New compiler function: cc.get_define()

Runs the pre-processor and fetches the value of the define.

Can find any arbitrary value and returns it as a string.

3 files changed, 72 insertions, 32 deletions

diff --git a/mesonbuild/compilers.py b/mesonbuild/compilers.py
index 7f3c82e..ce3f09a 100644
--- a/mesonbuild/compilers.py
+++ b/mesonbuild/compilers.py
@@ -906,8 +906,6 @@ class CCompiler(Compiler):
         return self.sanity_check_impl(work_dir, environment, 'sanitycheckc.c', code)
 
     def has_header(self, hname, prefix, env, extra_args=None, dependencies=None):
-        if extra_args is None:
-            extra_args = []
         fargs = {'prefix': prefix, 'header': hname}
         code = '''{prefix}
         #ifdef __has_include
@@ -921,8 +919,6 @@ class CCompiler(Compiler):
                              dependencies, 'preprocess')
 
     def has_header_symbol(self, hname, symbol, prefix, env, extra_args=None, dependencies=None):
-        if extra_args is None:
-            extra_args = []
         fargs = {'prefix': prefix, 'header': hname, 'symbol': symbol}
         t = '''{prefix}
         #include <{header}>
@@ -934,7 +930,7 @@ class CCompiler(Compiler):
         }}'''
         return self.compiles(t.format(**fargs), env, extra_args, dependencies)
 
-    def compiles(self, code, env, extra_args=None, dependencies=None, mode='compile'):
+    def _get_compiler_check_args(self, env, extra_args, dependencies, mode='compile'):
         if extra_args is None:
             extra_args = []
         elif isinstance(extra_args, str):
@@ -943,49 +939,41 @@ class CCompiler(Compiler):
             dependencies = []
         elif not isinstance(dependencies, list):
             dependencies = [dependencies]
-        # Add compile flags needed by dependencies
+        # Collect compiler arguments
         args = CompilerArgs(self)
         for d in dependencies:
+            # Add compile flags needed by dependencies
             args += d.get_compile_args()
+            if mode == 'link':
+                # Add link flags needed to find dependencies
+                args += d.get_link_args()
+        # Select a CRT if needed since we're linking
+        if mode == 'link':
+            args += self.get_linker_debug_crt_args()
         # Read c_args/cpp_args/etc from the cross-info file (if needed)
-        args += self.get_cross_extra_flags(env, compile=True, link=False)
+        args += self.get_cross_extra_flags(env, compile=(mode != 'preprocess'),
+                                           link=(mode == 'link'))
         # Add CFLAGS/CXXFLAGS/OBJCFLAGS/OBJCXXFLAGS from the env
         # We assume that the user has ensured these are compiler-specific
         args += env.coredata.external_args[self.language]
+        # Add LDFLAGS from the env. We assume that the user has ensured these
+        # are compiler-specific
+        if mode == 'link':
+            args += env.coredata.external_link_args[self.language]
         args += self.get_compiler_check_args()
         # extra_args must override all other arguments, so we add them last
         args += extra_args
+        return args
+
+    def compiles(self, code, env, extra_args=None, dependencies=None, mode='compile'):
+        args = self._get_compiler_check_args(env, extra_args, dependencies, mode)
         # We only want to compile; not link
         with self.compile(code, args.to_native(), mode) as p:
             return p.returncode == 0
 
     def _links_wrapper(self, code, env, extra_args, dependencies):
         "Shares common code between self.links and self.run"
-        if extra_args is None:
-            extra_args = []
-        elif isinstance(extra_args, str):
-            extra_args = [extra_args]
-        if dependencies is None:
-            dependencies = []
-        elif not isinstance(dependencies, list):
-            dependencies = [dependencies]
-        # Add compile and link flags needed by dependencies
-        args = CompilerArgs(self)
-        for d in dependencies:
-            args += d.get_compile_args()
-            args += d.get_link_args()
-        # Select a CRT if needed since we're linking
-        args += self.get_linker_debug_crt_args()
-        # Read c_args/c_link_args/cpp_args/cpp_link_args/etc from the
-        # cross-info file (if needed)
-        args += self.get_cross_extra_flags(env, compile=True, link=True)
-        # Add LDFLAGS from the env. We assume that the user has ensured these
-        # are compiler-specific
-        args += env.coredata.external_link_args[self.language]
-        # Add compiler check args such that they override
-        args += self.get_compiler_check_args()
-        # extra_args must override all other arguments, so we add them last
-        args += extra_args
+        args = self._get_compiler_check_args(env, extra_args, dependencies, mode='link')
         return self.compile(code, args.to_native())
 
     def links(self, code, env, extra_args=None, dependencies=None):
@@ -1141,6 +1129,24 @@ class CCompiler(Compiler):
             raise EnvironmentException('Could not determine alignment of %s. Sorry. You might want to file a bug.' % typename)
         return align
 
+    def get_define(self, dname, prefix, env, extra_args, dependencies):
+        delim = '"MESON_GET_DEFINE_DELIMITER"'
+        fargs = {'prefix': prefix, 'define': dname, 'delim': delim}
+        code = '''
+        #ifndef {define}
+        # define {define}
+        #endif
+        {prefix}
+        {delim}\n{define}'''
+        args = self._get_compiler_check_args(env, extra_args, dependencies,
+                                             mode='preprocess').to_native()
+        with self.compile(code.format(**fargs), args, 'preprocess') as p:
+            if p.returncode != 0:
+                raise EnvironmentException('Could not get define {!r}'.format(dname))
+        # Get the preprocessed value after the delimiter,
+        # minus the extra newline at the end
+        return p.stdo.split(delim + '\n')[-1][:-1]
+
     @staticmethod
     def _no_prototype_templ():
         """
diff --git a/mesonbuild/interpreter.py b/mesonbuild/interpreter.py
index 0c6d980..959ce6a 100644
--- a/mesonbuild/interpreter.py
+++ b/mesonbuild/interpreter.py
@@ -634,6 +634,7 @@ class CompilerHolder(InterpreterObject):
                              'get_id': self.get_id_method,
                              'compute_int': self.compute_int_method,
                              'sizeof': self.sizeof_method,
+                             'get_define': self.get_define_method,
                              'has_header': self.has_header_method,
                              'has_header_symbol': self.has_header_symbol_method,
                              'run': self.run_method,
@@ -865,6 +866,20 @@ class CompilerHolder(InterpreterObject):
         mlog.log('Checking for size of "%s": %d' % (element, esize))
         return esize
 
+    def get_define_method(self, args, kwargs):
+        if len(args) != 1:
+            raise InterpreterException('get_define() takes exactly one argument.')
+        check_stringlist(args)
+        element = args[0]
+        prefix = kwargs.get('prefix', '')
+        if not isinstance(prefix, str):
+            raise InterpreterException('Prefix argument of get_define() must be a string.')
+        extra_args = self.determine_args(kwargs)
+        deps = self.determine_dependencies(kwargs)
+        value = self.compiler.get_define(element, prefix, self.environment, extra_args, deps)
+        mlog.log('Checking for value of define "%s": %s' % (element, value))
+        return value
+
     def compiles_method(self, args, kwargs):
         if len(args) != 1:
             raise InterpreterException('compiles method takes exactly one argument.')
diff --git a/test cases/common/140 get define/meson.build b/test cases/common/140 get define/meson.build
new file mode 100644
index 0000000..0d83b8d
--- /dev/null
+++ b/test cases/common/140 get define/meson.build
@@ -0,0 +1,19 @@
+project('get define', 'c', 'cpp')
+
+host_system = host_machine.system()
+
+foreach lang : ['c', 'cpp']
+  cc = meson.get_compiler(lang)
+  if host_system == 'linux'
+    d = cc.get_define('__linux__')
+    assert(d == '1', '__linux__ value is @0@ instead of 1'.format(d))
+  elif host_system == 'darwin'
+    d = cc.get_define('__APPLE__')
+    assert(d == '1', '__APPLE__ value is @0@ instead of 1'.format(d))
+  elif host_system == 'windows'
+    d = cc.get_define('_WIN32')
+    assert(d == '1', '_WIN32 value is @0@ instead of 1'.format(d))
+  else
+    error('Please report a bug and help us improve support for this platform')
+  endif
+endforeach