#!/usr/bin/env python
#
# Cert: Some extra CERT checkers
#
# Cppcheck itself handles many CERT rules. Cppcheck warns when there is undefined behaviour.
#
# Example usage of this addon (scan a sourcefile main.cpp)
# cppcheck --dump main.cpp
# python cert.py main.cpp.dump

import cppcheckdata
import sys
import re


def reportError(token, severity, msg, id):
    sys.stderr.write(
        '[' + token.file + ':' + str(token.linenr) + '] (' + severity + '): ' + msg + ' [' + id + ']\n')

def simpleMatch(token, pattern):
    for p in pattern.split(' '):
        if not token or token.str != p:
            return False
        token = token.next
    return True

def isUnpackedStruct(var):
    decl = var.typeStartToken
    while decl and decl.isName:
        if decl.str == 'struct':
            structScope = decl.next.typeScope
            if structScope:
                linenr = int(structScope.classStart.linenr)
                for line in open(structScope.classStart.file):
                    linenr -= 1
                    if linenr == 0:
                        return True
                    if re.match(r'#pragma\s+pack\s*\(', line):
                        return False
            break
        decl = decl.next
    return False


def isLocalUnpackedStruct(arg):
    if arg and arg.str == '&' and not arg.astOperand2:
        arg = arg.astOperand1
    return arg and arg.variable and (arg.variable.isLocal or arg.variable.isArgument) and isUnpackedStruct(arg.variable)


def isBitwiseOp(token):
    return token and (token.str in {'&', '|', '^'})


def isComparisonOp(token):
    return token and (token.str in {'==', '!=', '>', '>=', '<', '<='})

def isCast(expr):
    if not expr or expr.str != '(' or not expr.astOperand1 or expr.astOperand2:
        return False
    if simpleMatch(expr, '( )'):
        return False
    return True

# EXP42-C
# do not compare padding data
def exp42(data):
    for token in data.tokenlist:
        if token.str != '(' or not token.astOperand1:
            continue

        arg1 = None
        arg2 = None
        if token.astOperand2 and token.astOperand2.str == ',':
            if token.astOperand2.astOperand1 and token.astOperand2.astOperand1.str == ',':
                arg1 = token.astOperand2.astOperand1.astOperand1
                arg2 = token.astOperand2.astOperand1.astOperand2

        if token.astOperand1.str == 'memcmp' and (isLocalUnpackedStruct(arg1) or isLocalUnpackedStruct(arg2)):
            reportError(
                token, 'style', "Comparison of struct padding data " +
                "(fix either by packing the struct using '#pragma pack' or by rewriting the comparison)", 'cert-EXP42-C')


# EXP46-C
# Do not use a bitwise operator with a Boolean-like operand
#   int x = (a == b) & c;
def exp46(data):
    for token in data.tokenlist:
        if isBitwiseOp(token) and (isComparisonOp(token.astOperand1) or isComparisonOp(token.astOperand2)):
            reportError(
                token, 'style', 'Bitwise operator is used with a Boolean-like operand', 'cert-EXP46-c')

# INT31-C
# Ensure that integer conversions do not result in lost or misinterpreted data
def int31(data, platform):
    if not platform:
        return
    for token in data.tokenlist:
        if not isCast(token):
            continue
        if not token.valueType or not token.astOperand1.values:
            continue
        bits = None
        if token.valueType.type == 'char':
            bits = platform.char_bit
        elif token.valueType.type == 'short':
            bits = platform.short_bit
        elif token.valueType.type == 'int':
            bits = platform.int_bit
        elif token.valueType.type == 'long':
            bits = platform.long_bit
        else:
            continue
        if bits >= 64:
            continue
        maxval = (1 << (bits - 1) - 1)
        for value in token.astOperand1.values:
            if value.intvalue > maxval:
                reportError(
                    token,
                    'style',
                    'Loss of information when casting ' + str(value.intvalue) + ' to ' + token.valueType.type,
                    'cert-INT31-c')

for arg in sys.argv[1:]:
    print('Checking ' + arg + '...')
    data = cppcheckdata.parsedump(arg)
    for cfg in data.configurations:
        if len(data.configurations) > 1:
            print('Checking ' + arg + ', config "' + cfg.name + '"...')
        exp42(cfg)
        exp46(cfg)
        int31(cfg, data.platform)