Fix for the -fvisibility=hidden problem.

'man ld' revealed the secret. Flag -keep_private_externs seems to
do what we want.

Author: BrunoDutertre

driver/utils.py

@@ -192,7 +192,8 @@ def __init__(self, inputList, exactMatches={}, patternMatches={}):
             '-current_version' : (1, ArgumentListFilter.linkBinaryCallback),
             '-compatibility_version' : (1, ArgumentListFilter.linkBinaryCallback),
 
-            # bd: need to warn the darwin user that these flags will rain on their parade
+            #
+            # BD: need to warn the darwin user that these flags will rain on their parade
             # (the Darwin ld is a bit single minded)
             #
             # 1) compilation with -fvisibility=hidden causes trouble when we try to
@@ -202,7 +203,9 @@ def __init__(self, inputList, exactMatches={}, patternMatches={}):
             # 2) all stripping commands (e.g., -dead_strip) remove the __LLVM segment after
             #    linking
             #
-            '-fvisibility=hidden' :  (0, ArgumentListFilter.darwinWarningCompileUnaryCallback),
+            # Update: found a fix for problem 1: add flag -keep_private_externs when
+            # calling ld -r.
+            #
             '-Wl,-dead_strip' :  (0, ArgumentListFilter.darwinWarningLinkUnaryCallback),
 
            }
@@ -490,7 +493,7 @@ def attachBitcodePathToObject(bcPath, outFileName):
 
     # Now write our bitcode section
     if (sys.platform.startswith('darwin')):
-        objcopyCmd = ['ld', '-r', outFileName, '-sectcreate', darwinSegmentName, darwinSectionName,  f.name, '-o', outFileName]
+        objcopyCmd = ['ld', '-r', '-keep_private_externs', outFileName, '-sectcreate', darwinSegmentName, darwinSectionName,  f.name, '-o', outFileName]
     else:
         objcopyCmd = ['objcopy', '--add-section', '{0}={1}'.format(elfSectionName, f.name), outFileName]
     orc = 0