Bug 1578876 - add exception for Decimal code to check_vanilla_allocations.py; r=njn

Calls to these allocation functions from mozglue can generally be ignored.

Differential Revision: https://phabricator.services.mozilla.com/D45207

--HG--
extra : moz-landing-system : lando

Author: froydnj

config/check_vanilla_allocations.py

@@ -10,7 +10,9 @@
 # go through that custom allocator.
 #
 # Therefore, the presence of any calls to "vanilla" allocation/free functions
-# (e.g. malloc(), free()) is a bug.
+# from within SpiderMonkey itself (e.g. malloc(), free()) is a bug.  Calls from
+# within mozglue and non-SpiderMonkey locations are fine; there is a list of
+# exceptions that can be added to as the need arises.
 #
 # This script checks for the presence of such disallowed vanilla
 # allocation/free function in SpiderMonkey when it's built as a library.  It
@@ -159,6 +161,10 @@ def main():
         if filename == 'umutex.o':
             continue
 
+        # Ignore allocations from decimal conversion functions inside mozglue.
+        if filename == 'Decimal.o':
+            continue
+
         fn = m.group(2)
         if filename == 'jsutil.o':
             jsutil_cpp.add(fn)