I recently came across ShiftPWM, which is optimized to control RGB LEDs using shift registers.
I downloaded the source code and was able to run the example provided on my breadboard no problem. I even tweaked the sketch a bit and feel comfortable using the functions in the ShiftPWM library.
I would like to include the ShiftPWM functionality in a current project I'm working on, which already has a ton of library files. I'd like to #include "ShiftPWM.h into my Registers.h file, so that I can use my own syntax and object-oriented hierarchy to light up my LEDs.
In the example arduino sketch, I need to define a few constants before including the ShiftPWM library file:
#define SHIFTPWM_NOSPI
const int ShiftPWM_latchPin = 2;
const int ShiftPWM_dataPin = 4;
const int ShiftPWM_clockPin = 3;
const bool ShiftPWM_invertOutputs = true;
const bool ShiftPWM_balanceLoad = false;
#include "ShiftPWM.h"
So I figured I could simply copy these lines into my Registers.h file, as well as the setup code and other functions that go about lighting up the LEDs.
But, when I do this and try to compile my arduino sketch, which only includes Registers.h, my compiler gives me the following (abbreviated) errors:
multiple definitions of '__vector_11'
.../ShiftPWM/ShiftPWM.h:175 first defined here
multiple definitions of 'ShiftPWM'
.../ShiftPWM/ShiftPWM.h:175 first defined here
The line it is referring to is this:
ISR(TIMER1_COMPA_vect) {
ShiftPWM_handleInterrupt();
}
My research indicates this line of code has something to do with the timers used by the arduino to run interrupts. People often get the 'multiple definitions of __vector_11' error when they try to run the arduino Servo and Tone library, for instance, because they both attempt to use timer1.
I am wondering why I am getting this error simply by attempting to link to the ShiftPWM library from my own custom library. Nowhere in my code do I manually set any sort of timer. I am assuming it stems from some linking issue, but I really can't figure out what that may be.
Any help is appreciated.
Related
I have to create a SQLite database using System.Data.SQLite and using C++/CLI but I run into problems. Unfortunately, using C# is not an option, if it was then there is no problem. (Please don't advise me not to use C++/CLI, it is not an option in this project.)
In C# the following code works without any problem.
using System.Data.SQLite;
void CreateDb(String file)
{
SQLiteConnection.CreateFile(file);
}
The equivalent code in C++/CLI is not without its problems.
using namespace System::Data::SQLite;
void CreateDb(System::String ^file)
{
SQLiteConnection::CreateFile(file); // error C2039
}
The exact error txt for C2039 is:
// error C2039: 'CreateFileA' : is not a member of 'System::Data::SQLite::SQLiteConnection'
If I take a closer look at the definition of CreateFile I get the following choice
#define CreateFile CreateFileW - c:\Program Files (x86)\Microsoft SDKs\Windows\v7.0A\Include\WinBase.h(9292)
#define CreateFile CreateFileA - c:\Program Files (x86)\Microsoft SDKs\Windows\v7.0A\Include\WinBase.h(9294)
Which leads to the following lines in WinBase.h
#ifdef UNICODE
#define CreateFile CreateFileW
#else
#define CreateFile CreateFileA
#endif // !UNICODE
The Microsoft SDK is muddling with exact the name that I need and SQLite does not provide me with CreateFile[AW] versions.
So I tried this before the code calling SQLiteConnection.CreateFile(file) and I do this isolated so that other code is affected by it.
#ifdef CreateFile
#undef CreateFile
#endif
It solves my problem (for now) but how safe is this?
Is there a better way of solving this problem?
Your advise is much appreciated.
The #undef is how I've always handled this.
how safe is this?
This is safe.
You may have this problem again if you have other name collisions. The compile errors resulting from such a name collision are easy to diagnose, now that you know what you're looking for, so it will be easy to add additional #undef directives if needed.
If you need to call the Win32 CreateFile, you will need to type CreateFileA or CreateFileW explicitly, but that's not a big hassle.
Is there a better way of solving this problem?
Yes, but it's not always possible.
The better way is to not #include <Windows.h> in the files where you use SQLite. This avoids the problem entirely. However, it's not always possible to organize your program like this, so #undef is usually the solution.
(This next paragraph doesn't apply to your scenario with SQLite: You're using the managed version, so there's no headers. This next bit applies to C++ libraries that include library headers. I'm including it for completeness in case someone is writing plain C++.)
One other thing to watch out for here is #include-ing the Windows headers before library headers. In that case, the class definition itself will have CreateFile renamed to CreateFileA. If you use #undef with that, you'll get the opposite error from what you showed. You can leave the #define in place, which will sometimes end up working, but this is rather fragile, so I would avoid this scenario.
(I ran into this once with MFC headers in a C++ application: The changed method name ended up everywhere, even Intellisense showed the name as ending in "A". It worked anyway because the vTable was initialized inside the MFC DLL, and so all that mattered in the calling application was that the vTable pointed at the right method, which it was.)
I need to change to reference of a function in a mach-o binary to a custom function defined in my own dylib. The process I am now following is,
Replacing references to older functions to the new one. e.g _fopen to _mopen using sed.
I open the mach-o binary in MachOView to find the address of the entities I want to change. I then manually change the information in the binary using a hex editor.
Is there a way I can automate this process i.e write a program to read the symbols, and dynamic loading info and then change them in the executable. I was looking at the mach-o header files at /usr/include/mach-o but am not entire sure how to use them to get this information. Do there exist any libraries present - C or python which help do the same?
interesting question, I am trying to do something similar to static lib; see if this helps
varrunr - you can easily achieve most if not all of the functionality using DYLD's interposition. You create your own library, and declare your interposing functions, like so
// This is the expected interpose structure
typedef struct interpose_s {
void *new_func;
void *orig_func;
} interpose_t;
static const interpose_t interposing_functions[] \
__attribute__ ((section("__DATA, __interpose"))) = {
{ (void *)my_open, (void *) open }
};
.. and you just implement your open. In the interposing functions all references to the original will work - which makes this ideal for wrappers. And, you can insert your dylib forcefully using DYLD_INSERT_LIBRARIES (same principle as LD_PRELOAD on Linux).
At work, I recently took training on MATLAB/Simulink, including the Simulink Coder that can generate C code for embedded applications. I wanted to try my hand at it, so I bought an Arduino, and dove in. I am able to write simple sketches with no problem, but have been hitting a brick wall when trying to integrate the code generated by Simulink.
I initially used the Arduino IDE, then Eclipse with the Arduino plug-in, and finally Xcode with the embedXcode templates. (My work machine with Simulink is a PC, but I'm not allowed to install "unauthorized software", so I did the rest on my home Mac.) All three use the same avr-gcc compiler.
All three had the same point of failure: "Undefined Reference" errors on the generated function calls. I believe this to be a linker issue rather than basic syntax or header inclusion, as the Eclipse and Xcode code-completion are working OK, and if I change the call signature in any way, the error changes. I can make references to the data structures OK.
As far as I can tell, the default makefiles are set up to compile and link any files within the folder. A "mass_model2.o" file is being created, at least with Xcode. Finally, if I manually write a separate "myFunction.c" and "MyFunction.h" file with a simple function call, this does compile and run on the device as expected.
In desparation, I copied the entire contents of the generated ".c" file, and pasted them in the main sketch file after my setup() and loop() functions, keeping the same ".h" references, and removed the ".c" file from the project. This actually did compile and run! However, I should not have to touch the generated code in order to use it.
What do I need to do to get this to compile and link properly?
The Simulink code is quite verbose, so here are the key parts:
mass_model2.h excerpts:
#include "rtwtypes.h"
#include "mass_model2_types.h"
/* External inputs (root inport signals with auto storage) */
typedef struct {
int16_T PotPos; /* '<Root>/PotPos' */
} ExternalInputs_mass_model2;
/* External outputs (root outports fed by signals with auto storage) */
typedef struct {
int16_T ServoCmd; /* '<Root>/ServoCmd' */
} ExternalOutputs_mass_model2;
/* External inputs (root inport signals with auto storage) */
extern ExternalInputs_mass_model2 mass_model2_U;
/* External outputs (root outports fed by signals with auto storage) */
extern ExternalOutputs_mass_model2 mass_model2_Y;
/* Model entry point functions */
extern void mass_model2_initialize(void);
extern void mass_model2_step(void);
mass_model2.c excerpts:
#include "mass_model2.h"
#include "mass_model2_private.h"
/* External inputs (root inport signals with auto storage) */
ExternalInputs_mass_model2 mass_model2_U;
/* External outputs (root outports fed by signals with auto storage) */
ExternalOutputs_mass_model2 mass_model2_Y;
/* Model step function */
void mass_model2_step(void)
{
// lots of generated code here
}
/* Model initialize function */
void mass_model2_initialize(void)
{
// generated code here
}
The other referenced headers, "rtwtypes.h" and "mass_model2_private.h" define specific types that are used by the generated code, like int16_T. These files are included in the project, and I do not receive any errors associated with them.
In my sketch file, the setup() function calls mass_model2_initialize(). loop() reads my input (a potentiometer), sets the value in mass_model2_U.PotPos, and calls mass_model2_step(). It then gets mass_model2_Y.ServoCmd and writes the value to a servo for output, and finally has a delay().
You can use this download, http://www.mathworks.com/matlabcentral/fileexchange/24675, with Simulink, Simulink Coder and Embedded Coder. Make sure you have the correct version numbers of each tool.
The #include "Arduino.h" statement is required on the main sketch.
is the OpenGL function glDrawBuffers(GLsizei n, const GLenum *bufs) available in Qt?
I'm trying to pass multiple render targets to my fragment shader, QtCreator says the function is not declared in this scope. The idea is to have a frame buffer object with two colorbuffers, and draw with the fragment shader to those two buffers.
FIXED:
Just had to add #define GL_GLEXT_PROTOTYPES 1 to the offending file :(
Qt offers only rudimentary access to OpenGL functions. Loading shaders and textures are amongst them. Render targets are not. Just use a proper extension loader library like GLEW. GLEW will nicely coexist with Qt's functionality.
Derive from QGLWidget and override glInit to call glewInit after calling initializeGL
We just spent some time fixing this. We are running Qt 5.2.1 on OSX 10.8 and Ubuntu 14.04 (sorry no WINDOWS experience) and created an OpenGL3.2 context using QGLFormat.
In OSX there is no problem as all OpenGL3.2 functions (to set uniforms, draw buffers, etc..) are defined in:
#include "OpenGL/gl3.h" ///< already included by Qt.. so nothing to do
On Linux on the other hand, we have to include BOTH of these:
#include "GL/gl.h"
#include "GL/glext.h" ///< not included by Qt!!! manually include it
We also attempted to have our QGLWidget class inherit from QGLFunctions_3_2_Core (this class defines its own copy of glDrawBuffer etc...), but this wasn't useful and simply resulted in a segfault:
Program received signal SIGSEGV, Segmentation fault. 0x0000000000407068
in glGetUniformLocation (this=0xbc5820, name=0x407cd0 "view_projection", program=1)
at /usr/include/qt5/QtGui/qopenglfunctions_3_2_core.h:1075 1075
return d_2_0_Core->GetUniformLocation(program, name);
We also investigated the "#define GL_GLEXT_PROTOTYPES 1" above, but this was only useful when we were using glcorearb.h (you can download this header online).
The only real use of the --whole-archive linker option that I have seen is in creating shared libraries from static ones. Recently I came across Makefile(s) which always use this option when linking with in house static libraries. This of course causes the executables to unnecessarily pull in unreferenced object code. My reaction to this was that this is plain wrong, am I missing something here ?
The second question I have has to do with something I read regarding the whole-archive option but couldn't quite parse. Something to the effect that --whole-archive option should be used while linking with a static library if the executable also links with a shared library which in turn has (in part) the same object code as the static library. That is the shared library and the static library have overlap in terms of object code. Using this option would force all symbols(regardless of use) to be resolved in the executable. This is supposed to avoid object code duplication. This is confusing, if a symbol is refereed in the program it must be resolved uniquely at link time, what is this business about duplication ? (Forgive me if this paragraph is not quite the epitome of clarity)
Thanks
There are legitimate uses of --whole-archive when linking executable with static libraries. One example is building C++ code, where global instances "register" themselves in their constructors (warning: untested code):
handlers.h
typedef void (*handler)(const char *data);
void register_handler(const char *protocol, handler h);
handler get_handler(const char *protocol);
handlers.cc (part of libhandlers.a)
typedef map<const char*, handler> HandlerMap;
HandlerMap m;
void register_handler(const char *protocol, handler h) {
m[protocol] = h;
}
handler get_handler(const char *protocol) {
HandlerMap::iterator it = m.find(protocol);
if (it == m.end()) return nullptr;
return it->second;
}
http.cc (part of libhttp.a)
#include <handlers.h>
class HttpHandler {
HttpHandler() { register_handler("http", &handle_http); }
static void handle_http(const char *) { /* whatever */ }
};
HttpHandler h; // registers itself with main!
main.cc
#include <handlers.h>
int main(int argc, char *argv[])
{
for (int i = 1; i < argc-1; i+= 2) {
handler h = get_handler(argv[i]);
if (h != nullptr) h(argv[i+1]);
}
}
Note that there are no symbols in http.cc that main.cc needs. If you link this as
g++ main.cc -lhttp -lhandlers
you will not get an http handler linked into the main executable, and will not be able to call handle_http(). Contrast this with what happens when you link as:
g++ main.cc -Wl,--whole-archive -lhttp -Wl,--no-whole-archive -lhandlers
The same "self registration" style is also possible in plain-C, e.g. with the __attribute__((constructor)) GNU extension.
Another legitimate use for --whole-archive is for toolkit developers to distribute libraries containing multiple features in a single static library. In this case, the provider has no idea what parts of the library will be used by the consumer and therefore must include everything.
An additional good scenario in which --whole-archive is well-used is when dealing with static libraries and incremental linking.
Let us suppose that:
libA implements the a() and b() functions.
Some portion of the program has to be linked against libA only, e.g. due to some function wrapping using --wrap (a classical example is malloc)
libC implements the c() functions and uses a()
the final program uses a() and c()
Incremental linking steps could be:
ld -r -o step1.o module1.o --wrap malloc --whole-archive -lA
ld -r -o step2.o step1.o module2.o --whole-archive -lC
cc step3.o module3.o -o program
Failing to insert --whole-archive would strip function c() which is anyhow used by program, preventing the correct compilation process.
Of course, this is a particular corner case in which incremental linking must be done to avoid wrapping all calls to malloc in all modules, but is a case which is successfully supported by --whole-archive.
I agree that using —whole-archive to build executables is probably not what you want (due to linking in unneeded code and creating bloated software). If they had a good reason to do so they should have documented it in the build system, as now you are left to guessing.
As to your second part of the question. If an executable links both a static library and a dynamic library that has (in part) the same object code as the static library then the —whole-archive will ensure that at link time the code from the static library is preferred. This is usually what you want when you do static linking.
Old query, but on your first question ("Why"), I've seen --whole-archive used for in-house libraries as well, primarily to sidestep circular references between those libraries. It tends to hide poor architecture of the libraries, so I'd not recommend it. However it's a fast way of getting a quick trial working.
For your second query, if the same symbol was present in a shared object and a static library, the linker will satisfy the reference with whichever library it meets first.
If the shared library and static library have an exact sharing of code, this may all just work. But where the shared library and the static library have different implementations of the same symbols, your program will still compile but will behave differently based on the order of libraries.
Forcing all symbols to be loaded from the static library is one way of removing confusion as to what is loaded from where. But in general this sounds like solving the wrong problem; you mostly won't want the same symbols in different libraries.