RFC: PR 31761: Stop the linker from overwriting source files

[Nick Clifton]

Hi Guys,

 > Alan Modra wrote:
> I think your instincts about this PR as shown by your initial comments
> in the PR were correct.  I don't think ld should restrict the file
> name given on its command line in any way, except for sanity checking
> against other command line arguments.  Trying to make things foolproof
> always fails.

You know what - you are right.  It is a fool's game trying to stop people
from being fools.

Instead I think that the best thing to do would be to document the current
behaviour.  So attached is an alternative patch that updates the description
of the -o option.  With the patch applied the text now reads like this:

   '-o OUTPUT'
   '--output=OUTPUT'
      Use OUTPUT as the name for the program produced by 'ld'; if this
      option is not specified, the name 'a.out' is used by default.  The
      script command 'OUTPUT' can also specify the output file name.

      Note - the linker will delete the output file before it starts to
      write to it.  It will do this even if it turns out that the link
      cannot be completed due to errors.

      Note - the linker will check to make sure that the output file name
      does not match the name of any of the input files, but that is all.
      In particular it will not complain if the output file might
      overwrite a source file or some other important file.  Therefore in
      build systems it is recommended to use the '-o' option as the last
      option on the linker command line.  For example consider:

             ld -o $(EXE) $(OBJS)
             ld $(OBJS) -o $(EXE)

      If the 'EXE' variable is not defined for some reason, the first
      version of the linker command could end up deleting one of the
      object files (the first one in the 'OBJS' list) whereas the second
      version of the linker command will generate an error message and
      not delete anything.

   What do people think ?

Cheers
   Nick
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