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

[Jan Beulich]

On 20.06.2024 12:13, Nick Clifton wrote:
> 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 ?

Lgtm, fwiw.

Jan