build: rework Makefile var extraction... again

*sigh* I can't seem to catch a break on this.  Add a regex variant.

Signed-off-by: David Lamparter <equinox@opensourcerouting.org>

2 files changed, 53 insertions, 16 deletions

diff --git a/python/makefile.py b/python/makefile.py
index 9af397d373..e60c8aadbc 100644
--- a/python/makefile.py
+++ b/python/makefile.py
@@ -11,6 +11,7 @@ import subprocess
 import re
 import argparse
 from string import Template
+from makevars import MakeReVars
 
 argp = argparse.ArgumentParser(description = 'FRR Makefile extensions')
 argp.add_argument('--dev-build', action = 'store_const', const = True,
@@ -20,13 +21,9 @@ args = argp.parse_args()
 with open('Makefile', 'r') as fd:
     before = fd.read()
 
-nolinecont = before.replace('\\\n', '')
-m = re.search('^clippy_scan\s*=([^#]*)(?:#.*)?$', nolinecont, flags=re.MULTILINE)
-if m is None:
-    sys.stderr.write('failed to parse Makefile.in\n')
-    sys.exit(2)
+mv = MakeReVars(before)
 
-clippy_scan = m.group(1).strip().split()
+clippy_scan = mv['clippy_scan'].strip().split()
 for clippy_file in clippy_scan:
     assert clippy_file.endswith('.c')
 
diff --git a/python/makevars.py b/python/makevars.py
index e0e2031a0d..1a85fbd6f5 100644
--- a/python/makevars.py
+++ b/python/makevars.py
@@ -4,14 +4,33 @@
 
 import os
 import subprocess
+import re
 
-class MakeVars(object):
+class MakeVarsBase(object):
     '''
-    makevars['FOO_CFLAGS'] gets you "FOO_CFLAGS" from Makefile
+    common code between MakeVars and MakeReVars
     '''
     def __init__(self):
         self._data = dict()
 
+    def __getitem__(self, k):
+        if k not in self._data:
+            self.getvars([k])
+        return self._data[k]
+
+    def get(self, k, defval = None):
+        if k not in self._data:
+            self.getvars([k])
+        return self._data.get(k) or defval
+
+class MakeVars(MakeVarsBase):
+    '''
+    makevars['FOO_CFLAGS'] gets you "FOO_CFLAGS" from Makefile
+
+    This variant works by invoking make as a subprocess, i.e. Makefile must
+    be valid and working.  (This is sometimes a problem if depfiles have not
+    been generated.)
+    '''
     def getvars(self, varlist):
         '''
         get a batch list of variables from make.  faster than individual calls.
@@ -39,12 +58,33 @@ class MakeVars(object):
             v = v[1:-1]
             self._data[k] = v
 
-    def __getitem__(self, k):
-        if k not in self._data:
-            self.getvars([k])
-        return self._data[k]
+class MakeReVars(MakeVarsBase):
+    '''
+    makevars['FOO_CFLAGS'] gets you "FOO_CFLAGS" from Makefile
 
-    def get(self, k, defval = None):
-        if k not in self._data:
-            self.getvars([k])
-        return self._data[k] or defval
+    This variant works by regexing through Makefile.  This means the Makefile
+    does not need to be fully working, but on the other hand it doesn't support
+    fancy complicated make expressions.
+    '''
+    var_re = re.compile(r'^([^=#\n\s]+)[ \t]*=[ \t]*([^#\n]*)(?:#.*)?$', flags=re.MULTILINE)
+    repl_re = re.compile(r'\$(?:([A-Za-z])|\(([^\)]+)\))')
+
+    def __init__(self, maketext):
+        super().__init__()
+        self._vars = dict(self.var_re.findall(maketext.replace('\\\n', '')))
+
+    def replacevar(self, match):
+        varname = match.group(1) or match.group(2)
+        return self._vars.get(varname, '')
+
+    def getvars(self, varlist):
+        for varname in varlist:
+            if varname not in self._vars:
+                continue
+
+            val, prevval = self._vars[varname], None
+            while val != prevval:
+                prevval = val
+                val = self.repl_re.sub(self.replacevar, val)
+
+            self._data[varname] = val