[Bug ld/28619] New: -m option is not ignored when is immediately preceded by -o option

[egor_suvorov at mail dot ru]

https://sourceware.org/bugzilla/show_bug.cgi?id=28619

            Bug ID: 28619
           Summary: -m option is not ignored when is immediately preceded
                    by -o option
           Product: binutils
           Version: unspecified
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: ld
          Assignee: unassigned at sourceware dot org
          Reporter: egor_suvorov at mail dot ru
  Target Milestone: ---

Here are upstream bugs for GCC and Clang:
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103362
https://bugs.llvm.org/show_bug.cgi?id=52583
And the initial StackOverflow question:
https://stackoverflow.com/questions/70069809/unrecognized-emulation-mode-ain-when-compiling-with-gcc-on-ubuntu

Steps to reproduce:

1. Take an arbitrary small C program, compile it to an object file e.g. `a.o`.
I've used the following incorrect one compiled with `gcc main.c -c`:

`void _start(){}

2. `ld main.o -o -main` - note that the dash before `main` is not a typo.

Expected result: linking is successful, output is written to a file name
`-main`.

Real result:

ld: unrecognised emulation mode: ain
Supported emulations: elf_x86_64 elf32_x86_64 elf_i386 elf_iamcu elf_l1om
elf_k1om i386pep i386pe

Extra details:

It seems to me that the `-main` command line argument is parsed twice: once as
an argument for the `-o` option, and once as a `-m` flag.

For example, if I run `ld main.o -o -melf_x86_64`, linking succeeds and output
is written to `./-melf_x86_64`.

If I try `ld main.o -o -mi386` it fails with the following message:

ld: i386:x86-64 architecture of input file `main.o' is incompatible with i386
output

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