Category Archives: C++

How much code can a coder code?

Lines of code (LOC) is a simple way to measure programmer productivity. Admittedly it is a flawed metric. As Bill Gates famously said “Measuring programming progress by lines of code is like measuring aircraft building progress by weight”. But it is at least easy to measure.

So how much code do programmers average per day?

  • Fred Brooks claimed in ‘The Mythical Man-Month’ that programmers working on the OS/360 operating system averaged around 10 LOC per day.
  • Capers Jones measured productivity of around 16 to 38 LOC per day across a range of projects.
  • McConnell measured productivity of 20 to 125 LOC per day for small projects (10,000 LOC) through to 1.5 to 25 LOC per day for large projects (10,000,000 LOC).

It doesn’t sound a lot, does it? I’m sure I’ve written hundreds of lines of code on some days. I wondered how my productivity compared. So I did some digging through my own code. In the last 12 years I have written somewhere between 90,000 and 150,000 C++ LOC (depending on how you measure LOC) for my products: PerfectTablePlan, Hyper Plan and Keyword Funnel. This is an average of round 50 lines of code per working day. Not so different from the data above.

I also looked at how PerfectTablePlan LOC increased over time. I was expecting it to show a marked downward trend in productivity as the code base got bigger, as predicted by McConnell’s data. I was surprised to see that this was not the case, with LOC per day remaining pretty constant as the code base increased in size from 25k to 125k.

loc

Some qualifications:

  • I give a range for LOC because ‘line of code’ isn’t very well defined. Do you count only executable statements, or any lines of source that aren’t blank?
  • My data is based on the current sizes of the code bases. It doesn’t include all the code I have written and then deleted in the last 12 years. I have just spent several months rewriting large parts of PerfectTablePlan to work with the latest version of Qt, which involved deleting large swathes of code.
  • It doesn’t include automatically generated code (e.g. code generated by the Qt framework for user interfaces and signals/slots code).
  • I only counted code in products shipped to the user. I didn’t count code I wrote for licence generation, testing etc.
  • All the code is cross-platform for Windows and Mac, which makes it more time consuming to write, test and document.
  • Programming is only one of the things I do. As a one-man-band I also do marketing, sales, QA, support, documentation, newsletters, admin and nearly everything else. I have also done some consulting and training not directly related to my products in the last 12 years.

Given that I probably spend less than half my time developing (I have never measured the ratio), my productivity seems fairly good. I think a lot of this may be the fact that, as a solo developer, I don’t have to waste time with meetings, corporate bullshit and trying to understand other people’s code. Also writing desktop Windows/Mac applications in C++ is a lot easier than writing an new operating system with 1970s tools.

50 lines of code per day doesn’t sound like a lot. But the evidence is that you are unlikely to do much better on a substantial project over an extended period. Bear that in mind next time you estimate how long something is going to take.

If you have data on LOC per day for sizeable projects worked on over an extended period, please post it in the comments. It will only take you a few minutes to get the stats using Source Monitor (which is free).

 

 

 

 

 

 

Pretty printing C++ with Clang-Format

I use some of the code generation and refactoring tools in QtCreator. These save a lot of time, but they don’t format C++ code how I like it. For example they produce C++ code like this:

void MyClass::foo(int *x)

But I like my code formatted like this:

void MyClass::foo( int* x )

The differences may seem minor, but they are a source of significant irritation to me. I like my code how I like it, goddammit! And consistent formatting enhances readability. However re-formatting it by hand is time-consuming and tedious.

What I need is a tool that can enforce consistent formatting in the style that I like, or something close. I have tried to use automatic C++ formatting (pretty printing) tools in the past, but I couldn’t get them to produce a format that was close enough to what I wanted. But I have finally found the tool for the job. Clang-Format.

Clang-Format is part of the LLVM family of tools. It is a free, command-line tool that reformats C++, Objective-C or C according to the settings in a config file. As with many free tools, it isn’t terribly well documented. Some of the documentation on the web is out of date and some of it is incomplete. But I have managed to find out enough to configure it how I like it.

To run it you just need to place your options in a .clang-format file, make sure the clang-format executable is in the path and then run it:

clang-format.exe -i -style=file <C++ file>

Here are the settings I am currently using in my .clang-format file:

Language: Cpp
AccessModifierOffset: -4
AlignAfterOpenBracket: false
AlignConsecutiveAssignments: false
AlignConsecutiveDeclarations: false
AlignEscapedNewlinesLeft: false
AlignOperands: true
AlignTrailingComments: false
AllowAllParametersOfDeclarationOnNextLine: false
AllowShortBlocksOnASingleLine: false
AllowShortCaseLabelsOnASingleLine: false
AllowShortFunctionsOnASingleLine: Inline
AllowShortIfStatementsOnASingleLine: false
AllowShortLoopsOnASingleLine: false
AlwaysBreakAfterDefinitionReturnType: None
AlwaysBreakAfterReturnType: None
AlwaysBreakBeforeMultilineStrings: false
AlwaysBreakTemplateDeclarations: false
BinPackArguments: true
BinPackParameters: true
BraceWrapping:
  AfterClass:      true
  AfterControlStatement: true
  AfterEnum:       true
  AfterFunction:   true
  AfterNamespace:  true
  AfterObjCDeclaration: true
  AfterStruct:     true
  AfterUnion:      false
  BeforeCatch:     true
  BeforeElse:      true
  IndentBraces:    false
BreakBeforeBinaryOperators: None
BreakBeforeBraces: Allman
BreakBeforeTernaryOperators: true
BreakConstructorInitializersBeforeComma: false
ColumnLimit: 0
CommentPragmas: '^ IWYU pragma:'
ConstructorInitializerAllOnOneLineOrOnePerLine: false
ConstructorInitializerIndentWidth: 0
ContinuationIndentWidth: 4
Cpp11BracedListStyle: true
DerivePointerAlignment: false
DisableFormat: false
ExperimentalAutoDetectBinPacking: false
ForEachMacros: [ foreach, Q_FOREACH, BOOST_FOREACH ]
IndentCaseLabels: true
IndentWidth: 4
IndentWrappedFunctionNames: false
KeepEmptyLinesAtTheStartOfBlocks: true
MacroBlockBegin: ''
MacroBlockEnd: ''
MaxEmptyLinesToKeep: 2
NamespaceIndentation: None
PenaltyBreakBeforeFirstCallParameter: 100
PenaltyBreakComment: 300
PenaltyBreakFirstLessLess: 120
PenaltyBreakString: 1000
PenaltyExcessCharacter: 10000
PointerAlignment: Left
ReflowComments: true
SortIncludes: false
SpaceAfterCStyleCast: false
SpaceBeforeAssignmentOperators: true
SpaceBeforeParens: ControlStatements
SpaceInEmptyParentheses: false
SpacesBeforeTrailingComments: 1
SpacesInAngles: true
SpacesInContainerLiterals: true
SpacesInCStyleCastParentheses: true
SpacesInParentheses: true
SpacesInSquareBrackets: true
Standard: Cpp11
TabWidth: 4
UseTab: Never

It took me a few hours of fiddling with the settings to find the best combination. It would be really useful if someone could write a tool that would analyze your C++ code and create a .clang-format file for you. You would probably only want to do this once though, so I don’t think it has much potential as a commercial product.

There are only two things I couldn’t get quite right in the formatting:

  1. I couldn’t get it to add a blank line after public, protected and private declarations. I fixed this with a quick Perl hack (see below).
  2. I couldn’t get it to indent continuation lines how I would like (ideally indented 1 or 2 spaces from the first line). It is a small price to pay and I am just putting up with it for now.

Perhaps there are options to do these and I just didn’t find them.

Here is the Windows .bat script I used to format all the C++ files in a folder.

for %%f in (*.h *.cpp *.inl) do (
clang-format.exe -i -style=file %%f
)

for %%f in (*.h) do (
clang-format.exe -i -style=file %%f
perl -p -i.bak -e "s/public:/public:\n/g" %%f
perl -p -i.bak -e "s/protected:/protected:\n/g" %%f
perl -p -i.bak -e "s/private:/private:\n/g" %%f
perl -p -i.bak -e "s/    Q_OBJECT/Q_OBJECT/g" %%f
)

del *.bak
del *.tmp

No doubt there is a more elegant way to do the Perl, but it works.

I now just run this batch periodically to keep my code beautiful and consistent.

A code pretty printer product idea

I use QtCreator for my C++ development IDE. It is very good. But it doesn’t always lay out my C++ code the way I want it to. In particular the refactoring operations mess up my white space. I want my code to look like:

void foo( int* x, int& y )

But it keeps changing it to:

void foo(int *x, int &y)

Grrrrrr.

So I am constantly battling with QtCreator to layout my code how I like it. There are plenty of C++ pretty printers around. I played with some of the leading ones using UniversalIndentGUI, but I couldn’t get any of them to layout my code quite how I wanted. Maybe they could have done it, but I got fed up with fiddling with the settings.

What I need is a code pretty printer that I can configure to layout my code exactly how I want without me having to tweak 100 settings.

Ideally I want a code pretty printer that I can train. So I just point it at a few files of my code that are laid out how I want and it works out all my preferences (where to put braces, how to indent case statements, where to put the * for a pointer declaration etc) and can then apply them to any other code. It wouldn’t need a GUI. Or perhaps just enough to select the training files and then preview the results on other files.

I have no idea if this is a viable product idea. But I would pay $100 for it, if it worked well. Perhaps bigger software companies would pay a lot more? Or maybe something like this already exists and I just don’t know about it?

Cppcheck – A free static analyser for C and C++

I got a tip from Anna-Jayne Metcalfe of C++ and QA specialists Riverblade to check out Cppcheck, a free static analyser for C and C++. I ran >100 kLOC of PerfectTablePlan C++ through it and it picked up a few issues, including:

  • variables uninitialised in constructors
  • classes passed by value, rather than as a const reference
  • variables whose scopes could be reduced
  • methods that could be made const

It only took me a few minutes from downloading to getting results. And the results are a lot less noisy than lint. I’m impressed. PerfectTablePlan is heavily tested and I don’t think any of the issues found are the cause of bugs in PerfectTablePlan, but it shows the potential of the tool.

The documentation is here. But, on Windows, you just need to start the Cppcheck GUI (in C:\Program files\Cppcheck, they appear to be too modest to add a shortcut to your desktop), select Check>Directory… and browse to the source directory you want to check. Any issues found will then be displayed.

You can also set an editor to integrate with, in Edit>Preferences>Applications. Double clicking on an issue will then display the appropriate line in your editor of choice.

Cppdepend is available with a GUI on Windows and as a command line tool on a range of platforms. There is also an Eclipse plugin. See the sourceforge page for details on platforms and IDEs supported. You can even write your own Cppcheck rules.

Cppcheck could be a very valuable additional layer in my defence in depth approach to QA. I have added it to my checklist of things to do before each new release.

Programming skills wanted

I am looking to outsource some self-contained programming tasks in areas that I don’t have expertise in. I am hoping that someone reading this blog might be able to help (or know someone that can) so I don’t have to go through outsourcing sites. These are the two skills sets I am currently looking for:

  1. Javascript/CSS/HTML – To write a single page web app. This will have a relatively simple UI displaying data read from XML. The app will need to work on a wide range of browsers and devices. Ideally you should also have some web design skills, but this isn’t essential.
  2. C++/Qt 4/OpenGL – To write a relatively simple 3D visualization model that runs on Windows and Mac. This will involve populating a 3D space with specified shapes and allowing simple movement around it.

Details:

  • I am expecting that I will need 2 different people, but it is possible there might be someone out there with experience in both.
  • These are small projects (probably less than 2 weeks for task 1 and less than 1 week for task 2). But they might lead on to more work in future.
  • Time scales are reasonably relaxed. Ideally I would like the work to be finished by the end of September.
  • You can be based anywhere in the world, but must be able to communicate in English (written and spoken).
  • Full copyright to the work will pass to my company on full payment.
  • Obviously cost is an issue. If I have 2 promising candidates, I am likely to pick the cheaper one.

If you are interested in doing either of these tasks please email me ( andy at oryxdigital.com ) before the end of Friday 26th August with subject “programming work” and a brief outline of:

  • Which of the 2 tasks you are interested in.
  • Your relevant experience. Ideally including details of related projects completed.
  • Your daily rate in Pounds Sterlings or US dollars.

I will send detailed specs to a shortlist of the best candidates. The work will be awarded on the basis of fixed price bids against the spec. Please don’t apply unless you have relevant experience – if I wanted a programmer without experience in these areas I could do it myself. ;0)

C++ for the next decade

C++

Although some people regard C++ as the COBOL of the 21st century, it remains a force to be reckoned with in commercial development. For example it is currently ranked fourth in the language related tags on stackoverflow.com (despite the apparent biases of Stackoverflow owners Jeff Atwood and Joel Spolsky towards web and .Net oriented languages):

Rank Language Tagged questions
1 C# 4681
2 Java 2903
3 ASP.Net 2334
4 C++ 2040
5 Javascript 1677
6 PHP 1505
7 Python 1397
8 C 851
9 Ruby 719
10 VB.Net 548

C++ has been one of the top commercial languages for a long time. But the world of computer software and hardware is changing fast and languages have to evolve to stay relevant. The first major revision to the C++ standard in a decade, known as C++ 0x, is expected be finalised in 2009 (otherwise the x will have to be hex). The draft standard includes lots of additions to the language and standard libraries, including: lambdas; closures; static (compile time) asserts; concepts; automatic types; variadic templates; a regular expressions library and improved threading support. Automatic garbage collection is notable by its absence.

For working C++ developers the new standard only really becomes important when it becomes available in mainstream compilers such as Visual C++ and Gnu C++. As Gnu C++ already has experimental support for C++ 0x and Microsoft released a preview of Visual Studio 2010 at PDC last month with support for some of new features it might be a good time to start paying attention to the new standard. You don’t want to look like an idiot next time one your colleagues starts talking about ‘lambdas’, do you?

I illustrate a few of the new features below. I have done this mainly as a way of understanding them better myself, not because I claim any sort of expertise on the new standard.

Lambdas and closures

A ‘lambda’ is an unnamed function, for example:

std::vector<int> values = getValues();
std::for_each( values.begin(), values.end(), [](int n) { cout << n << std::endl; } );

Lambdas can reference in-scope variables, for example:

std::vector<int> values = getValues();
int total = 0;
std::for_each( values.begin(), values.end(), [&total](int n) { total += n } );

This is known as a ‘closure’. Of course, all of this can be done with standard function calls, but lambdas are undoubtedly more compact and elegant. I am not convinced that they will make code any clearer or easier to debug or maintain however.

Automatic types

Automatic typing allows the compiler to infer a type. For example:

std::vector<int> values = getValues();
for ( std::vector<int>::const_iterator it = values.begin(); it != values.end(); ++it ) { f( it ); }

Can be re-written as:

auto values = getValues();
for ( auto it = values.begin(); it != values.end(); ++it ) { f( it ); }

Automatic types seem like an excellent way to let the compiler take some of the drudgery out of programming.

Concepts

Template error messages have improved over the years, but they can still be obscure. A ‘concept’ is a way to clearly define what types a templated class or function will accept. For example:

template<typename T> requires LessThanComparable<T>
const T& min(const T &x, const T &y)
{
return y < x ? y : x;
}

Specifies that min() will only accept types that support the concept LessThanComparable.  LessThanComparable can then be defined so that the type must support the < operator:

auto concept LessThanComparable<typename T>
{
bool operator<(T, T);
}

Hopefully concepts will allow better defined template interfaces and clearer error messages.

Concurrency

The current C++ standard makes no real allowances for concurrency. This is a major problem in a world where multi-core CPUs are standard. The new standard will introduce a memory model that supports threading and a standard threading library.

Summary

C++ has many strengths. It scores quite highly on performance, expressiveness and portability, has an extensive tool and library ‘ecosystem’ and a proven track record in large scale system development. But it is also a sprawling and complex language, hobbled by many shortcomings inherited from its progenitor C (a language dating back to the early seventies). It isn’t clear to me whether the new standard will add enough features to keep C++ competitive as a commercial language for another decade. Or whether C++ will be regarded as a legacy language, too bloated and complex to attract new developers given the choice of simpler and more elegant languages. Time will tell.

Further reading:

C++ 0x article on wikipedia

CoverageValidator v3

The nice folk at Software Verification have done a major new release of Coverage Validator, and the new version fixes many of the issues I noted in a previous post. In particular:

  • The instrumentation can use breakpoint functionality to get better line coverage on builds with debug information enabled.
  • Previous sessions can be automatically merged into new sessions.
  • The default colour scheme has been toned down.
  • The flashing that happened when you resized the source window has gone.
  • It is now possible to mark sections of code not to be instrumented. I haven’t had time to try this yet, as it was only introduced in v3.0.4. But it should be very useful as currently I have a lot of defensive code that should never be reached (see below). Instrumenting this code skews the coverage stats and makes it harder to spot lines that should have been executed, but weren’t.

There are still a few issues:

  • I had problems trying to instrument release versions of my code.
  • It still fails to instrument some lines (but not many).
  • I had a couple of crashes during testing that don’t seem to have been caused by my software (although I can’t prove that).

But the technical support has been very responsive and new versions are released fairly frequently. Overall version 3 is a major improvement to a very useful tool. Certainly it helped me find a few bugs during the testing of version 4 of Perfect Table Plan on Windows. I just wish there was something comparable for MacOSX.