I was assuming that they are the same flags for different compilers, but, it seems to me there are differences more than that. Just I wanted to make sure.
-Wall turns on a lot of useful warnings and depending on your style and sense of perfection you'll find the compiler nagging at you. Solving these will improve code quality and solve bugs before they have the opportunity to be found.
-Weverything warns about pretty much every single little thing you could find. Even some things that are perfectly fine according to the C++ language. This is more useful in an IDE setting than it helps you when compiling code.
Related
I find it terribly hard to find any "formal" documentation about fortran online. I want to know how to optimize the code (compilation wise) I tried the -O3 using f95 compiler but I want to know if there is anything else I can do. As for icc, this is a future issue and I only want to be "prepared".
I can't understand why it is terribly hard for you to find 'formal' documentation about Fortran online. I just Googled the search term optimizing fortran programs and got about 4.5M hits. On the first page about 6 (out of 10) would be worth looking at at least briefly; some of the links pointed back here to SO questions and answers.
To help you prepare for using Intel compilers here's a link to their documentation . If you wander around the Intel site you'll find useful information on optimising your programs which is applicable to many compilers, not just the Intel products.
Your first resource for optimisation-by-compiler ought to be the documentation for your compiler, which will show you all the options available. It ought to tell you, for example, what options -O3 engages. On most compilers I've used the -O optimisation option is a short hand for a number of other flags, and it's interesting to see the effect of those flags individually or in combinations other than all-or-none.
The Fortran Company web-site is another useful jumping-off point for your searches. I could go on, but won't.
The thinking is that since variadic templates are a compile time feature, there will be little ABI impact or runtime behaviour change. Is this possible?
I specifically want the benefit of faster compile times for boost::mpl::vector and boost::mpl::string.
Rephrasing the question...
Is it possible to mix c++03 and c++11 code by separating them into libraries? I.e. we use quite a few 3rd party c++ libraries which are compatible with gcc 4.3 but we are moving on too gcc 4.7 and intend to use c++11 features where possible/makes sense. Or is it impossible to mix c++11 and c++03?
You should compile and link everything using the same tools running in compatible modes. You can't cherry-pick features like this.
The ABI impact comes in, for example, increased virtual function tables for standard I/O classes. It is not safe to mix things around.
I cant give a qualified answer, but from what I understood is, that lots of people would be concerned if this kind of backward-compatibility would be broken. As far as I understood there is nothing in the new C++11 that makes it necessary to rebuild everything. Thus, it could only be your specific compiler that would make that necessary. For the GCC I dont't expect it, although, the different libstdc++ versions could create "issues".
My strong guess is, that on a typical (intel-) linuxes you should be able to create two independent libs with different decently new versions of the gcc (maybe >4.x) and use/link them into a final program. You may have some things in there twice, though. I had some minor solvable issues with threads in 4.7.0 and <thread>. I don't know if they would create a good or bad mix with other thread-libs (eg. boost). However, you don't want to use gcc-4.7.0 for your production code, yet. And before a final gcc compiler is out, only a statement from the responsible projects team can give you certainty.
I've just finished a library in Objective-C that I compiled as a Static Library for distribution.
I'd wanted to know what chances to get this decompiled are out there.
Do you know any software that can do this?
If so, how could I protect me better?
EDIT: My static lib is made for iPhone / ARM
I created an algorithm that depending on the some parameters of the app, it can run as demo or as full code. You init the object with X variables and unlock the full version. I was wondering if they'll be able to see this algorithm so they can create a key generator.
If it executes, it can be decompiled. Objective-C is particularly easy to decompile into readable code thanks to its dynamic features. If you want to make things a little bit harder, you could write most of your code in plain C and strip the executable — which of course has the tradeoff of making your application design harder to manage. But be honest with yourself: If somebody wants to crack your code, you are not going to be able to stop them. Crackers have practically unlimited amounts of time and enthusiasm and will actually be excited by any novel efforts you put in to stop them. Nobody has yet made uncrackable software, and the biggest corporations in the world have tried. You're not going to do better than them, especially if you need to ask about it on Stack Overflow.
Take the time that you would have put into thwarting decompilation and use it to make your product better — that will have a much better ROI.
It's not clear what you are trying to protect yourself from. Yes, it can be reverse engineered. The simplest tool is otool, part of the standard developer distribution:
otool -tV <library>
From that they run up to things like IDA Pro, which has iPhone support and is very nice for this kind of work. In between, I'm really surprised that I haven't seen a rework of otx for iPhone/ARM yet. I wouldn't be surprised to see one show up eventually. And of course there's gdb if you're trying to work out how things flow and what the data is at various points.
If you have more details about what you're trying to protect yourself from, there may be some targeted answers. Beyond that, read Chuck's comments.
ChanceGetsDecompiled = ExpectedGainFromBeingDecompiled / PopularityOfLibrary
Well if you REALLY want to know I would try decompiling it your self. You don't say if this is for PPC, Intel, or ARM which makes a difference. Here is a decompiler for Intel
i386 Decompiler
I don't know what you could do (I don't think there is much) to limit this. Code can always be reverse engineered. Be happy that your not using java or .net. Their decompilation is so nice.
I work on a runtime system for an application domain that is very performance sensitive. We go to a lot of effort to maintain backward compatibility with older compiler versions, including avoiding more recently-implemented language constructs, and synthesizing them for the older versions.
However, I'm concerned that this effort does a disservice to our users, by enabling them to continue to use compiler releases that are costing them huge amounts of performance. Unfortunately, I haven't been able to find any real comparison of execution performance across releases. If anyone has links to reports on this issue, please post them.
I'd really like to see benchmarks that cover a wide span of releases (if you can get back to 3.2, that's amazing) and applications/tests
A bit old, but still shows how much GCC have progressed: This benchmark shows that GCC 4.4 with it's new register allocator (IRA) and the focus on optimization made it become almost as powerful as ICC (Which is considered to be he most aggressive optimizer available).
I highly recommend using GCC 4.4[.1].
If you are on Windows, and using MinGW 3.4.x, you should upgrade NOW, since that specific port is rather buggy and generates horrible code.
I think Xcode is a good IDE, but having used Eclipse for Java development in the past I am quite underwhelmed by XCode's code completion and error/warning feedback. (Most of the time, XCode seems to simply try to match the beginning of a text fragment to "words" in the same document, without even using type information to try to determine the appropriateness of a suggested completion.)
Does anyone have ideas or tricks to make XCode approach Eclipse's cleverness, or to realistically develop Cocoa apps with other IDE:s than XCode?
EDIT: Worth keeping an eye on this: code.google.com/p/objectiveclipse/
The good news is, Apple’s working on the problem. One of the goals of the clang compiler project is to create a reusable parser which can be used for better code completion and refactoring support. Indications are that this has borne fruit in the latest Snow Leopard seeds.
Quite simply: no.
You can do almost everything by hand using your favorite text editor but it's not at all recommended. Try designing interfaces without Interface Builder for example.
My advice would be to just stick with Xcode and learn its way of doing things. Yes, it will be different and sometimes might not be "better" in your Eclipsed eyes. Console yourself in the fact that Apple's managed to release some great products using Xcode.
My personal experience is that, each time I use Xcode, I find a new trick which I can add to my bag. Xcode is far more full-featured than what you might think at first (or second) glance.
I've long voiced my rants about what's wrong with Xcode (and what's not wrong with Xcode). But you really don't want to use another tool. And without breaking NDA: Xcode 3.2 with SnowLeopard: Hooray. (Compared to what we have; not compared to what we might want.)
That said, to your original question about code completion, I personally turn off auto-completion in favor of on-demand completion. I find it far more useful and less distracting. In the Code Sense panel, set "Automatically Suggest" to "Never" and make sure the other two options are selected ("Show arguments in pop-up list" and "Insert argument placeholders...") This will do completion in a pop-up box when you hit Escape, making it easy to scroll through looking for what you want. I find that I have to type a lot less this way, especially for methods that are not unique for many characters. 80% of the time, it's highlighting the right thing already.
I have certainly felt your pain — as an experienced Java developer and frequent Eclipse user, I've wished for the same features myself. Unfortunately, I'm not aware of anything that fits the bill. I don't think there was any satisfactory resolution to this SO question, either.
However, I think you'll be quite happy with the improvements to Xcode code completion coming in Snow Leopard — it's vastly smarter about filtering the list of possible completions. Also, there are new conveniences for coding, such as inserting a starting bracket when you forgot one, etc. To my knowledge, there is still no predictive compiling like Eclipse, though.
Is anyone aware of an IDE other than Eclipse that supports predictive compiling and warning/error reporting? Does Eclipse itself support the feature for languages other than Java, such as C++? I'm led to wonder whether the fact that Java is built with independent .java files rather than .h and .c/.cpp/.m files makes it simpler to predictively compile. Also, anything compiled with gcc requires a little more care and attention than the comparatively simpler javac command. Any thoughts?
Check out JetBrains' new IDE called "App Code". It's still in the Early Access Program, but even with the Early Access bugs it is hands-down better than xcode 4.
http://www.jetbrains.com/objc/
emacs and/or vim
Xcode does have some context awareness, when you are sending a message to an object it will generally have the "ESC" list pull up meaningful arguments.
One thing I strongly recommend is looking into text macros. These are not really type aware, but they can save a ton of typing - for instance, after #implementation type "init" and then hit control-. (period) to activate the text macro. It will fill out a whole init method for you. You can create your own, or override the existing macros.