clangd enhancements. (qmk#23310)

.clangd

@@ -1,4 +1,4 @@
 CompileFlags:
   Add: [-Wno-unknown-attributes, -Wno-maybe-uninitialized, -Wno-unknown-warning-option]
-  Remove: [-W*, -mcall-prologues]
+  Remove: [-W*, -mmcu=*, -mcpu=*, -mfpu=*, -mfloat-abi=*, -mno-unaligned-access, -mno-thumb-interwork, -mcall-prologues]
   Compiler: clang

lib/python/qmk/cli/generate/compilation_database.py

@@ -25,7 +25,6 @@ def system_libs(binary: str) -> List[Path]:
     """Find the system include directory that the given build tool uses.
     """
     cli.log.debug("searching for system library directory for binary: %s", binary)
-    bin_path = shutil.which(binary)
 
     # Actually query xxxxxx-gcc to find its include paths.
     if binary.endswith("gcc") or binary.endswith("g++"):
@@ -37,7 +36,31 @@ def system_libs(binary: str) -> List[Path]:
                 paths.append(Path(line.strip()).resolve())
         return paths
 
-    return list(Path(bin_path).resolve().parent.parent.glob("*/include")) if bin_path else []
+    return list(Path(binary).resolve().parent.parent.glob("*/include")) if binary else []
+
+
+@lru_cache(maxsize=10)
+def cpu_defines(binary: str, compiler_args: str) -> List[str]:
+    cli.log.debug("gathering definitions for compilation: %s %s", binary, compiler_args)
+    if binary.endswith("gcc") or binary.endswith("g++"):
+        invocation = [binary, '-dM', '-E']
+        if binary.endswith("gcc"):
+            invocation.extend(['-x', 'c'])
+        elif binary.endswith("g++"):
+            invocation.extend(['-x', 'c++'])
+        compiler_args = shlex.split(compiler_args)
+        invocation.extend(compiler_args)
+        invocation.append('-')
+        result = cli.run(invocation, capture_output=True, check=True, stdin=None, input='\n')
+        define_args = []
+        for line in result.stdout.splitlines():
+            line_args = line.split(' ', 2)
+            if len(line_args) == 3 and line_args[0] == '#define':
+                define_args.append(f'-D{line_args[1]}={line_args[2]}')
+            elif len(line_args) == 2 and line_args[0] == '#define':
+                define_args.append(f'-D{line_args[1]}')
+        return list(sorted(set(define_args)))
+    return []
 
 
 file_re = re.compile(r'printf "Compiling: ([^"]+)')
@@ -68,9 +91,12 @@ def parse_make_n(f: Iterator[str]) -> List[Dict[str, str]]:
                 # we have a hit!
                 this_cmd = m.group(1)
                 args = shlex.split(this_cmd)
-                for s in system_libs(args[0]):
+                binary = shutil.which(args[0])
+                compiler_args = set(filter(lambda x: x.startswith('-m') or x.startswith('-f'), args))
+                for s in system_libs(binary):
                     args += ['-isystem', '%s' % s]
-                new_cmd = ' '.join(shlex.quote(s) for s in args if s != '-mno-thumb-interwork')
+                args.extend(cpu_defines(binary, ' '.join(shlex.quote(s) for s in compiler_args)))
+                new_cmd = ' '.join(shlex.quote(s) for s in args)
                 records.append({"directory": str(QMK_FIRMWARE.resolve()), "command": new_cmd, "file": this_file})
                 state = 'start'