I'm learning ESP-IDF platform and now want to create a library in order to be able to structure my code properly in the future.
I've done some research and found few things, for instance a library that could be as an example. The only issue with it being too large, I can't clearly see what's the bare minimum for the simplest library code.
What is the minimum configuration for an ESP-IDF static library that can be built into a .a file?
A minimal ESP-IDF component would have an empty component.mk file, C/C++/ASM source file(s), and header file(s) in include subdirectory. At build time, all source files of the component will be compiled and then linked into a static library, which can be found in build/component_name/libcomponent_name.a. This is further explained in ESP-IDF build system documentation.
There are a few such simple components in the ESP-IDF itself, e.g. log.
Related
I'm porting an old C++ project to run on RHEL 6.7 with gcc 4.4.7. The code was originally made to run on an SGI machine.
I have a library .a which is presumed to have been compiled on the old machine (and thus there's no hope of running it in the new one) however, along with this .a file I also have the headers and source files. I am assuming that these are the ones that are used to make the .a file. The Makefile that was used is now long gone, I just have the source code.
My question is, is there a way to "reverse engineer" the library? I would like to know what functions the .a library contains so I can make it on my machine.
I will add that I am new to static and shared libraries so I'm not entirely sure what the .a file contains or how it is any different from including the headers.
Update:
I have looked into the included code and realized that the C files only work to interface with functions defined using Fortran95. I think that now I'm supposed to build the Fortran95 codebase and somehow interface that with the C code. Once I do that I will have a library that should (hopefully) compile in my native system. How can I do this?
How to build a .bundle from source code?
This might sound like a simple problem but it has been hurdling me for a week...
Here is my problem:
I have a bunch of .c and .h files that are organized in a folder and its sub folders. The source code was written and compiled with gcc make and tested by many other make tools. The source code has some utilities and command line tools and it has more code that serve as library for those utilities and tools. It is the files that serve as libraries that I want to reuse. (By library I don't mean static library or something, I just mean that some .c and .h files in certain subfolders provide functions that can be called by some other .c files. I want to be able to call those functions, too)
Yet my problem is more complex than that: I need to build those .c and .h into a bundle to reuse it. I am not writing my application in C; I am developing in Unity and Unity can only take in .bundle files on Mac OS.
Here is my goal:
Organize the source code folder in a proper way so that I can build them into a bundle in Xcode 4.
Here is where I got stuck:
When building the project I got the following error:
Duplicate symbol _main in
/Users/zeningqu/Library/Developer/Xcode/DerivedData/ccn-cfygrtkrshubpofnfxalwimtyniq/Build/Intermediates/ccn.build/Debug/ccn.build/Objects-normal/i386/ccndsmoketest.o
and
/Users/zeningqu/Library/Developer/Xcode/DerivedData/ccn-cfygrtkrshubpofnfxalwimtyniq/Build/Intermediates/ccn.build/Debug/ccn.build/Objects-normal/i386/ccnd_main.o
for architecture i386
I can relate to this error because I can find lots of main entries in the source code. Most of them are test utilities.
Here is what I tried:
I tried removing all those utility .c files but with no luck. The error is still there. I delete and delete until some files cannot find the definition of the function they are calling. So I had to stop there.
Though I wasn't able to build a bundle I was able to build a C/C++ static library (with an .a extension). After I got the .a file I tried to put it into another Xcode project and tried to build it into a bundle. I could build a bundle in that way, but then I had problem accessing the content of the bundle. How do I call functions defined in a .a static library if that library is hidden in a bundle? I read about Apple's documentation which says:
Note: Some Xcode targets (such as shell tools and static libraries) do
not result in the creation of a bundle or package. This is normal and
there is no need to create bundles specifically for these target
types. The resulting binaries generated for those targets are intended
to be used as is.
(quoted from: https://developer.apple.com/library/mac/#documentation/CoreFoundation/Conceptual/CFBundles/AboutBundles/AboutBundles.html#//apple_ref/doc/uid/10000123i-CH100-SW1)
Here is what I thought about:
I thought about replacing all main with something like main_sth. But the source code was not written by me so I didn't want to modify it. (It just doesn't feel like a proper way of doing things to me...)
I learnt that Xcode has gcc compiler built in. So I guess if gcc can make it, so can Xcode? It's just a wild guess - I am not familiar with Xcode and gcc.
Here is a summary of my questions:
Is there a way to properly organize a pile of code previously compiled and made by gcc make so that they can be built into an Xcode bundle?
Is it meaningful to put a .a library in an Xcode project and build it into a bundle? If it is meaningful, how do I call functions defined in .a after it is built into a bundle?
Is it proper to just replace all main() entries with something else?
Alright I think I have figured out at least one solution to the problem.
The duplicate main error was caused by a bunch of main entries in my source code. When the code was compiled by gcc make, I guess the author defined a sort of compilation order so that duplicate mains won't be an issue. (If you know how to do this, please let me know. I barely know make tools.) But when I just add the entire source code folder into my Xcode project, of course Xcode would complain during linking...
As I was unwilling to modify the source code (because the source code library is not developed by me), I decided to use another strategy to walk around this problem.
If your duplicate main error was reported from your own code, you can stop reading here. But if you are like me, with a bunch of gcc compiled source code and badly need a bundle yet don't know what to do, I may be able to help.
Okay here is what I did:
I set up an empty workspace.
I built a C/C++ static library project.
Import my entire source code folder into the static library project.
Set some header search path for the static library project.
Build the static library project. (Now I have a .a library which I could link against)
I set up another project, with a bundle target.
At the bundle project -> Build Phases -> Link Binary with Libraries, add the .a library that I just built.
At the bundle project -> edit scheme -> Build, add the static library project to the scheme and move it up the list so that it is built prior to my bundle project.
Then add .h files of my library project to my bundle project as references.
After that, add a .c file in my bundle project that basically functions as a wrapper. I picked a function that I want to call in Unity, wrote a wrapper function in the new .c file, and was able to build the bundle.
After several trial and error, I was able to import the bundle into Unity and was able to call the test function from Unity.
I was really excited about this! Though it's not completed yet I think this gives me hope and I am confident I can use the source code now! And the best thing about this solution is that I don't have to modify the library code developed by others. Whenever they update their code, I just update my .a library and that's it!
Though I have listed 11 steps I still feel that there are lots of details that I missed. So here are my references:
I followed this tutorial to build my source code into a static library: http://www.ccnx.org/?post_type=incsub_wiki&p=1315
I followed this blog to link static library against my bundle code and twist build phases and search headers: http://blog.carbonfive.com/2011/04/04/using-open-source-static-libraries-in-xcode-4/
I followed this doc to import my bundle to Unity3D Pro as a plugin: http://unity3d.com/support/documentation/Manual/Plugins.html
I strongly recommend the second reference because that's what solved my problem!
Though the problem is almost solved there are still a few things that I haven't figured out:
I don't know if a wrapper function is at all necessary. I will try this out tomorrow and come back to update.
-- I am coming back to update: the wrapper function is NOT necessary. Just make sure you have all the headers in your bundle project and you will be able to use all the data structures and call functions defined in your headers.
I haven't used NSBundle class though I read a few docs about it. Previously I was thinking about using that class to access my .a library encapsulated in my bundle, but as I found the solution I wrote above, I didn't try the class out.
Lastly, if you have better solution, please don't hesitate to let me know!
I tried to follow the steps in the accepted answer, but had no luck. In the end, I realised step 10 needed to be modified slightly:
Create a dummy.c under (.bundle) project and the dummy.c can just be totally empty.
Remove the setting for the library you want to link inside Link Binary With Libraries
Instead use -Wl,-force_load,$(CONFIGURATION_BUILD_DIR)/libYourLib.a or -all_load to Other Linker Flags
PS: And also can use sub-project instead of workspace. and use Target Dependencies instead of Edit Scheme to achieve the same effect.
I have C project of a library (using CDT). Configurations for both static and dynamic linking for several platforms. Several examples of the library usage is also included in the project. What is the best way to build these examples with the library? If I would like to build both the library and examples (linking the library just built) in one configuration?
I suppose I have to use custom makefile. Do I have to create makefile for the whole project (several of them, one for each platform), or is there any way how to include examples makefile to the automatic one?
Each example has only one source file, so the only things I need to do in my makefile are to determine which compiler is used, add some flags and link with the library which was built (I would include the make examples command as the post-build step).
As I didn't find any solution for this, I use custom makefile for the whole build. I also found a nice advice somewhere: if you want advanced build functions, use advanced build system.
There are appear to be methods of creating a fat static library ala "http://stackoverflow.com/questions/3520977/build-fat-static-library-device-simulator-using-xcode-and-sdk-4". Is this recommended? Any special steps (i.e., disabling thumb)
Also, if I do use the fat static library, will monotouch/xcode clear out any unused code in the final product?
You definitely need to turn Thumb code off so you can link properly against the library. As far as creating the fat static library goes, I can only say that anecdotally I've done this for a few third-party libraries that I've used and haven't run into issues.
I assume you already know that you need to create the bindings necessary to make calls to the objective-c library from your MonoTouch code and add extra gcc flags in the project properties to link in the static lib. If not, you can get that information on how to do that from the MonoTouch website.
we're building a cross-platform utility which must have a small footprint. We've been pulling header files from boost as and when we need them but now we must link against some boost C++ thread code. The easiest immediate solution was to create our own custom library using CMake's "add_library" command to create a static library composed of some boost thread source files. These compile without any problems.
The difficulty arises when I try to link to this library from an executable. Visual Studio 2008 returns an error saying that it cannot link to "libboost_thread-vc90-mt-sgd-1_40.lib". What really puzzles me is that I've grepped through all the source code and CMake config files and I can't find any reference to this libboost library, leading me to think that this has been autogenerated in some way.
This works OK in Linux, can anyone point out why I'm experiencing these issues in Windows?
#Gearoid
You found the correct reason for your problem, but not the correct solution. The BOOST_AUTO_LINK_NOMANGLE is an internal, i.e. for library authors, definition to control the auto-linking. The user level definition is BOOST_ALL_NO_LIB which when defined disables the auto-linking feature for all Boost Libraries code you use. This is described in the user.hpp configuration header (see user.hpp near the bottom and the Boost Config documentation). You can also control this on a per library level as describe in that header.
Ok, well, it turns out that Boost uses this auto-link feature for Visual Studio which embeds references to a mangled (ie, platform-compiler-mult-threaded, etc) boost library name.
The header file which controls this is called "auto_link.hpp" which lives in the config directory of the boost include tree. There's a special preprocessor definition called "BOOST_AUTO_LINK_NOMANGLE" which toggles this behaviour.
Another triumph of mediocrity for Microsoft.