meson.build: define stubs library per target base architecture

QEMU stubs (from stubs folder) have a unique feature: they emulate weak
symbols. Weak symbols are not supported on Windows with gcc. This is
achieved by defining a static library, so the linker can pick a file
only when one of its symbol is needed.

The problem is that common stubs are embedded in qemuutil, which is
defined and created before any target code. Thus, to benefit from the
same feature for target code, we need to create stub static libraries
for each target architecture.

To keep things simple, we declare one library per target base
architecture. This implies that stubs are compiled only once, and we
choose them to be system common files. This is not a big issue, since
stubs definition have no specific behaviour, out of returning a default
value, or stopping execution, which makes this safe to link them in user
binaries also.

Signed-off-by: Pierrick Bouvier <pierrick.bouvier@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Message-Id: <20260424230103.1579600-2-pierrick.bouvier@oss.qualcomm.com>
Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>

diff --git a/meson.build b/meson.build
index 987f33bacee7c2adae7f2bf6c94beabb3f45b0bb..5fbdc75a0fc0e16962a529fc32ee6986cfb0a508 100644 (file)
--- a/meson.build
+++ b/meson.build
@@ -3738,6 +3738,7 @@ target_user_arch = {}
 hw_common_arch = {}
 target_common_arch = {}
 target_common_system_arch = {}
+target_stubs_arch = {}
 
 # NOTE: the trace/ subdirectory needs the qapi_trace_events variable
 # that is filled in by qapi/.
@@ -4143,6 +4144,7 @@ common_all = static_library('common',
 # construct common libraries per base architecture
 target_common_arch_libs = {}
 target_common_system_arch_libs = {}
+target_stubs_arch_libs = {}
 foreach target_base_arch, config_base_arch : config_base_arch_mak
   target_inc = [include_directories('target' / target_base_arch)]
   inc = [common_user_inc + target_inc]
@@ -4202,6 +4204,15 @@ foreach target_base_arch, config_base_arch : config_base_arch_mak
       dependencies: src.all_dependencies() + common_deps + system_deps)
     target_common_system_arch_libs += {target_base_arch: lib}
   endif
+
+  if target_base_arch in target_stubs_arch
+    src = target_stubs_arch[target_base_arch]
+    lib = static_library('stubs_' + target_base_arch,
+                         sources: src.all_sources() + genh,
+                         include_directories: inc,
+                         c_args: target_system_c_args)
+    target_stubs_arch_libs += {target_base_arch: lib}
+  endif
 endforeach
 
 if have_rust
@@ -4363,6 +4374,11 @@ foreach target : target_dirs
     objects += lib.extract_objects(src.sources())
     arch_deps += src.dependencies()
   endif
+  lib_target_stubs = []
+  if target_base_arch in target_stubs_arch_libs
+    lib_target_stubs = [target_stubs_arch_libs[target_base_arch]]
+  endif
+  target_stubs = declare_dependency(link_with: lib_target_stubs)
 
   target_specific = specific_ss.apply(config_target, strict: false)
   arch_srcs += target_specific.sources()
@@ -4408,14 +4424,14 @@ foreach target : target_dirs
       'name': 'qemu-system-' + target_name,
       'win_subsystem': 'console',
       'sources': [main_rs, files('system/main.c')],
-      'dependencies': [sdl]
+      'dependencies': [sdl, target_stubs],
     }]
     if host_os == 'windows' and (sdl.found() or gtk.found())
       execs += [{
         'name': 'qemu-system-' + target_name + 'w',
         'win_subsystem': 'windows',
         'sources': [main_rs, files('system/main.c')],
-        'dependencies': [sdl]
+        'dependencies': [sdl, target_stubs],
       }]
     endif
     if get_option('fuzzing')
@@ -4432,7 +4448,7 @@ foreach target : target_dirs
       'name': 'qemu-' + target_name,
       'win_subsystem': 'console',
       'sources': [],
-      'dependencies': []
+      'dependencies': [target_stubs]
     }]
   endif
   foreach exe: execs