ui_file_rewind is a ui_file method that only really works with mem
buffer files, and is a nop on other ui_file types. It'd be desirable
to eliminate it from the base ui_file interface, and move it to the
"mem_fileopen" subclass of ui_file instead. A following patch does
just that.
Unfortunately, there are a couple references to ui_file_rewind inside
gdb_disassembler::pretty_print_insn that were made harder to eliminate
with the recent addition of the gdb_disassembler wrapper.
Before the gdb_disassembler wrapper was added, in commit
e47ad6c0bd7aa3 ("Refactor disassembly code"), gdb_pretty_print_insn
used to be passed a ui_file pointer as argument, and it was simple to
adjust that pointer be a "mem_fileopen" ui_file pointer instead, since
there's only one gdb_pretty_print_insn caller.
That commit made gdb_pretty_print_insn be a method of
gdb_disassembler, and removed the method's ui_file parameter at the
same time, replaced by referencing the gdb_disassembler's stream
instead. The trouble is that a gdb_disassembler can be instantiated
with a pointer any kind of ui_file. Casting the gdb_disassembler's
stream to a mem_fileopen ui_file inside
gdb_disassembler::pretty_print_insn in order to call the reset method
would be gross hack.
The fix here is to:
- make gdb_disassembler::pretty_print_insn a be free function again
instead of a method of gdb_disassembler. I.e., bring back
gdb_pretty_print_insn.
- but, don't add back the ui_file * parameter. We'd always be
passing in a fresh mem_fileopen anyway, so move the mem_fileopen
allocation inside. That is a better interface, given that the
ui_file is only ever used as temporary scratch buffer as an
implementation detail of gdb_pretty_print_insn. The function's
real "where to send output" parameter is the ui_out pointer.
- don't add back a disassemble_info pointer either. That used to be
necessary for this bit:
err = m_di.read_memory_func (pc, &data, 1, &m_di);
if (err != 0)
m_di.memory_error_func (err, pc, &m_di);
... but AFAIK, it's not really necessary. We can replace those
three lines with a call to read_code. This seems to fix a
regression even, because before commit d8b49cf0c891d0 ("Don't throw
exception in dis_asm_memory_error"), that memory_error_func call
would throw an error/exception, but now it only records the error
in the gdb_disassembler's m_err_memaddr field. (read_code throws
on error.)
With all these, gdb_pretty_print_insn is completely layered on top of
gdb_disassembler only using the latter's public API.