cert.py: Added INT-31-C check, ensure that integer conversions do not result in lost or misinterpreted data

addons/cert.py

@@ -17,6 +17,12 @@ 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
@@ -49,6 +55,12 @@ def isBitwiseOp(token):
 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
@@ -79,6 +91,38 @@ def exp46(data):
             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)
@@ -87,3 +131,4 @@ for arg in sys.argv[1:]:
             print('Checking ' + arg + ', config "' + cfg.name + '"...')
         exp42(cfg)
         exp46(cfg)
+        int31(cfg, data.platform)