I believe that the get_exec_file function is unnecessary, and the code
can be simplified if we remove it.
Consider for instance when you "run" a program on Linux with native
debugging.
1. run_command_1 obtains the executable file from
`current_program_space->exec_filename ()`
2. it passes it to `run_target->create_inferior()`, which is
`inf_ptrace_target::create_inferior()` in this case, which then
passes it to `fork_inferior()`
3. `fork_inferior()` then has a fallback, where if the passed exec file
is nullptr, it gets its from `get_exec_file()`.
4. `get_exec_file()` returns `current_program_space->exec_filename ()`
- just like the things we started with - or errors out if the
current program space doesn't have a specified executable.
If there's no exec filename passed in step 1, there's not going to be
any in step 4, so it seems pointless to call `get_exec_file()`, we could
just error out when `exec_file` is nullptr. But we can't error out
directly in `fork_inferior()`, since the error is GDB-specific, and that
function is shared with GDBserver.
Speaking of GDBserver, all code paths that lead to `fork_inferior()`
provide a non-nullptr exec file.
Therefore, to simplify things:
- Make `fork_inferior()` assume that the passed exec file is not
nullptr, don't call `get_exec_file()`
- Change some targets (darwin-nat, go32-nat, gnu-nat, inf-ptrace,
nto-procfs, procfs) to error out when the exec file passed to their
create_inferior method is nullptr. Some targets are fine with a
nullptr exec file, so we can't check that in `run_command_1()`.
- Add the `no_executable_specified_error()` function, which re-uses the
error message that `get_exec_file()` had.
- Change some targets (go32-nat, nto-procfs) to not call
`get_exec_file()`, since it's pointless for the same reason as in the
example above, if it returns, it's going the be the same value as the
`exec_file` parameter. Just rely on `exec_file`.
- Remove the final use of `get_exec_file()`, in `load_command()`.
- Remove the `get_exec_file()` implementations in GDB and GDBserver and
remove the shared declaration.
Change-Id: I601c16498e455f7baa1f111a179da2f6c913baa3
Approved-By: Tom Tromey <tom@tromey.com>
7831bc9185