stubs: include stubs only if needed

Currently it is not documented anywhere why some functions need to
be stubbed.

Group the files in stubs/meson.build according to who needs them, both
to reduce the size of the compilation and to clarify the use of stubs.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Message-ID: <20240408155330.522792-18-pbonzini@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

stubs/meson.build

@@ -1,58 +1,86 @@
-stub_ss.add(files('bdrv-next-monitor-owned.c'))
-stub_ss.add(files('blk-commit-all.c'))
-stub_ss.add(files('blk-exp-close-all.c'))
-stub_ss.add(files('blockdev-close-all-bdrv-states.c'))
-stub_ss.add(files('change-state-handler.c'))
-stub_ss.add(files('cmos.c'))
+# If possible, add new files to other directories, by using "if_false".
+# If you need them here, try to add them under one of the if statements
+# below, so that it is clear who needs the stubbed functionality.
+
 stub_ss.add(files('cpu-get-clock.c'))
-stub_ss.add(files('cpus-get-virtual-clock.c'))
-stub_ss.add(files('qemu-timer-notify-cb.c'))
-stub_ss.add(files('icount.c'))
-stub_ss.add(files('dump.c'))
-stub_ss.add(files('error-printf.c'))
 stub_ss.add(files('fdset.c'))
-stub_ss.add(files('gdbstub.c'))
-stub_ss.add(files('get-vm-name.c'))
-stub_ss.add(files('graph-lock.c'))
-stub_ss.add(files('hotplug-stubs.c'))
-if linux_io_uring.found()
-  stub_ss.add(files('io_uring.c'))
-endif
 stub_ss.add(files('iothread-lock.c'))
-if have_block
-  stub_ss.add(files('iothread-lock-block.c'))
-endif
 stub_ss.add(files('is-daemonized.c'))
-if libaio.found()
-  stub_ss.add(files('linux-aio.c'))
-endif
-stub_ss.add(files('migr-blocker.c'))
-stub_ss.add(files('monitor.c'))
 stub_ss.add(files('monitor-core.c'))
-stub_ss.add(files('physmem.c'))
-stub_ss.add(files('qemu-timer-notify-cb.c'))
-stub_ss.add(files('qmp-command-available.c'))
-stub_ss.add(files('qmp-quit.c'))
-stub_ss.add(files('qtest.c'))
-stub_ss.add(files('ram-block.c'))
-stub_ss.add(files('replay.c'))
 stub_ss.add(files('replay-mode.c'))
-stub_ss.add(files('runstate-check.c'))
-stub_ss.add(files('sysbus.c'))
-stub_ss.add(files('target-get-monitor-def.c'))
-stub_ss.add(files('target-monitor-defs.c'))
 stub_ss.add(files('trace-control.c'))
-stub_ss.add(files('uuid.c'))
-stub_ss.add(files('vmstate.c'))
-stub_ss.add(files('vm-stop.c'))
-stub_ss.add(files('win32-kbd-hook.c'))
-stub_ss.add(files('cpu-synchronize-state.c'))
-if have_block or have_ga
+
+if have_block
+  stub_ss.add(files('bdrv-next-monitor-owned.c'))
+  stub_ss.add(files('blk-commit-all.c'))
+  stub_ss.add(files('blk-exp-close-all.c'))
+  stub_ss.add(files('blockdev-close-all-bdrv-states.c'))
+  stub_ss.add(files('change-state-handler.c'))
+  stub_ss.add(files('get-vm-name.c'))
+  stub_ss.add(files('iothread-lock-block.c'))
+  stub_ss.add(files('migr-blocker.c'))
+  stub_ss.add(files('physmem.c'))
+  stub_ss.add(files('ram-block.c'))
   stub_ss.add(files('replay-tools.c'))
+  stub_ss.add(files('runstate-check.c'))
+  stub_ss.add(files('uuid.c'))
 endif
+
+if have_block or have_ga
+  # stubs for hooks in util/main-loop.c, util/async.c etc.
+  stub_ss.add(files('cpus-get-virtual-clock.c'))
+  stub_ss.add(files('icount.c'))
+  stub_ss.add(files('graph-lock.c'))
+  if linux_io_uring.found()
+    stub_ss.add(files('io_uring.c'))
+  endif
+  if libaio.found()
+    stub_ss.add(files('linux-aio.c'))
+  endif
+  stub_ss.add(files('qemu-timer-notify-cb.c'))
+
+  # stubs for monitor
+  stub_ss.add(files('monitor-internal.c'))
+  stub_ss.add(files('qmp-command-available.c'))
+  stub_ss.add(files('qmp-quit.c'))
+endif
+
+if have_block or have_user
+  stub_ss.add(files('qtest.c'))
+  stub_ss.add(files('vm-stop.c'))
+  stub_ss.add(files('vmstate.c'))
+
+  # more symbols provided by the monitor
+  stub_ss.add(files('error-printf.c'))
+endif
+
+if have_user
+  # Symbols that are used by hw/core.
+  stub_ss.add(files('cpu-synchronize-state.c'))
+  stub_ss.add(files('qdev.c'))
+endif
+
 if have_system
+  # Symbols that are only needed in some configurations.  Try not
+  # adding more of these.  If the symbol is used in specific_ss,
+  # in particular, consider defining a preprocessor macro via
+  # Kconfig or configs/targets/.
+  stub_ss.add(files('dump.c'))
+  stub_ss.add(files('cmos.c'))
   stub_ss.add(files('fw_cfg.c'))
+  stub_ss.add(files('target-get-monitor-def.c'))
+  stub_ss.add(files('target-monitor-defs.c'))
+  stub_ss.add(files('win32-kbd-hook.c'))
   stub_ss.add(files('xen-hw-stub.c'))
-else
-  stub_ss.add(files('qdev.c'))
+endif
+
+if have_system or have_user
+  stub_ss.add(files('gdbstub.c'))
+
+  # Also included in have_system for --disable-tcg builds
+  stub_ss.add(files('replay.c'))
+
+  # Also included in have_system for tests/unit/test-qdev-global-props
+  stub_ss.add(files('hotplug-stubs.c'))
+  stub_ss.add(files('sysbus.c'))
 endif