Compiling mDNSResponder for Linux? - linux

I've been trying to compile the open source Bonjour framework developed by Apple for Linux. The problem I have is that when I run make with the option os=linux I get the following compile error:
struct sockaddr has no member named 'sa_len'
I've checked the struct sockddr and it indeed has no member named sa_len... So I'm confused as to why the framework is thinking that it should do!
Could anyone please give me some advice as to how I should be compiling mDNSResponder for Linux? Many thanks.

Looking in mDNSUNP.h one can see that if sa_len does not exist (such as on Linux), a macro NOT_HAVE_SA_LEN should be defined. If it's not defined in your case, try adding -DNOT_HAVE_SA_LEN to your compilation flags.

The Linux implementation of sockaddr doesn't have sa_len as a member, but the FreeBSD version does. Apple's implementation is based off of the FreeBSD version (parts of OS X pull from FreeBSD and NetBSD), hence why you're receiving that error. You can use an #ifdef to workaround it or add the compilation flag, as previously suggested.

Related

Vulkan.hpp compiling on one system but not another

I have the following generic function:
template <typename U>
auto CastVkArray(std::vector<U> &unique_handles)
{
std::vector<typename U::element_type> handles;
for(auto &u_handle : unique_handles) handles.push_back(*u_handle);
return handles;
}
The problem is/was that although I thought I instructed premake5 to use the version under a local directory in my project, it was using the system's installed version instead. The version mismatch meant that I was using an old vulkan.hpp header rather than the one I need.
Which I am temporarily using to convert unique handle arrays to non unique arrays. This code compiles just fine on my desktop (arch linux), however on my laptop (ubuntu) I get the error:
error: no type named ‘element_type’ in ‘class vk::UniqueHandle<vk::CommandBuffer>’
std::vector<typename U::element_type> handles;
I use premake 5 to generate my build environment and the script hasn't changed between the 2 systems. I checked that all the libraries I am using are the same version, in particualr, I made sure that the vulkan sdk is the same between the 2 computers.
I deleted and rebuilt my code multiple times to test for potential race conditions in compilation (just to see if anything changed), the error is always the same.
The one difference that I have found is that the reported version of premake in arch is 5.0.0-dev but on ubuntu it is 5.0.0-alpha14
But I have not been able to find the dev version on the official github repository of premake.

arm-linux-gnueabi-ld and fpc ppcrossarm still links to linux-i386

I was able to build a freepascal crosscompiler for arm, but now when i want to build a a simple graphical app in lazarus or rebuild LCL the compilation works until is called arm-linux-gnueabi-ld which one still looking for all graphics librarys in /usr/lib/gcc/i586-linux-gnu/4.9/ instead /usr/lib/gcc/arm-linux-gnueabi/4.9. so how i can fix it?
/usr/bin/arm-linux-gnueabi-ld: skipping incompatible /usr/lib/gcc/i586-linux-gnu/4.9/crtbegin.o when searching for /usr/lib/gcc/i586-linux-gnu/4.9/crtbegin.o
Put the relevant -FD or -Fl lines in your fpc.cfg under #ifdef i386
So e.g.
#ifdef cpui386
-Fl/lib
-Fl/usr/lib
-Fl/usr/lib/i586-linux-gnu/4.9
#endif
and add an appropriate entry for ARM
See here for a list of architecture specific defines. The Buildfaq has some more detailed information.

How to check the compiler version in Qt .pro file?

I want to build a Qt project using either GCC or an ARM compiler. In either environment I have to link different libraries.
How I can check if the current compiler is Linux's g++ and CROSS_COMPILE is 'arm-cortexa9neont-linux-gnueabi-'?
You can use the Platform Scope built in to QMake to set up the build differently depending on platform.
It's based on the mkspec's shipped with Qt and can be found in
[Where Qt's installed]/mkspecs
So in your case I guess it'll look something like this:
linux-arm-gnueabi {
//ARM stuff here
}
Please note that I have not tested this. I've only read what's in the documentation I have linked to.
If you want to know only type of processor, you can use Q_PROCESSOR_ARM macro.

how to handle "undefined symbol" errors for mismatched shared objects

I developed an application using a recent Glade, so I need it to load the UI from XML at runtime, using the GtkBuilder. If I try to run this on a distro which has too old a Gtk (e.g. RHEL 5), it will fail like this
undefined symbol: gtk_builder_new
which is normal and expected. But I wonder if there is a way to catch that error and instead display a GUI error dialog saying something like "your version of Gtk is not new enough"? This is an error that happens before my main() starts, so really the question is, is there a way to handle runtime linking errors? While googling, I found a mention of the concept of a linker plugin but I didn't find details about that yet. It sounds like something which would have to exist outside my application anyway, so maybe that's going a bit far.
I could use dlopen() to load Gtk, but that's ridiculous because I'd have to give the full path to it, and then I'd have to call dlsym() a lot to link every function that I need. ld-linux.so does the search for me. Is there a way I can use ld-linux.so to tell me the path to libgtk without actually loading it, then I check whether the version is new enough (or just whether gtk_builder_new exists), then finish the runtime linking if it's OK?
Well, it doesn't work that way on a Linux distro. What you're basically doing is bypassing the package manager.
The good way is to build your software on the target distro. At configuration time (call to ./configure) you will see that the requirements to use your software are not met. Or if you have no configure script, the compiler will yell at link time.
Then, it's the packager's job to fill in the requirement of the package. If in the .spec file of your RPM package you require gtk >= 2.16, then at installation time, the user will be shown the dialog telling him that some dependencies are missing, and he will see that his GTK version is too old.
You seem to be talking about the situation where you have compiled against headers with a recent enough version, but are running on a system where your library is not recent enough.
GTK provides a facility for checking that you have linked against a new enough version of the library. For example, if you need at least GTK 2.12 (which is the version in which GtkBuilder was introduced) you can use this code which will even display a nice GUI error dialog:
if (gtk_major_version < 2 || gtk_minor_version < 12) {
GtkWidget *dialog = gtk_message_dialog_new(NULL, GTK_DIALOG_MODAL,
GTK_MESSAGE_ERROR, GTK_BUTTONS_CLOSE,
"Your version of GTK is too old to run this program.");
gtk_message_dialog_format_secondary_text(GTK_MESSAGE_DIALOG(dialog),
"You need at least version 2.12.0; your version is %d.%d.%d.",
gtk_major_version, gtk_minor_version, gtk_micro_version);
gtk_dialog_run(GTK_DIALOG(dialog));
gtk_widget_destroy(dialog);
exit(-1);
}
Here is a workaround which might help: Rename your exe and create a bash script which calls it.
Now you can do this:
EXE=...name-of-your-real-executable...
LOG=logfile
$EXE > "$LOG" 2>&1 || {
if grep "undefined symbol: gtk_builder_new" "$LOG" ; then
... show error message ...
fi
}
[EDIT] Alternatively, you can create a really small test program which just contains a call to gtk_builder_new and run that during installation or in the test script.
That way, you don't need to check for a specific error message (which might get translated on non-English systems). If this small test program fails, you can be sure it's because of this missing symbol and nothing else.

fatal error C1084: Cannot read type library file: 'Smegui.tlb': Error loading type library/DLL

I am trying to build an old version of an application which consists of VC++ projects that were written in Visual Studio 2003.
My OS is Windows 7 Enterprise (64-bit).
When I try and build the solution I get the following errors:
error C4772: #import referenced a type from a missing type library; '__missing_type__' used as a placeholder
fatal error C1084: Cannot read type library file: 'Smegui.tlb': Error loading type library/DLL.
They both complain about the following import statement:
#import "Smegui.tlb" no_implementation
This is not a case of the file path being incorrect as renaming the Smegui.tlb file causes the compiler to throw another error saying it cannot find the library.
Smegui is from another application that this one depends on. I thought perhaps I was missing a dll but there is no such thing as Smegui.dll.
All I know about .tlb files is that they are a type library and you can create them from an assembly using tlbexp.exe or regasm.exe (the later also registers the assembly with COM)
There is also an Apache Ant build script which uses a custom task to invoke devenv.com to build the projects. This is the same script that the build server originally used to build the application. It gives me the same errors when I try and run it.
The strangest thing about this is that I knew it ought to work seeing as it is all freshly checked out from subversion. I tried many different combinations of admin vs user elevation, VS vs Ant build, cleaning, release.
I have got it to build successfully about 5 times but the build seems to be non-deterministic.
If anyone can shed some light on how this tlb stuff even works or what this error might mean I would greatly appreciate it.
I found a far more reliable solution: open the tlb with oleview.exe and then close it.
Not sure what this actually does but it works every time.
I think oleview is actually one of the samples included with Visual Studio but I haven't had the time to debug it and see what it is doing.
I ran into this error because one type library was trying to load a dependent type library, which it could not find. Even though the dependent type library was in the same directory, and even though that directory was in the searchable path, the compiler would error loading the first type library, but not mention the dependent type library in the error.
To find the pseudo-missing type library, I ran Process Monitor (procman64.exe) during the compile. This showed that after the reported type library had successfully loaded, a dependent type library could not be found. It even showed all of the places that it was looking for the dependent type library, none of which were where it should have been looking (e.g.: ).
The fix was to add a <PreBuildEvent> to the project to copy the dependent .tlb file to one of the directories that was actually being searched.
<PreBuildEvent>
<Command>copy /Y ..\Lib\Interop\CWSpeechRecLib.tlb .\</Command>
</PreBuildEvent>
http://msdn.microsoft.com/en-us/library/sce74ah7%28VS.71%29.aspx
smegui.tlb is referencing some other tlb that the compiler can't find. If you have the .idl for smegui you might be able to figure out what the other is. I suspect the missing tlb is something that original build machine had registered but that your machine doesn't have registered.
A type library is a binary description of a set of interfaces, coclasses and enums. They're usually generated for COM components, in the case of tlbexp and regasm the tlb is created from the assembly metadata. For native COM components they are usually generated from an idl (Interface Description Language) file by the midl tool.
Edit:
I just noticed you're on x64 Windows. Are you building the project with a new version of Visual Studio? If so, are you targeting x86 or x64? If the latter, it may simply be a 32bit component that the compiler can't find (or less likely, a x64 component the x86 compiler can't find if you are targeting x86), for WOW64 the registry is virtualized for x86 vs. x64 applications.
Well I finally found out why I managed to get it to build sometimes and not others... sort of.
So long as I ran the build script with elevated administrator permissions and let that get as far as it could until that error occurred, then run the build script again as a protected administrator succeeded. Those steps must be done in that exact order with no other steps in between. If I try build in Visual Studio it does not work (although I did get it to succeed once). Probably some kind of virtualisation issue although it still doesn't quite make sense.
Well I don't need help on this any more and I know it's probably impossible to fully answer this question without knowing exactly what the build is doing. However if anyone does have any more thoughts I would happily receive them.
Cheers,
Steiny

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