This is a potentially dangerous question because interdisciplinary questions and answers will be biased, but I'll have a stab at it anyway. All in good spirit!
So, here we go. I'm writing a major editing mode for Emacs for the language that it has almost no support for yet. And I'm at the point, where I have to decide on a way to generate project files. Below is the syllabus of the task ahead:
The templates have to represent project directory tree, not only single files.
The resulting files are of various formats, potentially including SGML-like languages, but not limited to this variety. They also have to generate C-like source code and, eLisp source code and plain text files, like README, for example.
The templates must be processed in a batch upon user-initiated action (as in user wants to create a project - several files must be created in the user-appointed directory). It may be beneficial to have an ability to supervise the creation, but this is less important then the ability to run the process entirely automatically.
Bonus features:
The template language has already a user base (with a potential of reuse of existing templates).
The templates can be used for code snippets (contain blanks which are filled interactively once the user invokes code-generating routine while editing the file).
Obvious things like cross-platform-ness, ease of use both through graphical interface and command line.
I made a research, but I won't share my results (yet) so I won't bias the answers. The problem with answering this question is not that the answer is hard to find, but that it is hard to chose one from many.
I'm developing a system based on Mustache for exactly the use case that you've described. The template language itself is a very simple extension of Mustache called Groome.
I also released a command-line tool called Molt that renders Groome templates. I'd be curious to know if it does everything that you need. I'm still adding features to the tool and haven't yet announced it. Thanks.
I went to solve a similar problem several years aback, where I wanted to use Emacs to generate code out of a UML diagram (cogre), and also generate Makefiles from project specifications. I first tried to use Tempo, but when I tried to get the templates to nest, I ran into problems. I also looked into skeleton, but that didn't quite fit the plan either.
I ended up using Google Templates for a little bit, and liked the syntax, and developed SRecode instead, and just borrowed the good bits from Google templates. SRecode was written specifically for machine-generated code. The interaction for template insertion (aka - what tempo was written for) isn't first class in SRecode. For generating code from a data structure, however, it is very robust, and has a lot of features, and automatically filled variables. It works closely with your major mode, and allows many nested templates, with control over the nested dictionary values. There is a subsystem that will use Semantic tags and generate code from them for a couple languages. That means you can parse code in one language with Semantic, and generate code in another language with SReocde using those tags. Nifty! Many parts of CEDET Reference manuals were built that way.
The templates themselves allow looping, if statements, and include statements. There are a couple examples in SRecode for making an 'application', such as the comment writer, and EDE uses it to create Makefiles, which is almost exactly what you are trying to do.
Another option is Generator, which offers “language-agnostic project bootstrapping with an emphasis on simplicity”. Installation requires Node.js and npm.
Generator’s emphasis on simplicity means it is very easy to learn how to make a template. Generator also saves you from having to reference templates by file paths – it looks for templates in ~/.generator.
However, there is no way to write README or LICENSE files for the template itself without those files being copied to the generated project. Also, post-generation commands written in the Makefile will be copied to the generated Makefile, even after they are no longer of use. Finally, the ad-hoc templating language doesn’t provide a way to escape its __lowercasevariables__ – though I can’t think of a language where that limitation would be a problem.
Related
I am looking at various STL headers provided with compilers and I cant imagine the developers actually writing all this code by hand.
All the macros and the weird names of varaibles and classes - they would have to remember all of them! Seems error prone to me.
Are parts of the headers result of some text preprocessing or generation?
I've maintained Visual Studio's implementation of the C++ Standard Library for 7 years (VC's STL was written by and licensed from P.J. Plauger of Dinkumware back in the mid-90s, and I work with PJP to pick up new features and maintenance bugfixes), and I can tell you that I do all of my editing "by hand" in a plain text editor. None of the STL's headers or sources are automatically generated (although Dinkumware's master sources, which I have never seen, go through automated filtering in order to produce customized drops for Microsoft), and the stuff that's checked into source control is shipped directly to users without any further modification (now, that is; previously we ran them through a filtering step that caused lots of headaches). I am notorious for not using IDEs/autocomplete, although I do use Source Insight to browse the codebase (especially the underlying CRT whose guts I am less familiar with), and I extensively rely on grep. (And of course I use diff tools; my favorite is an internal tool named "odd".) I do engage in very very careful cut-and-paste editing, but for the opposite reason as novices; I do this when I understand the structure of code completely, and I wish to exactly replicate parts of it without accidentally leaving things out. (For example, different containers need very similar machinery to deal with allocators; it should probably be centralized, but in the meantime when I need to fix basic_string I'll verify that vector is correct and then copy its machinery.) I've generated code perhaps twice - once when stamping out the C++14 transparent operator functors that I designed (plus<>, multiplies<>, greater<>, etc. are highly repetitive), and again when implementing/proposing variable templates for type traits (recently voted into the Library Fundamentals Technical Specification, probably destined for C++17). IIRC, I wrote an actual program for the operator functors, while I used sed for the variable templates. The plain text editor that I use (Metapad) has search-and-replace capabilities that are quite useful although weaker than outright regexes; I need stronger tools if I want to replicate chunks of text (e.g. is_same_v = is_same< T >::value).
How do STL maintainers remember all this stuff? It's a full time job. And of course, we're constantly consulting the Standard/Working Paper for the required interfaces and behavior of code. (I recently discovered that I can, with great difficulty, enumerate all 50 US states from memory, but I would surely be unable to enumerate all STL algorithms from memory. However, I have memorized the longest name, as a useless bit of trivia. :->)
The looks of it are designed to be weird in some sense. The standard library and the code in there needs to avoid conflicts with names used in user programs, including macros and there are almost no restrictions as to what can be in a user program.
They are most probably hand written, and as others have mentioned, if you spend some time looking at them you will figure out what the coding conventions are, how variables are named and so on. One of the few restrictions include that user code cannot use identifiers starting with _ followed by a capital letter or __ (two consecutive underscores), so you will find many names in the standard headers that look like _M_xxx or __yyy and it might surprise at first, but after some time you just ignore the prefix...
Issue
I have recently found myself working with a large, unfamiliar, multi-department, C++ codebase in need of better organization. I would like to discover a way to map which symbols are used by which source files for any given header. This is in the hope that if only one department uses a given function, then it can be moved out of the shared area and into that department's area.
Attempts
My first thoughts were to use the symbol table: ie. compile the project and dump the symbols for each object file. From there I figured I could simply write a script to check if the symbols from my header file were used. While this approach seems viable, it would require me to create a list of symbols I am looking for from the headers. With my limited knowledge, I am unsure of how to automate such a process, and with hundreds of headers files to test, doing it manually is out of the question.
Questions
Is my approach valid? If so..
What can I use to generate the symbol names from my header file?
If not..
What else can I do?
Additionally, while I am using Linux, most of the development teams work in Windows only environments. What utilities could I use on both platforms?
Any and all help is greatly appreciated.
When I need to clean up APIs I sometimes use information from callcatcher. It basically builds a database of all symbols while compiling and allows you to determine what symbols are used in some build product.
I sometimes also use DXR (code on github, an example installation) to browse what code defined where is used how. In contrast to callcatcher with DXR you can drill down to much finer detail. Setting up DXR is pretty heavy duty, but might be worth it if you have enough code to work with.
On the other side of the spectrum there are tools like cscope. Even though it doesn't work super nicely with C++ code it is still very useful. If you deal with more than a couple 100kloc you will quickly feel limited though.
If I had to pick only one of these tools and would be working on a large code base (>1Mloc) I would definitely pick DXR.
You can get a reasonable start on the information that you've described by using doxygen.
Even for source that doesn't contain the doxygen formatted comments the documentation created can contain a list of places (ie. source files) where a particular symbol is used.
And, as doxygen can be used to generate html documentation, navigating through your source tree becomes trivial. It's can be even better if you enable the dot functionality to generate relationship diagrams for the classes in your source tree.
very old-school, simple, and possibly unix only, but are you aware of etags? there's also gnu global which i think is similar.
the gnu global link refers to the "comparison with similar tools" discussion here which might also be useful.
Rationale: In my day-to-day C++ code development, I frequently need to
answer basic questions such as who calls what in a very large C++ code
base that is frequently changing. But, I also need to have some
automated way to exactly identify what the code is doing around a
particular area of code. "grep" tools such as Cscope are useful (and
I use them heavily already), but are not C++-language-aware: They
don't give any way to identify the types and kinds of lexical
environment of a given use of a type or function a such way that is
conducive to automation (even if said automation is limited to
"read-only" operations such as code browsing and navigation, but I'm
asking for much more than that below).
Question: Does there exist already an open-source C/C++-based library
(native, not managed, not Microsoft- or Linux-specific) that can
statically scan or analyze a large tree of C++ code, and can produce
result sets that answer detailed questions such as:
What functions are called by some supplied function?
What functions make use of this supplied type?
Ditto the above questions if C++ classes or class templates are involved.
The result set should provide some sort of "handle". I should be able
to feed that handle back to the library to perform the following types
of introspection:
What is the byte offset into the file where the reference was made?
What is the reference into the abstract syntax tree (AST) of that
reference, so that I can inspect surrounding code constructs? And
each AST entity would also have file path, byte-offset, and
type-info data associated with it, so that I could recursively walk
up the graph of callers or referrers to do useful operations.
The answer should meet the following requirements:
API: The API exposed must be one of the following:
C or C++ and probably is "C handle" or C++-class-instance-based
(and if it is, must be generic C o C++ code and not Microsoft- or
Linux-specific code constructs unless it is to meet specifics of
the given platform), or
Command-line standard input and standard output based.
C++ aware: Is not limited to C code, but understands C++ language
constructs in minute detail including awareness of inter-class
inheritance relationships and C++ templates.
Fast: Should scan large code bases significantly faster than
compiling the entire code base from scratch. This probably needs to
be relaxed, but only if Incremental result retrieval and Resilient
to small code changes requirements are fully met below.
Provide Result counts: I should be able to ask "How many results
would you provide to some request (and no don't send me all of the
results)?" that responds on the order of less than 3 seconds versus
having to retrieve all results for any given question. If it takes
too long to get that answer, then wastes development time. This is
coupled with the next requirement.
Incremental result retrieval: I should be able to then ask "Give me
just the next N results of this request", and then a handle to the
result set so that I can ask the question repeatedly, thus
incrementally pulling out the results in stages. This means I
should not have to wait for the entire result set before seeing
some subset of all of the results. And that I can cancel the
operation safely if I have seen enough results. Reason: I need to
answer the question: "What is the build or development impact of
changing some particular function signature?"
Resilient to small code changes: If I change a header or source
file, I should not have to wait for the entire code base to be
rescanned, but only that header or source file
rescanned. Rescanning should be quick. E.g., don't do what cscope
requires you to do, which is to rescan the entire code base for
small changes. It is understood that if you change a header, then
scanning can take longer since other files that include that header
would have to be rescanned.
IDE Agnostic: Is text editor agnostic (don't make me use a specific
text editor; I've made my choice already, thank you!)
Platform Agnostic: Is platform-agnostic (don't make me only use it
on Linux or only on Windows, as I have to use both of those
platforms in my daily grind, but I need the tool to be useful on
both as I have code sandboxes on both platforms).
Non-binary: Should not cost me anything other than time to download
and compile the library and all of its dependencies.
Not trial-ware.
Actively Supported: It is likely that sending help requests to mailing lists
or associated forums is likely to get a response in less than 2
days.
Network agnostic: Databases the library builds should be able to be used directly on
a network from 32-bit and 64-bit systems, both Linux and Windows
interchangeably, at the same time, and do not embed hardcoded paths
to filesystems that would otherwise "root" the database to a
particular network.
Build environment agnostic: Does not require intimate knowledge of my build environment, with
the notable exception of possibly requiring knowledge of compiler
supplied CPP macro definitions (e.g. -Dmacro=value).
I would say that CLang Index is a close fit. However I don't think that it stores data in a database.
Anyway the CLang framework offer what you actually need to build a tool tailored to your needs, if only because of its C, C++ and Objective-C parsing / indexing capabitilies. And since it's provided as a set of reusable libraries... it was crafted for being developed on!
I have to admit that I haven't used either because I work with a lot of Microsoft-specific code that uses Microsoft compiler extensions that i don't expect them to understand, but the two open source analyzers I'm aware of are Mozilla Pork and the Clang Analyzer.
If you are looking for results of code analysis (metrics, graphs, ...) why not use a tool (instead of API) to do that? If you can, I suggest you to take a look at Understand.
It's not free (there's a trial version) but I found it very useful.
Maybe Doxygen with GraphViz could be the answer of some of your constraints but not all,for example the analysis of Doxygen is not incremental.
I'm just starting to explore C++, so forgive the newbiness of this question. I also beg your indulgence on how open ended this question is. I think it could be broken down, but I think that this information belongs in the same place.
(FYI -- I am working predominantly with the QT SDK and mingw32-make right now and I seem to have configured them correctly for my machine.)
I knew that there was a lot in the language which is compiler-driven -- I've heard about pre-compiler directives, but it seems like someone would be able to write books the different C++ compilers and their respective parameters. In addition, there are commands which apparently precede make (like qmake, for example (is this something only in QT)).
I would like to know if there is any place which gives me an overview of what compilers are out there, and what their different options are. I'd also like to know how each of them views Makefiles (it seems that there is a difference in syntax between them?).
If there is no website regarding, "Everything you need to know about C++ compilers but were afraid to ask," what would be the best way to go about learning the answers to these questions?
Concerning the "numerous options of the various compilers"
A piece of good news: you needn't worry about the detail of most of these options. You will, in due time, delve into this, only for the very compiler you use, and maybe only for the options that pertain to a particular set of features. But as a novice, generally trust the default options or the ones supplied with the make files.
The broad categories of these features (and I may be missing a few) are:
pre-processor defines (now, you may need a few of these)
code generation (target CPU, FPU usage...)
optimization (hints for the compiler to favor speed over size and such)
inclusion of debug info (which is extra data left in the object/binary and which enables the debugger to know where each line of code starts, what the variables names are etc.)
directives for the linker
output type (exe, library, memory maps...)
C/C++ language compliance and warnings (compatibility with previous version of the compiler, compliance to current and past C Standards, warning about common possible bug-indicative patterns...)
compile-time verbosity and help
Concerning an inventory of compilers with their options and features
I know of no such list but I'm sure it probably exists on the web. However, suggest that, as a novice you worry little about these "details", and use whatever free compiler you can find (gcc certainly a great choice), and build experience with the language and the build process. C professionals may likely argue, with good reason and at length on the merits of various compilers and associated runtine etc., but for generic purposes -and then some- the free stuff is all that is needed.
Concerning the build process
The most trivial applications, such these made of a single unit of compilation (read a single C/C++ source file), can be built with a simple batch file where the various compiler and linker options are hardcoded, and where the name of file is specified on the command line.
For all other cases, it is very important to codify the build process so that it can be done
a) automatically and
b) reliably, i.e. with repeatability.
The "recipe" associated with this build process is often encapsulated in a make file or as the complexity grows, possibly several make files, possibly "bundled together in a script/bat file.
This (make file syntax) you need to get familiar with, even if you use alternatives to make/nmake, such as Apache Ant; the reason is that many (most?) source code packages include a make file.
In a nutshell, make files are text files and they allow defining targets, and the associated command to build a target. Each target is associated with its dependencies, which allows the make logic to decide what targets are out of date and should be rebuilt, and, before rebuilding them, what possibly dependencies should also be rebuilt. That way, when you modify say an include file (and if the make file is properly configured) any c file that used this header will be recompiled and any binary which links with the corresponding obj file will be rebuilt as well. make also include options to force all targets to be rebuilt, and this is sometimes handy to be sure that you truly have a current built (for example in the case some dependencies of a given object are not declared in the make).
On the Pre-processor:
The pre-processor is the first step toward compiling, although it is technically not part of the compilation. The purposes of this step are:
to remove any comment, and extraneous whitespace
to substitute any macro reference with the relevant C/C++ syntax. Some macros for example are used to define constant values such as say some email address used in the program; during per-processing any reference to this constant value (btw by convention such constants are named with ALL_CAPS_AND_UNDERSCORES) is replace by the actual C string literal containing the email address.
to exclude all conditional compiling branches that are not relevant (the #IFDEF and the like)
What's important to know about the pre-processor is that the pre-processor directive are NOT part of the C-Language proper, and they serve several important functions such as the conditional compiling mentionned earlier (used for example to have multiple versions of the program, say for different Operating Systems, or indeed for different compilers)
Taking it from there...
After this manifesto of mine... I encourage to read but little more, and to dive into programming and building binaries. It is a very good idea to try and get a broad picture of the framework etc. but this can be overdone, a bit akin to the exchange student who stays in his/her room reading the Webster dictionary to be "prepared" for meeting native speakers, rather than just "doing it!".
Ideally you shouldn't need to care what C++ compiler you are using. The compatability to the standard has got much better in recent years (even from microsoft)
Compiler flags obviously differ but the same features are generally available, it's just a differently named option to eg. set warning level on GCC and ms-cl
The build system is indepenant of the compiler, you can use any make with any compiler.
That is a lot of questions in one.
C++ compilers are a lot like hammers: They come in all sizes and shapes, with different abilities and features, intended for different types of users, and at different price points; ultimately they all are for doing the same basic task as the others.
Some are intended for highly specialized applications, like high-performance graphics, and have numerous extensions and libraries to assist the engineer with those types of problems. Others are meant for general purpose use, and aren't necessarily always the greatest for extreme work.
The technique for using each type of hammer varies from model to model—and version to version—but they all have a lot in common. The macro preprocessor is a standard part of C and C++ compilers.
A brief comparison of many C++ compilers is here. Also check out the list of C compilers, since many programs don't use any C++ features and can be compiled by ordinary C.
C++ compilers don't "view" makefiles. The rules of a makefile may invoke a C++ compiler, but also may "compile" assembly language modules (assembling), process other languages, build libraries, link modules, and/or post-process object modules. Makefiles often contain rules for cleaning up intermediate files, establishing debug environments, obtaining source code, etc., etc. Compilation is one link in a long chain of steps to develop software.
Also, many development environments abstract the makefile into a "project file" which is used by an integrated development environment (IDE) in an attempt to simplify or automate many programming tasks. See a comparison here.
As for learning: choose a specific problem to solve and dive in. The target platform (Linux/Windows/etc.) and problem space will narrow the choices pretty well. Which you choose is often linked to other considerations, such as working for a particular company, or being part of a team. C++ has something like 95% commonality among all its flavors. Learn any one of them well, and learning the next is a piece of cake.
When you get a third-party library (c, c++), open-source (LGPL say), that does not have good documentation, what is the best way to go about understanding it to be able to integrate into your application?
The library usually has some example programs and I end up walking through the code using gdb. Any other suggestions/best-practicies?
For an example, I just picked one from sourceforge.net, but it's just a broad engineering/programming question:
http://sourceforge.net/projects/aftp/
I frequently use a couple of tools to help me with this:
GNU Global. It generates cross-referencing databases and can produce hyperlinked HTML from source code. Clicking function calls will take you to their definitions, and you can see lists of all references to a function. Only works for C and perhaps C++.
Doxygen. It generates documentation from Javadoc-style comments. If you tell it to generate documentation for undocumented methods, it will give you nice summaries. It can also produce hyperlinked source code listings (and can link into the listings provided by htags).
These two tools, along with just reading code in Emacs and doing some searches with recursive grep, are how I do most of my source reverse-engineering.
One of the better ways to understand it is to attempt to document it yourself. By going and trying to document it yourself, it forces you to really dive in and test and test and test and make sure you know what each statement is doing at what times. Then you can really start to understand what the previous developer may have been thinking (or not thinking for that matter).
Great question. I think that this should be addressed thoroughly, so I'm going to try to make my answer as thorough as possible.
One thing that I do when approaching large projects that I've either inherited or contributing to is automatically generate their sources, UML diagrams, and anything that can ease the various amounts of A.D.D. encountered when learning a new project:)
I believe someone here already mentioned Doxygen, that's a great tool! You should look into it and write a small bash script that will automatically generate sources for the application you're developing in some tree structure you've setup.
One thing that I've haven't seen people mention is BOUML! It's fantastic and free! It automatically generates reverse UML diagrams from existing sources and it supports a variety of languages. I use this as a way to really capture the big picture of what's going on in terms of architecture and design before I start reading code.
If you've got the money to spare, look into Understand for %language-here%. It's absolutely great and has helped me in many ways when inheriting legacy code.
EDIT:
Try out ack (betterthangrep.com), it is a pretty convenient script for searching source trees:)
Familiarize yourself with the information available in the headers. The functions you call will be declared there. Then try to identify the valid arguments and pre-/post-conditions of the functions, as those are your primary guidance (even if they are not documented!). The example programs are your next bet.
If you have code completion/intellisense I like opening up the library and going '.' or 'namespace::' and seeing what comes up. I always find it helpful, you can navigate through the objects/namespaces and see what functionality they have. This is of course assuming its an OOP library with relatively good naming of functions/objects.
There really isn't a silver bullet other than just rolling up your sleeves and digging into the code.
This is where we earn our money.
Three things;
(1) try to run the test or example apps available, set low debug levels, and walk through logs.
(2) use source navigator tool / cscope ( available both on windows and linux) and browse the code to understand the flow.
(3) also in parallel use gdb to walk into code while running test/example apps.