[PATCH 04/10] meson: option to build as shared library

[Joelle van Dyne]

From: osy <osy86@users.noreply.github.com>

On iOS, we cannot fork() new processes, so the best way to load QEMU into an
app is through a shared library. We add a new configure option
`--enable-shared-lib` that will build the bulk of QEMU into a shared lib.
The usual executables will then link to the library.

Signed-off-by: Joelle van Dyne <j@getutm.app>
---
 configure         | 14 ++++++++++++--
 meson.build       | 40 ++++++++++++++++++++++++++++++++++------
 meson_options.txt |  2 ++
 3 files changed, 48 insertions(+), 8 deletions(-)

diff --git a/configure b/configure
index c474d7c221..37b27d9e35 100755
--- a/configure
+++ b/configure
@@ -448,6 +448,7 @@ ninja=""
 skip_meson=no
 gettext=""
 host_block_device_support="yes"
+shared_lib="false"
 
 bogus_os="no"
 malloc_trim="auto"
@@ -1563,6 +1564,10 @@ for opt do
   ;;
   --disable-libdaxctl) libdaxctl=no
   ;;
+  --enable-shared-lib) shared_lib=true
+  ;;
+  --disable-shared-lib) shared_lib=false
+  ;;
   *)
       echo "ERROR: unknown option $opt"
       echo "Try '$0 --help' for more information"
@@ -1770,6 +1775,7 @@ Advanced options (experts only):
                            enable plugins via shared library loading
   --disable-containers     don't use containers for cross-building
   --gdb=GDB-path           gdb to use for gdbstub tests [$gdb_bin]
+  --enable-shared-lib      build QEMU as a shared library
 
 Optional features, enabled with --enable-FEATURE and
 disabled with --disable-FEATURE, default is enabled if available:
@@ -7211,7 +7217,11 @@ echo "ranlib = [$(meson_quote $ranlib)]" >> $cross
 if has $sdl2_config; then
   echo "sdl2-config = [$(meson_quote $sdl2_config)]" >> $cross
 fi
-echo "strip = [$(meson_quote $strip)]" >> $cross
+if test "$shared_lib" = "true"; then
+  echo "strip = [$(meson_quote $strip), '-x']" >> $cross
+else
+  echo "strip = [$(meson_quote $strip)]" >> $cross
+fi
 echo "windres = [$(meson_quote $windres)]" >> $cross
 if test "$cross_compile" = "yes"; then
     cross_arg="--cross-file config-meson.cross"
@@ -7273,7 +7283,7 @@ NINJA=${ninja:-$PWD/ninjatool} $meson setup \
        -Dcocoa=$cocoa -Dmpath=$mpath -Dsdl=$sdl -Dsdl_image=$sdl_image \
        -Dvnc=$vnc -Dvnc_sasl=$vnc_sasl -Dvnc_jpeg=$vnc_jpeg -Dvnc_png=$vnc_png 
\
        -Dgettext=$gettext -Dxkbcommon=$xkbcommon -Du2f=$u2f \
-       -Dcapstone=$capstone -Dslirp=$slirp -Dfdt=$fdt \
+       -Dcapstone=$capstone -Dslirp=$slirp -Dfdt=$fdt -Dshared-lib=$shared_lib 
\
         $cross_arg \
         "$PWD" "$source_path"
 
diff --git a/meson.build b/meson.build
index 69a3c00cce..32cf08619f 100644
--- a/meson.build
+++ b/meson.build
@@ -1565,14 +1565,31 @@ foreach target : target_dirs
   arch_srcs += target_specific.sources()
   arch_deps += target_specific.dependencies()
 
-  lib = static_library('qemu-' + target,
+  if get_option('shared-lib')
+    build_lib_args = {
+      'target_type': 'shared_library',
+      'install': true,
+      'dependencies': arch_deps + deps,
+      'link_language': link_language,
+      'link_depends': [block_syms, qemu_syms],
+      'link_args': link_args + 
cc.get_supported_link_arguments(['-Wl,-U,_qemu_main'])
+    }
+  else
+    build_lib_args = {
+      'target_type': 'static_library',
+      'install': false,
+      'dependencies': arch_deps,
+      'name_suffix': 'fa'
+    }
+  endif
+
+  lib = build_target('qemu-' + target,
                  sources: arch_srcs + genh,
-                 dependencies: arch_deps,
                  objects: objects,
                  include_directories: target_inc,
                  c_args: c_args,
                  build_by_default: false,
-                 name_suffix: 'fa')
+                 kwargs: build_lib_args)
 
   if target.endswith('-softmmu')
     execs = [{
@@ -1606,17 +1623,27 @@ foreach target : target_dirs
       'dependencies': []
     }]
   endif
+  if get_option('shared-lib')
+    build_exe_args = {
+      'link_with': lib,
+      'link_args': link_args + 
cc.get_supported_link_arguments(['-Wl,--exclude-libs,ALL'])
+    }
+  else
+    build_exe_args = {
+      'objects': lib.extract_all_objects(recursive: true),
+      'link_args': link_args
+    }
+  endif
   foreach exe: execs
     emulators += {exe['name']:
          executable(exe['name'], exe['sources'],
                install: true,
                c_args: c_args,
                dependencies: arch_deps + deps + exe['dependencies'],
-               objects: lib.extract_all_objects(recursive: true),
                link_language: link_language,
                link_depends: [block_syms, qemu_syms] + exe.get('link_depends', 
[]),
-               link_args: link_args,
-               gui_app: exe['gui'])
+               gui_app: exe['gui'],
+               kwargs: build_exe_args)
     }
 
     if 'CONFIG_TRACE_SYSTEMTAP' in config_host
@@ -1758,6 +1785,7 @@ endif
 summary_info += {'Doc directory':     get_option('docdir')}
 summary_info += {'Build directory':   meson.current_build_dir()}
 summary_info += {'Source path':       meson.current_source_dir()}
+summary_info += {'build shared lib':  get_option('shared-lib')}
 summary_info += {'GIT binary':        config_host['GIT']}
 summary_info += {'GIT submodules':    config_host['GIT_SUBMODULES']}
 summary_info += {'C compiler':        meson.get_compiler('c').cmd_array()[0]}
diff --git a/meson_options.txt b/meson_options.txt
index 1d3c94840a..bcecbd5e12 100644
--- a/meson_options.txt
+++ b/meson_options.txt
@@ -2,6 +2,8 @@ option('qemu_suffix', type : 'string', value: 'qemu',
        description: 'Suffix for QEMU data/modules/config directories (can be 
empty)')
 option('docdir', type : 'string', value : 'doc',
        description: 'Base directory for documentation installation (can be 
empty)')
+option('shared-lib', type : 'boolean', value : false,
+       description: 'build QEMU as a shared library')
 
 option('gettext', type : 'boolean', value : true,
        description: 'Localization of the GTK+ user interface')
-- 
2.24.3 (Apple Git-128)