Software Metrics

Compute common software complexity metrics. Right now, the Halstead metric (see here and here) and McCabe's cyclomatic complexity metric are available.

OptionArgumentsDescription
--Transform SoftwareMetrics Compute software complexity metrics for a function.
--SoftwareMetricKind raw, halstead, mccabe What metric to compute. Default=halstead,mccabe.
  • raw = Raw counts of tokens, identifiers, etc.
  • halstead = The Halstead metric.
  • mccabe = McCabe's Cyclomatric Complexity metric.
--SoftwareMetricFileName string On which file to print the metrics. If not set, print to standard output. From version 3.3. Default=Stdout.
--SoftwareMetricJsonFileName string On which file to print the metrics in Json format. From version 3.3. Default=Stdout.

Example

Here is an example where we print out the McCabe metric for three functions: the original fib, fib after flattning, and fib after virtualization. Here is the tigress command: 

tigress \
        --Transform=SoftwareMetrics \
           --Functions=fib \
           --SoftwareMetricsFileName=original.txt \
           --SoftwareMetricsKind=mccabe \
        --Transform=Copy \
           --Functions=fib \
           --CopyName=fib2 \
        --Transform=Flatten \
           --Functions=fib \
        --Transform=SoftwareMetrics \
           --Functions=fib \
           --SoftwareMetricsFileName=flatten.txt \
           --SoftwareMetricsKind=mccabe \
        --Transform=Virtualize \
           --Functions=fib2 \
        --Transform=SoftwareMetrics \
           --Functions=fib2 \
           --SoftwareMetricsFileName=virtualize.txt \
           --SoftwareMetricsKind=mccabe \
        test1.c --out=obf.c

And here are the results (the variables are the same as seen here and here): 

> cat original.txt 
McCabe.fib.E = 10
McCabe.fib.N = 10
McCabe.fib.P = 1
McCabe.fib.value = 2
> cat flatten.txt 
McCabe.fib.E = 28
McCabe.fib.N = 22
McCabe.fib.P = 1
McCabe.fib.value = 8
> cat virtualize.txt 
McCabe.fib2.E = 85
McCabe.fib2.N = 68
McCabe.fib2.P = 1
McCabe.fib2.value = 19

These metrics can be used to see how much change each transformation incurs.

Example in Json (From version 3.3)

You can also generate the output into a Json file which is useful if you want to process them with some other program: 

tigress \
        --Transform=SoftwareMetrics \
           --Functions=wikipedia,sort,main \
           --SoftwareMetricsJsonFileName=metrics.json \
           --SoftwareMetricsKind=raw,halstead,mccabe \
        test1.c --out=obf.c

> cat metrics.json
...
{
   "metric": "McCabe", 
   "name": "sort", 
   "E": 24, 
   "N": 21,
   "P": 1, 
   "value": 5 
}
...
 

Issues

Don't expect the values computed by this transform to be identical to that produced by other tools. It only makes sense to compare the metrics computed by Tigress with other metrics computed by Tigress:

  • The control flow graphs we build will be different than those produced by other tools - this affects the McCabe metric.
  • We're computing token counts over CIL's abstract syntax tree, not over the raw C source. This affects the Halstead metric since CIL performs various simplifications of the code, such as folding while/do/for into one loop.