As glibc doesn't support those BSD functions, we don't trip
on that on GNU/Linux.

I think we should just rename our symbols.  E.g.,
 group_from_gid -> gdb_group_from_gid
 user_from_uid -> gdb_user_from_uid

Thanks,
Pedro Alves