[clang][utils] Make CmpDriver Python3 compatible

[DavidSpickett]

The majority of this is running 2to3 on it:

• print is a function in 3.x
• next(it) instead of it.next()

Then there was a use of "map(None, iterables..)"
which in Python 2 was a way of saying
"combine these iterables, and if one is shorter,
pad with None".

This no longer works in Python3, the equivalent
is zip_longest:
https://docs.python.org/3/library/itertools.html#itertools.zip_longest

fillvalue defaults to None but I made it explicit
since it may help someone debugging this script
in future.

(I doubt it has been used for a very long time)

[llvmbot]

@llvm/pr-subscribers-clang

Author: David Spickett (DavidSpickett)

Changes

The majority of this is running 2to3 on it:

• print is a function in 3.x
• next(it) instead of it.next()

Then there was a use of "map(None, iterables..)"
which in Python 2 was a way of saying
"combine these iterables, and if one is shorter,
pad with None".

This no longer works in Python3, the equivalent
is zip_longest:
https://docs.python.org/3/library/itertools.html#itertools.zip_longest

fillvalue defaults to None but I made it explicit
since it may help someone debugging this script
in future.

(I doubt it has been used for a very long time)

---

Full diff: https://github.com/llvm/llvm-project/pull/163740.diff

1 Files Affected:

• (modified) clang/utils/CmpDriver (+32-31)

diff --git a/clang/utils/CmpDriver b/clang/utils/CmpDriver
index 12ce7a3250f66..0732baa76d01c 100755
--- a/clang/utils/CmpDriver
+++ b/clang/utils/CmpDriver
@@ -5,6 +5,7 @@ A simple utility that compares tool invocations and exit codes issued by
 compiler drivers that support -### (e.g. gcc and clang).
 """
 
+from itertools import zip_longest
 import subprocess
 
 def splitArgs(s):
@@ -22,7 +23,7 @@ def splitArgs(s):
         elif inQuote:
             if c == '\\':
                 current += c
-                current += it.next()
+                current += next(it)
             else:
                 current += c
         elif not c.isspace():
@@ -135,77 +136,77 @@ def main():
 
     # Compare stdout.
     if infoA.stdout != infoB.stdout:
-        print '-- STDOUT DIFFERS -'
-        print 'A OUTPUT: ',infoA.stdout
-        print 'B OUTPUT: ',infoB.stdout
-        print
+        print('-- STDOUT DIFFERS -')
+        print('A OUTPUT: ',infoA.stdout)
+        print('B OUTPUT: ',infoB.stdout)
+        print()
 
         diff = ZipperDiff(infoA.stdout.split('\n'),
                           infoB.stdout.split('\n'))
         for i,(aElt,bElt) in enumerate(diff.getDiffs()):
             if aElt is None:
-                print 'A missing: %s' % bElt
+                print('A missing: %s' % bElt)
             elif bElt is None:
-                print 'B missing: %s' % aElt
+                print('B missing: %s' % aElt)
             else:
-                print 'mismatch: A: %s' % aElt
-                print '          B: %s' % bElt
+                print('mismatch: A: %s' % aElt)
+                print('          B: %s' % bElt)
 
         differ = True
 
     # Compare stderr.
     if infoA.stderr != infoB.stderr:
-        print '-- STDERR DIFFERS -'
-        print 'A STDERR: ',infoA.stderr
-        print 'B STDERR: ',infoB.stderr
-        print
+        print('-- STDERR DIFFERS -')
+        print('A STDERR: ',infoA.stderr)
+        print('B STDERR: ',infoB.stderr)
+        print()
 
         diff = ZipperDiff(infoA.stderr.split('\n'),
                           infoB.stderr.split('\n'))
         for i,(aElt,bElt) in enumerate(diff.getDiffs()):
             if aElt is None:
-                print 'A missing: %s' % bElt
+                print('A missing: %s' % bElt)
             elif bElt is None:
-                print 'B missing: %s' % aElt
+                print('B missing: %s' % aElt)
             else:
-                print 'mismatch: A: %s' % aElt
-                print '          B: %s' % bElt
+                print('mismatch: A: %s' % aElt)
+                print('          B: %s' % bElt)
 
         differ = True
 
     # Compare commands.
-    for i,(a,b) in enumerate(map(None, infoA.commands, infoB.commands)):
+    for i,(a,b) in enumerate(zip_longest(infoA.commands, infoB.commands, fillvalue=None)):
         if a is None:
-            print 'A MISSING:',' '.join(b)
+            print('A MISSING:',' '.join(b))
             differ = True
             continue
         elif b is None:
-            print 'B MISSING:',' '.join(a)
+            print('B MISSING:',' '.join(a))
             differ = True
             continue
 
         diff = DriverZipperDiff(a,b)
         diffs = list(diff.getDiffs())
         if diffs:
-            print '-- COMMAND %d DIFFERS -' % i
-            print 'A COMMAND:',' '.join(a)
-            print 'B COMMAND:',' '.join(b)
-            print
+            print('-- COMMAND %d DIFFERS -' % i)
+            print('A COMMAND:',' '.join(a))
+            print('B COMMAND:',' '.join(b))
+            print()
             for i,(aElt,bElt) in enumerate(diffs):
                 if aElt is None:
-                    print 'A missing: %s' % bElt
+                    print('A missing: %s' % bElt)
                 elif bElt is None:
-                    print 'B missing: %s' % aElt
+                    print('B missing: %s' % aElt)
                 else:
-                    print 'mismatch: A: %s' % aElt
-                    print '          B: %s' % bElt
+                    print('mismatch: A: %s' % aElt)
+                    print('          B: %s' % bElt)
             differ = True
     
     # Compare result codes.
     if infoA.exitCode != infoB.exitCode:
-        print '-- EXIT CODES DIFFER -'
-        print 'A: ',infoA.exitCode
-        print 'B: ',infoB.exitCode
+        print('-- EXIT CODES DIFFER -')
+        print('A: ',infoA.exitCode)
+        print('B: ',infoB.exitCode)
         differ = True
 
     if differ:

[DavidSpickett]

There's an argument to leave these old scripts exactly as they are, but in this case the changes are straightforward enough that I'd like to do them anyway.

This will make it easier to use Python compatibility checking tools on llvm-project, and save someone some work if the script is rediscovered.