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>

1 files changed, 50 insertions, 10 deletions

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