meson: support building without libc

Introduce a new meson option 'nolibc'.
Include the headers in src/arch when building liburing.
Build the src/syscall.c as seperate library for the tests when building
without libc.

Signed-off-by: Florian Fischer <[email protected]>

Author: fischerling

meson.build

@@ -72,6 +72,10 @@ has_cxx = true
 has_ucontext = (cc.has_type('ucontext_t', prefix: '#include <ucontext.h>')
   and cc.has_function('makecontext', prefix: '#include <ucontext.h>'))
 
+nolibc = get_option('nolibc')
+
+build_tests = get_option('tests')
+
 conf_data = configuration_data()
 conf_data.set('CONFIG_HAVE_KERNEL_RWF_T', has__kernel_rwf_t)
 conf_data.set('CONFIG_HAVE_KERNEL_TIMESPEC', has__kernel_timespec)
@@ -80,6 +84,8 @@ conf_data.set('CONFIG_HAVE_STATX', has_statx)
 conf_data.set('CONFIG_HAVE_GLIBC_STATX', glibc_statx)
 conf_data.set('CONFIG_HAVE_CXX', has_cxx)
 conf_data.set('CONFIG_HAVE_UCONTEXT', has_ucontext)
+conf_data.set('CONFIG_NOLIBC', nolibc)
+conf_data.set('LIBURING_BUILD_TEST', build_tests)
 configure_file(output: 'config-host.h',
                configuration: conf_data)
 
@@ -90,7 +96,7 @@ if get_option('examples')
     subdir('examples')
 endif
 
-if get_option('tests')
+if build_tests
     if get_option('default_library') != 'both'
         error('default_library=both required to build tests')
     endif

meson_options.txt

@@ -7,3 +7,8 @@ option('tests',
        type : 'boolean',
        value : false,
        description : 'Build test programs')
+
+option('nolibc',
+       type : 'boolean',
+       value : false,
+       description : 'Build liburing without libc')

src/meson.build

@@ -1,18 +1,30 @@
 subdir('include')
 
-inc = include_directories(['include'])
+liburing_includes = include_directories(['include'])
+liburing_internal_includes = [liburing_includes]
+
+liburing_sources = ['queue.c', 'register.c', 'setup.c']
+liburing_c_args = ['-DLIBURING_INTERNAL', '-fno-stack-protector']
+liburing_link_args = ['-Wl,--version-script=' + meson.current_source_dir() + '/liburing.map']
+
+if nolibc
+  liburing_internal_includes += include_directories(['arch'])
+
+  liburing_sources += ['nolibc.c']
+  liburing_c_args += ['-nostdlib', '-nodefaultlibs', '-ffreestanding']
+  liburing_link_args += ['-nostdlib', '-nodefaultlibs']
+else
+  liburing_sources += ['syscall.c']
+endif
 
 liburing = library('uring',
-                   'queue.c',
-                   'register.c',
-                   'setup.c',
-                   'syscall.c',
-                   include_directories: inc,
-                   c_args: ['-DLIBURING_INTERNAL', '-fno-stack-protector'],
-                   link_args: '-Wl,--version-script=' + meson.current_source_dir() + '/liburing.map',
+                   liburing_sources,
+                   include_directories: liburing_internal_includes,
+                   c_args: liburing_c_args,
+                   link_args: liburing_link_args,
                    link_depends: 'liburing.map',
                    version: meson.project_version(),
                    install: true)
 
 uring = declare_dependency(link_with: liburing,
-                           include_directories: inc)
+                           include_directories: liburing_includes)

test/meson.build

@@ -159,6 +159,16 @@ endif
 
 test_dependencies = [thread_dep]
 
+if nolibc
+  syscall_lib = static_library('syscall',
+                        '../src/syscall.c',
+                        include_directories: liburing_includes)
+
+  syscall_dep = declare_dependency(link_with: syscall_lib,
+                                   include_directories: liburing_includes)
+  test_dependencies += [syscall_dep]
+endif
+
 foreach test_source: all_tests
     # Tests are not allowed to contain multiple '.' in their name
     # using the meson filesystem module would solve this restriction
@@ -168,7 +178,7 @@ foreach test_source: all_tests
                [test_source, 'helpers.c'],
                c_args: xcflags,
                cpp_args: xcflags,
-               include_directories: inc,
+               include_directories: liburing_internal_includes,
                link_with: liburing.get_static_lib(),
                dependencies: test_dependencies,
                install: true,