cmake: Log warnings in CMakeLists.txt

Previously, warnings genereated in CMake were not logged because
CMake sends them to stderr alongside the trace information. With
this PR, only real trace lines are send to the trace parser and
all other lines in stderr are logged as warnings.

mesonbuild/cmake/interpreter.py

@@ -51,6 +51,20 @@ if TYPE_CHECKING:
     from ..build import Build
     from ..backend.backends import Backend
 
+# Disable all warnings automaticall enabled with --trace and friends
+# See https://cmake.org/cmake/help/latest/variable/CMAKE_POLICY_WARNING_CMPNNNN.html
+disable_policy_warnings = [
+    'CMP0025',
+    'CMP0047',
+    'CMP0056',
+    'CMP0060',
+    'CMP0065',
+    'CMP0066',
+    'CMP0067',
+    'CMP0082',
+    'CMP0089',
+]
+
 backend_generator_map = {
     'ninja': 'Ninja',
     'xcode': 'Xcode',
@@ -503,6 +517,8 @@ class CMakeInterpreter:
 
         generator = backend_generator_map[self.backend_name]
         cmake_args = cmake_exe.get_command()
+        trace_args = ['--trace', '--trace-expand', '--no-warn-unused-cli']
+        cmcmp_args = ['-DCMAKE_POLICY_WARNING_{}=OFF'.format(x) for x in disable_policy_warnings]
 
         if version_compare(cmake_exe.version(), '>=3.14'):
             self.cmake_api = CMakeAPI.FILE
@@ -523,7 +539,6 @@ class CMakeInterpreter:
                 cmake_args += ['-DCMAKE_LINKER={}'.format(comp.get_linker_exelist()[0])]
         cmake_args += ['-G', generator]
         cmake_args += ['-DCMAKE_INSTALL_PREFIX={}'.format(self.install_prefix)]
-        cmake_args += ['--trace', '--trace-expand']
         cmake_args += extra_cmake_options
 
         # Run CMake
@@ -531,11 +546,16 @@ class CMakeInterpreter:
         with mlog.nested():
             mlog.log('Configuring the build directory with', mlog.bold('CMake'), 'version', mlog.cyan(cmake_exe.version()))
             mlog.log(mlog.bold('Running:'), ' '.join(cmake_args))
+            mlog.log(mlog.bold('  - build directory:         '), self.build_dir)
+            mlog.log(mlog.bold('  - source directory:        '), self.src_dir)
+            mlog.log(mlog.bold('  - trace args:              '), ' '.join(trace_args))
+            mlog.log(mlog.bold('  - disabled policy warnings:'), '[{}]'.format(', '.join(disable_policy_warnings)))
             mlog.log()
             os.makedirs(self.build_dir, exist_ok=True)
             os_env = os.environ.copy()
             os_env['LC_ALL'] = 'C'
-            proc = Popen(cmake_args + [self.src_dir], stdout=PIPE, stderr=PIPE, cwd=self.build_dir, env=os_env)
+            final_command = cmake_args + trace_args + cmcmp_args + [self.src_dir]
+            proc = Popen(final_command, stdout=PIPE, stderr=PIPE, cwd=self.build_dir, env=os_env)
 
             def print_stdout():
                 while True:
@@ -548,8 +568,23 @@ class CMakeInterpreter:
             t = Thread(target=print_stdout)
             t.start()
 
-            self.raw_trace = proc.stderr.read()
-            self.raw_trace = self.raw_trace.decode('utf-8')
+            # Read stderr line by line and log non trace lines
+            self.raw_trace = ''
+            tline_start_reg = re.compile(r'^\s*(.*\.(cmake|txt))\(([0-9]+)\):\s*(\w+)\(.*$')
+            inside_multiline_trace = False
+            while True:
+                line = proc.stderr.readline()
+                if not line:
+                    break
+                line = line.decode('utf-8')
+                if tline_start_reg.match(line):
+                    self.raw_trace += line
+                    inside_multiline_trace = not line.endswith(' )\n')
+                elif inside_multiline_trace:
+                    self.raw_trace += line
+                else:
+                    mlog.warning(line.strip('\n'))
+
             proc.stderr.close()
             proc.wait()