Break Clang

breakclang.py

import subprocess
import os

ARGMAX = os.sysconf("SC_ARG_MAX")

class TestClang(object):

  def __init__(self):
    llvmMax = ARGMAX / 2
    self.testArgument = "-DE"
    self.responseFile = "arguments.resp"
    self.nArgs = llvmMax / (len(self.testArgument) + 1)
    self.args = ["clang++", "test.cc", "-o", "test", "@%s" % self.responseFile]

  def generateResponseFile(self, nargs):
    with open(self.responseFile, 'w') as respFile:
      for i in range(nargs):
        respFile.write("%s\n" % self.testArgument)

  def runClang(self, nargs):
    self.generateResponseFile(nargs)
    return subprocess.call(self.args)

  def findFailure(self):
    # walk backward from the approximate LLVM limit until the failure is found
    for i in range(self.nArgs, 0, -10000):
      exitcode = self.runClang(i)
      print i
      if exitcode != 0:
        print "Clang failed: ", " ".join(self.args)
        print "Number of arguments in response file: ", i
        return

test = TestClang()
test.findFailure()