[Bug lto/51916] FAIL: gcc.dg/lto/trans-mem-3 c_lto_trans-mem-3_0.o-c_lto_trans-mem-3_1.o link, -flto (internal compiler error)

[iains at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51916

Iain Sandoe <iains at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2012-01-21
     Ever Confirmed|0                           |1

--- Comment #8 from Iain Sandoe <iains at gcc dot gnu.org> 2012-01-21 10:04:58 UTC ---
(In reply to comment #7)

Thanks for the debugging Patrick.

> Tracing a bit more, I see that simple_object_mach_o_match() ends with this:
> *errmsg = "Mach-O file found but no segment name specified";
> Indeed, lto-wrapper always gives NULL for the segment name.
> sobj = simple_object_start_read (fd, file_offset, NULL, &errmsg, &err);
> 
> So, since there is no documentation/specification of the
> simple_object_start_read function I cannot say if it is a gcc/lto bug or a
> libiberty bug.

include/simple_object.h:

/* Create an simple_object_read given DESCRIPTOR, an open file
   descriptor, and OFFSET, an offset within the file.  The offset is
   for use with archives, and should be 0 for an ordinary object file.
   The descriptor must remain open until done with the returned
   simple_object_read.  SEGMENT_NAME is used on Mach-O and is required
   on that platform: it means to only look at sections within the
   segment with that name.  It is ignored for other object file
   formats.  On error, this function returns NULL, and sets *ERRMSG to
   an error string and sets *ERR to an errno value or 0 if there is no
   relevant errno.  */

extern simple_object_read *
simple_object_start_read (int descriptor, off_t offset,
                          const char *segment_name, const char **errmsg,
                          int *err);

> Finally, there is a problem with lto-wrapper.c
>       if (!simple_object_find_section (sobj, LTO_SECTION_NAME_PREFIX "."
> "opts",
>                        &offset, &length, &errmsg, &err))
> In MacOSX, I don't know the section name for opts (I have __wrapper_index,
> __wrapper_sects, and __wrapper_names) but if I add the segment name "__GNU_LTO"
> , the section name is ".gnu.lto_.opts" (not existing in my files).

the sections are there (inside the wrapper - if you objdump or hexdump -C the
objects you'll see them) and if I apply this hack the link works (the objects
are correctly formed as of now):

Index: gcc/lto-wrapper.c
===================================================================
--- gcc/lto-wrapper.c   (revision 183359)
+++ gcc/lto-wrapper.c   (working copy)
@@ -479,7 +479,7 @@ run_gcc (unsigned argc, char *argv[])
       fd = open (argv[i], O_RDONLY);
       if (fd == -1)
        continue;
-      sobj = simple_object_start_read (fd, file_offset, NULL, &errmsg, &err);
+      sobj = simple_object_start_read (fd, file_offset, "__GNU_LTO", &errmsg,
&err);
       if (!sobj)
        {
          close (fd);


... so this is a build/config issue - or, alternatively, the segment name can
be specified as above since it is ignored for non-mach-o platforms.

thanks
Iain