meson: move sparse detection to Meson and rewrite check_sparse.py

Pass the path to the program to scripts/check_sparse.py, which
previously was not included in config-host.mak.  Change
scripts/check_sparse.py to work with cgcc, which seems to
work better with sparse 0.6.x.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

scripts/check_sparse.py

@@ -1,25 +1,59 @@
 #! /usr/bin/env python3
 
-# Invoke sparse based on the contents of compile_commands.json
+# Invoke sparse based on the contents of compile_commands.json,
+# also working around several deficiencies in cgcc's command line
+# parsing
 
 import json
 import subprocess
+import os
 import sys
 import shlex
 
-def extract_cflags(shcmd):
-    cflags = shlex.split(shcmd)
-    return [x for x in cflags
-            if x.startswith('-D') or x.startswith('-I') or x.startswith('-W')
-               or x.startswith('-std=')]
+def cmdline_for_sparse(sparse, cmdline):
+    # Do not include the C compiler executable
+    skip = True
+    arg = False
+    out = sparse + ['-no-compile']
+    for x in cmdline:
+        if arg:
+            out.append(x)
+            arg = False
+            continue
+        if skip:
+            skip = False
+            continue
+        # prevent sparse from treating output files as inputs
+        if x == '-MF' or x == '-MQ' or x == '-o':
+            skip = True
+            continue
+        # cgcc ignores -no-compile if it sees -M or -MM?
+        if x.startswith('-M'):
+            continue
+        # sparse does not understand these!
+        if x == '-iquote' or x == '-isystem':
+            x = '-I'
+        if x == '-I':
+            arg = True
+        out.append(x)
+    return out
 
-cflags = sys.argv[1:-1]
-with open(sys.argv[-1], 'r') as fd:
+root_path = os.getenv('MESON_BUILD_ROOT')
+def build_path(s):
+    return s if not root_path else os.path.join(root_path, s)
+
+ccjson_path = build_path(sys.argv[1])
+with open(ccjson_path, 'r') as fd:
     compile_commands = json.load(fd)
 
+sparse = sys.argv[2:]
+sparse_env = os.environ.copy()
 for cmd in compile_commands:
-    cmd = ['sparse'] + cflags + extract_cflags(cmd['command']) + [cmd['file']]
-    print(' '.join((shlex.quote(x) for x in cmd)))
-    r = subprocess.run(cmd)
+    cmdline = shlex.split(cmd['command'])
+    cmd = cmdline_for_sparse(sparse, cmdline)
+    print('REAL_CC=%s' % shlex.quote(cmdline[0]),
+          ' '.join((shlex.quote(x) for x in cmd)))
+    sparse_env['REAL_CC'] = cmdline[0]
+    r = subprocess.run(cmd, env=sparse_env, cwd=root_path)
     if r.returncode != 0:
         sys.exit(r.returncode)