Qt's resource system lets you build an executable that has resources (.qml's, images...) embedded inside it. I'd like to load the files from the filesystem instead, and ship them alongside my executable. Is this a technique supported by Qt? Any gotchas? Any advantages to one way or the other?
Qt doesn't limit you in what you can do here. It's your choice. Qt's resource system is there if you want it, it's not forced down your throat. Not using it doesn't make you automatically wrong.
If you want to deploy files along with your application, go for it - if it makes sense for your particular application.
My personal preference for small (<0.25GB) applications is for a nice monolithic portable executable on Windows, with everything inside, that you don't have to install if you don't wish - mimicking how an app bundle would be on OS X.
The portability helps, as does the slightly stronger locality of reference: most filesystems will attempt to keep a file's blocks together a bit harder than they do for files that merely are in the same folder.
If there's any utility in power users tweaking the contents of the deployed files, then certainly using the files over using resources has advantages. You could also use the resource system as a fallback for files that are missing - that way a user could provide a replacement file optionally, if it's something you could use.
To make it short: If it is applicable for your application and 'business model' it is ok.
Besides being supported by Qt using QFile (for example), Qt's resource system has some advantages:
compression (ZIP)
simple usage in the application
no care about missing files (typically)
If you mind adding all resources to the executable will not work for you and you want to seperate them, look at the option of seperate (binary) resource files with Qt.
I'm frustrated by the lack of flexibility in the Visual Studio project/solution, but I realized that now that it uses MSBUILD it might be quite powerful but just doesn't expose that to the IDE. So I took a look at MSBUILD docs and don't know where to start! I wish there was a Nutshell book for that. Is there any good tutorial someone could point me to?
More specifically, here is the kinds of things I want to do:
Run a utility pre-processor to generate .CPP and .H files, which are then used by a regular C++ project. There are multiple inputs (to figure dependencies of; specifically should know if a normal .h file it uses has changed) and multiple outputs (at least one .cpp and one .h file) that are used as files in another project.
FWIW, the most complex case involves using Qt in a "normal" C++ project that can be built using VS Express 2010 or MSBUILD directly from a script on a server. Since that is a common library, there might be some guides or whatever to help? Note that a VS plug-in is not useful for the building stage, but could be used to initially generate project files that then rely only on MSBUILD and stuff included with the source code.
Would somebody please point me in the right direction?
--John
It gets worse from there, but that's my first goal.
I found the kind of information I was looking for in a book MSBuild Trickery: 99 Ways to Bend the Build Engine to Your Will by Brian Kretzler.
In the first 18 pages I found a few key pieces of information that, along with the on-line documentations I've already gone through, helps clear things up enough to try tackling my project. Details of interest include the processing order of how MSBuild reads and operates on the things in the file, quick points on when wildcard in items are expanded and how to handle generated files, and how to see what's happening in some practical cases or even step in the debugger.
FWIW, I managed to attack my problem without using the murky ".targets"/rules files that I have yet to understand, but only using better documented/exampled features (in particular, a Target that has wildcard items doesn't care that the file name extension is not in any ".target"; is simple enough to copy from example and allows the files to be seen in the IDE Project and added to the list using the IDE; again, the FileExtension there just works OK.)
I'm working on some general purpose math libraries that I will want to use in multiple projects. Obviously, it makes sense for all the project to reference the same code files so if I fix something it affects all projects.
One way to do this would be to simply have them all use an INCLUDEPATH and DEPENDPATH that points to the same directory of code files.
But I was reading this: http://qt-project.org/wiki/IncludingProFiles
And I'm wondering if it is better to create a .pri Qt project for purposes of inclusion only. Would this be better? Do you have to then manually change the extension from .pro to .pri?
What's the best setup for sharing code between projects?
Obviously you know the way of including them with INCLUDEPATH and DEPENDPATH, which is fairly easy to setup but a bit annoying. Using a pri file does alleviate some of the headaches, and it makes it easier to add them into a new project as you go along with any additional customisation you like to have on projects. Or if you're working on a large multi-application project and need to keep similar build settings.
The third option is building them as a library file and just including them, the same as you would any library. Trickier to setup initially than just using a pri or the include directives, but it does mean the code is kept as it's own separate unit.
If it's a small amount of code, but you plan on using it often I'd use a pri, if it's a reasonably large amount of code I'd go for library, and if you only plan on using it rarely I'd use the include directives.
The best way is to create a versioned repo of the source in e.g. git. Make it possible to build a versioned SDK (containing lib*.so/lib*.a and *.h) from the source to share. Most sucessful projects grow over time and then this investment will pay off. Learning how to do this once you can do re-use easier in the future across several platforms. Re-use is very important.
i have to create a dynamically linked library in zOS . What are the options to be passed to the compiler.
Also, how to check if a library in zOS is dynamically linked[dependent] on other libraries.
we have ldd in linux, which shows this linkage. Do we have a 'ldd' equivalent in zOS land?
You don't say it directly, but I assume you mean a C/C++ DLL. You can do shared libraries in other languages as well (even assembler), but the steps would be different.
First, you need to decide what you want to export. A lot of the IBM examples use the compiler EXPORTALL directive, but be aware this can lead to very slow executables, depending on your coding style. If you don't do EXPORTALL, you'll need #pragma export for anything (code or data) you want to export. Don't forget you can export data (variables) as well as executable functions...sometimes you'll need this to share data with DLL functions.
Then, you need to set your compile options on both client (caller) and DLL to use the DLL linkage...this is the -Wc,DLL compile option and when enabled, it generates extra logic in your program to load and manage the DLL. It's a good idea to also include #pragma csect for your exported functions if you think you'll ever have the need to update the DLL without replacing it entirely.
When you link your DLL, be sure to specify the -Wl,DLL option (there are lots of ways...this part is different if you link in batch - I'm assuming you're building in a make file of some sort). The link will generate the actual DLL, as well as a "side deck" containing "IMPORT" statements for all of your exported functions. You'll need these to link any of the client-side programs that you expect to call the DLL. For example, if your imports are in a file called AAA.x, c89 -Wc,DLL myapp.c AAA.x would compile the calling code, with awareness that functions in AAA.x are off in some sort of DLL.
To your point about DLLs calling other DLLs, don't forget that a DLL can both "serve" and "consume" functions...by including the side deck for functions in other DLLs, you can have a DLL that provides some functions while calling other DLLs to access others.
The actual DLL itself can be in several places depending on the nature of your app. If you're UNIX Services friendly, it's just an executable in LIBPATH. It can also be STEPLIB, LNKLST, LPA and so forth.
If you need to, you can access your DLLs explicitly at runtime using dlopen(), dlsym() and so forth. Generally, this lets you control exactly which DLL you're using (sometimes handy if the user can provide one himself), and it gives you what amounts to function pointers that are resolved within the DLL.
There are some other basic things to consider when linking, such as ensuring that your code is reentrant. Most of these are spelled out in the IBM documentation, and if you build with things like "c89" (or equivalent), the correct options are usually setup for you automatically (in fact, to get a good idea of what's going on, turn on the verbose output and see all the parameters for yourself).
If you need to build up a cross reference of what calls what, the UNIX Services "nm" command can give you that information. If you produce detailed link-edit listings, all the data is in there too when you're building your DLLs.
Good luck!
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A few years ago, I read the Recursive Make Considered Harmful paper and implemented the idea in my own build process. Recently, I read another article with ideas about how to implement non-recursive make. So I have a few data points that non-recursive make works for at least a few projects.
But I'm curious about the experiences of others. Have you tried non-recursive make? Did it make things better or worse? Was it worth the time?
We use a non-recursive GNU Make system in the company I work for. It's based on Miller's paper and especially the "Implementing non-recursive make" link you gave. We've managed to refine Bergen's code into a system where there's no boiler plate at all in subdirectory makefiles. By and large, it works fine, and is much better than our previous system (a recursive thing done with GNU Automake).
We support all the "major" operating systems out there (commercially): AIX, HP-UX, Linux, OS X, Solaris, Windows, even the AS/400 mainframe. We compile the same code for all of these systems, with the platform dependent parts isolated into libraries.
There's more than two million lines of C code in our tree in about 2000 subdirectories and 20000 files. We seriously considered using SCons, but just couldn't make it work fast enough. On the slower systems, Python would use a couple of dozen seconds just parsing in the SCons files where GNU Make did the same thing in about one second. This was about three years ago, so things may have changed since then. Note that we usually keep the source code on an NFS/CIFS share and build the same code on multiple platforms. This means it's even slower for the build tool to scan the source tree for changes.
Our non-recursive GNU Make system is not without problems. Here are some of biggest hurdles you can expect to run into:
Making it portable, especially to Windows, is a lot of work.
While GNU Make is almost a usable functional programming language, it's not suitable for programming in the large. In particular, there are no namespaces, modules, or anything like that to help you isolate pieces from each other. This can cause problems, although not as much as you might think.
The major wins over our old recursive makefile system are:
It's fast. It takes about two seconds to check the entire tree (2k directories, 20k files) and either decide it's up to date or start compiling. The old recursive thing would take more than a minute to do nothing.
It handles dependencies correctly. Our old system relied on the order subdirectories were built etc. Just like you'd expect from reading Miller's paper, treating the whole tree as a single entity is really the right way to tackle this problem.
It's portable to all of our supported systems, after all the hard work we've poured into it. It's pretty cool.
The abstraction system allows us to write very concise makefiles. A typical subdirectory which defines just a library is just two lines. One line gives the name of the library and the other lists the libraries this one depends on.
Regarding the last item in the above list. We ended up implementing a sort of macro expansion facility within the build system. Subdirectory makefiles list programs, subdirectories, libraries, and other common things in variables like PROGRAMS, SUBDIRS, LIBS. Then each of these are expanded into "real" GNU Make rules. This allows us to avoid much of the namespace problems. For example, in our system it's fine to have multiple source files with the same name, no problem there.
In any case, this ended up being a lot of work. If you can get SCons or similar working for your code, I'd advice you look at that first.
After reading the RMCH paper, I set out with the goal of writing a proper non-recursive Makefile for a small project I was working on at the time. After I finished, I realized that it should be possible to create a generic Makefile "framework" which can be used to very simply and concisely tell make what final targets you would like to build, what kind of targets they are (e.g. libraries or executables) and what source files should be compiled to make them.
After a few iterations I eventually created just that: a single boilerplate Makefile of about 150 lines of GNU Make syntax that never needs any modification -- it just works for any kind of project I care to use it on, and is flexible enough to build multiple targets of varying types with enough granularity to specify exact compile flags for each source file (if I want) and precise linker flags for each executable. For each project, all I need to do is supply it with small, separate Makefiles that contain bits similar to this:
TARGET := foo
TGT_LDLIBS := -lbar
SOURCES := foo.c baz.cpp
SRC_CFLAGS := -std=c99
SRC_CXXFLAGS := -fstrict-aliasing
SRC_INCDIRS := inc /usr/local/include/bar
A project Makefile such as the above would do exactly what you'd expect: build an executable named "foo", compiling foo.c (with CFLAGS=-std=c99) and baz.cpp (with CXXFLAGS=-fstrict-aliasing) and adding "./inc" and "/usr/local/include/bar" to the #include search path, with final linking including the "libbar" library. It would also notice that there is a C++ source file and know to use the C++ linker instead of the C linker. The framework allows me to specify a lot more than what is shown here in this simple example.
The boilerplate Makefile does all the rule building and automatic dependency generation required to build the specified targets. All build-generated files are placed in a separate output directory hierarchy, so they're not intermingled with source files (and this is done without use of VPATH so there's no problem with having multiple source files that have the same name).
I've now (re)used this same Makefile on at least two dozen different projects that I've worked on. Some of the things I like best about this system (aside from how easy it is to create a proper Makefile for any new project) are:
It's fast. It can virtually instantly tell if anything is out-of-date.
100% reliable dependencies. There is zero chance that parallel builds will mysteriously break, and it always builds exactly the minimum required to bring everything back up-to-date.
I will never need to rewrite a complete makefile again :D
Finally I'd just mention that, with the problems inherent in recursive make, I don't think it would have been possible for me to pull this off. I'd probably have been doomed to rewriting flawed makefiles over and over again, trying in vain to create one that actually worked properly.
Let me stress one argument of Miller's paper: When you start to manually resolve dependency relationships between different modules and have a hard time to ensure the build order, you are effectively reimplementing the logic the build system was made to solve in the first place. Constructing reliable recursive make build systems is very hard. Real life projects have many interdependent parts whose build order is non-trivial to figure out and thus, this task should be left to the build system. However, it can only resolve that problem if it has global knowledge of the system.
Furthermore, recursive make build-systems are prone to fall apart when building concurrently on multiple processors/cores. While these build systems may seem to work reliably on a single processor, many missing dependencies go undetected until you start to build your project in parallel. I've worked with a recursive make build system which worked on up to four processors, but suddenly crashed on a machine with two quad-cores. Then I was facing another problem: These concurrency issues are next to impossible to debug and I ended up drawing a flow-chart of the whole system to figure out what went wrong.
To come back to your question, I find it hard to think of good reasons why one wants to use recursive make. The runtime performance of non-recursive GNU Make build systems is hard to beat and, quite the contrary, many recursive make systems have serious performance problems (weak parallel build support is again a part of the problem). There is a paper in which I evaluated a specific (recursive) Make build system and compared it to a SCons port. The performance results are not representative because the build system was very non-standard, but in this particular case the SCons port was actually faster.
Bottom line: If you really want to use Make to control your software builds, go for non-recursive Make because it makes your life far easier in the long run. Personally, I would rather use SCons for usability reasons (or Rake - basically any build system using a modern scripting language and which has implicit dependency support).
I made a half-hearted attempt at my previous job at making the build system (based on GNU make) completely non-recursive, but I ran into a number of problems:
The artifacts (i.e. libraries and executables built) had their sources spread out over a number of directories, relying on vpath to find them
Several source files with the same name existed in different directories
Several source files were shared between artifacts, often compiled with different compiler flags
Different artifacts often had different compiler flags, optimization settings, etc.
One feature of GNU make which simplifies non-recursive use is target-specific variable values:
foo: FOO=banana
bar: FOO=orange
This means that when building target "foo", $(FOO) will expand to "banana", but when building target "bar", $(FOO) will expand to "orange".
One limitation of this is that it is not possible to have target-specific VPATH definitions, i.e. there is no way to uniquely define VPATH individually for each target. This was necessary in our case in order to find the correct source files.
The main missing feature of GNU make needed in order to support non-recursiveness is that it lacks namespaces. Target-specific variables can in a limited manner be used to "simulate" namespaces, but what you really would need is to be able to include a Makefile in a sub-directory using a local scope.
EDIT: Another very useful (and often under-used) feature of GNU make in this context is the macro-expansion facilities (see the eval function, for example). This is very useful when you have several targets which have similar rules/goals, but differ in ways which cannot be expressed using regular GNU make syntax.
I agree with the statements in the refered article, but it took me a long time to find a good template which does all this and is still easy to use.
Currenty I'm working on a small research project, where I'm experimenting with continuous integration; automatically unit-test on pc, and then run a system test on a (embedded) target. This is non-trivial in make, and I've searched for a good solution. Finding that make is still a good choice for portable multiplatform builds I finally found a good starting point in http://code.google.com/p/nonrec-make
This was a true relief. Now my makefiles are
very simple to modify (even with limited make knowledge)
fast to compile
completely checking (.h) dependencies with no effort
I will certainly also use it for the next (big) project (assuming C/C++)
I have developed a non-recursive make system for a one medium sized C++ project, which is intended for use on unix-like systems (including macs). The code in this project is all in a directory tree rooted at a src/ directory. I wanted to write a non-recursive system in which it is possible to type "make all" from any subdirectory of the top level src/ directory in order to compile all of the source files in the directory tree rooted at the working directory, as in a recursive make system. Because my solution seems to be slightly different from others I have seen, I'd like to describe it here and see if I get any reactions.
The main elements of my solution were as follows:
1) Each directory in the src/ tree has a file named sources.mk. Each such file defines a makefile variable that lists all of the source files in the tree rooted at the directory. The name of this variable is of the form [directory]_SRCS, in which [directory] represents a canonicalized form of the path from the top level src/ directory to that directory, with backslashes replaced by underscores. For example, the file src/util/param/sources.mk defines a variable named util_param_SRCS that contains a list of all source files in src/util/param and its subdirectories, if any. Each sources.mk file also defines a variable named [directory]_OBJS that contains a list of the the corresponding object file *.o targets. In each directory that contains subdirectories, the sources.mk includes the sources.mk file from each of the subdirectories, and concatenates the [subdirectory]_SRCS variables to create its own [directory]_SRCS variable.
2) All paths are expressed in sources.mk files as absolute paths in which the src/ directory is represented by a variable $(SRC_DIR). For example, in the file src/util/param/sources.mk, the file src/util/param/Componenent.cpp would be listed as $(SRC_DIR)/util/param/Component.cpp. The value of $(SRC_DIR) is not set in any sources.mk file.
3) Each directory also contains a Makefile. Every Makefile includes a global configuration file that sets the value of the variable $(SRC_DIR) to the absolute path to the root src/ directory. I chose to use a symbolic form of absolute paths because this appeared to be the easiest way to create multiple makefiles in multiple directories that would interpret paths for dependencies and targets in the same way, while still allowing one to move the entire source tree if desired, by changing the value of $(SRC_DIR) in one file. This value is set automatically by a simple script that the user is instructed to run when the package is dowloaded or cloned from the git repository, or when the entire source tree is moved.
4) The makefile in each directory includes the sources.mk file for that directory. The "all" target for each such Makefile lists the [directory]_OBJS file for that directory as a dependency, thus requiring compilation of all of the source files in that directory and its subdirectories.
5) The rule for compiling *.cpp files create a dependency file for each source file, with a suffix *.d, as a side-effect of compilation, as described here: http://mad-scientist.net/make/autodep.html. I chose to use the gcc compiler for dependency generation, using the -M option. I use gcc for dependency generation even when using another compiler to compile the source files, because gcc is almost always available on unix-like systems, and because this helps standardize this part of the build system. A different compiler can be used to actually compile the source files.
6) The use of absolute paths for all files in the _OBJS and _SRCS variables required that I write a script to edit the dependency files generated by gcc, which creates files with relative paths. I wrote a python script for this purpose, but another person might have used sed. The paths for dependencies in the resulting dependency files are literal absolute paths. This is fine in this context because the dependency files (unlike the sources.mk files) are generated locally and rather than being distributed as part of the package.
7) The Makefile in each director includes the sources.mk file from the same directory, and contains a line "-include $([directory]_OBJS:.o=.d)" that attempts to include a dependency files for every source file in the directory and its subdirectories, as described in the URL given above.
The main difference between this an other schemes that I have seen that allow "make all" to be invoked from any directory is the use of absolute paths to allow the same paths to be interpreted consistently when Make is invoked from different directories. As long as these paths are expressed using a variable to represent the top level source directory, this does not prevent one from moving the source tree, and is simpler than some alternative methods of achieving the same goal.
Currently, my system for this project always does an "in-place" build: The object file produced by compiling each source file is placed in the same directory as the source file. It would be straightforward to enable out-of place builds by changing the script that edits the gcc dependency files so as to replace the absolute path to the src/ dirctory by a variable $(BUILD_DIR) that represents the build directory in the expression for the object file target in the rule for each object file.
Thus far, I've found this system easy to use and maintain. The required makefile fragments are short and comparatively easy for collaborators to understand.
The project for which I developed this system is written in completely self-contained ANSI C++ with no external dependencies. I think that this sort of homemade non-recursive makefile system is a reasonable option for self-contained, highly portable code. I would consider a more powerful build system such as CMake or gnu autotools, however, for any project that has nontrivial dependencies on external programs or libraries or on non-standard operating system features.
I know of at least one large scale project (ROOT), which advertises using [powerpoint link] the mechanism described in Recursive Make Considered Harmful. The framework exceeds a million lines of code and compiles quite smartly.
And, of course, all the largish projects I work with that do use recursive make are painfully slow to compile. ::sigh::
I written a not very good non-recursive make build system, and since then a very clean modular recursive make build system for a project called Pd-extended. Its basically kind of like a scripting language with a bunch of libraries included. Now I'm also working Android's non-recursive system, so that's the context of my thoughts on this topic.
I can't really say much about the differences in performance between the two, I haven't really paid attention since full builds are really only ever done on the build server. I am usually working either on the core language, or a particular library, so I am only interested in building that subset of the whole package. The recursive make technique has the huge advantage of making the build system be both standalone and integrated into a larger whole. This is important to us since we want to use one build system for all libraries, whether they are integrated in or written by an external author.
I'm now working on building custom version of Android internals, for example an version of Android's SQLite classes that are based on the SQLCipher encrypted sqlite. So I have to write non-recursive Android.mk files that are wrapping all sorts of weird build systems, like sqlite's. I can't figure out how to make the Android.mk execute an arbitrary script, while this would be easy in a traditional recursive make system, from my experience.