Re: MIPS ECOFF ld --embedded-relocs: looks like a bug

[Ian Lance Taylor <ian at zembu dot com>]

   Date: Wed, 7 Jun 00 16:07:36 CDT
   From: msokolov@ivan.Harhan.ORG (Michael Sokolov)

   I'm looking at the MIPS ECOFF ld --embedded-relocs code with an eye toward
   porting it to m68k (COFF and ELF), and I see what seems to be a bug. This code
   was written by Ian, so I hope he still reads this list and will comment on
   this. :-) In ld/emultempl/mipsecoff.em, after having created the .rel.sdata
   section to hold the embedded relocs in gld{EMULATION_NAME}_after_open, it fills
   it in gld{EMULATION_NAME}_after_allocation by calling ecoff-mips BFD backend
   function bfd_mips_ecoff_create_embedded_relocs for each input BFD. Here is my
   question. What if an input BFD is not ecoff-mips? What if I configure and build
   a mips-ecoff toolchain with a libbfd.a that has all targets in it and run
   mips-ecoff-ld --embedded-relocs -o myexec myobj.o, where myobj.o is an ELF
   object? From what I see, bfd_mips_ecoff_create_embedded_relocs in the ecoff-
   mips backend will be called with an elf32-mips BFD. Wouldn't this core dump or
   something like that?

Yes, this looks like a bug.

   It seems to me that one must first check the BFD target before directly calling
   a backend function in this fashion. What should we do if the BFD target isn't
   what we expect?

Unless you write some fairly hairy code, you just give a fatal error
message.

   I don't know MIPS, so I can't judge the intent of the
   --embedded-relocs code and the fitness of the implementation for its purpose,
   but the comments say that ld --embedded-relocs is legal only for objects
   assembled with GNU as -membedded-pic. Looking at gas/config/tc-mips.c, I see
   that GNU as appears to support -membedded-pic equally well for ECOFF and ELF.
   Thus it seems to me that bfd_mips_ecoff_create_embedded_relocs should be ported
   to the elf32-mips backend as well. What should we do in ld until then? Give a
   "sorry, not supported yet" error message when trying to link in an ELF object?

Yes.

Ian