Re: gold linker 2.22 regressed for DragonFly

[Ian Lance Taylor <iant at google dot com>]

John Marino <binutils@marino.st> writes:

> When binutils 2.21 was imported into DragonFly, gold could successful
> link world and kernel, but not the kernel modules.  When binutils 2.22
> was imported, gold can no longer even link itself.
>
> After executing "gmake check-TESTS", the new version of gold linked by
> gold segfaults immediately.  The General_Options->format() method
> returns null, crashing string_to_object_format in options.cc.  I'm not
> very strong in C++, so I'm having trouble figuring out why format() is
> not getting defined, or what has changed between gold 2.21 and gold
> 2.22.
>
> The backtrace is attached.  I'm sure somebody here should be able to
> point me to code that should be modified to support DragonFly BSD.
>
> Thanks,
> John
>
> The program being debugged has been started already.
> Start it from the beginning? (y or n) 
> Starting program: /home/marino/workzone/test-222/gold/ld1 
>
> Program received signal SIGSEGV, Segmentation fault.
> 0x000000000052e534 in gold::General_options::string_to_object_format (arg=0x0)
>     at ../../binutils-2.22/gold/options.cc:655
> 655	  if (strncmp(arg, "elf", 3) == 0)
> #0  0x000000000052e534 in gold::General_options::string_to_object_format (
>     arg=0x0) at ../../binutils-2.22/gold/options.cc:655

string_to_object_format is being called with a NULL pointer.

> #1  0x000000000053b5e2 in format_enum (this=0x62a5fe)
>     at ../../binutils-2.22/gold/options.cc:937

This line is
  return General_options::string_to_object_format(this->format());
so this->format() is return a NULL string.

That should not happen.  this->format() is going to return the value of
this->format_.value.  That should be initialized to "elf" and nothing
should ever change it to NULL.  In this case "this" appears to refer to
the static variable Position_dependent_options::default_options_.

I'm not aware of anything that has changed in this area between binutils
2.21 and 2.22.  The same code is in 2.21.

I guess I would debug it by verifying that
Position_independent_options::default_options_.format_.value is in fact
initialized to "elf".  If not, why not?  If it is, when does it change?

Ian