The glibc manual explains that a bindtextdomain() call is needed as part of i18n setup because a package's message files may be installed in a directory other than glibc's. If I assume this never happens with my package, that is my package is always installed on a system where glibc is the system libc or else with the same --prefix as glibc (or libintl), can I skip the call?
In other words, is there a default for the message file search path?
My reason is that it is a global initialization routine, and as such fits uneasily into a general purpose shared library.
Related
I am modifying the malloc.c and hooks.c file in glibc library and my modification uses shm_open().
Now to build glibc, the Man page of shm_open() says that I need to link with -lrt.
The problem that I am facing is, as far as I know, librt is produced during the build process of glibc. How can I modify the makefile(s) to build glibc and also link librt?
Or is there any other way to achieve this?
Please check if you have to recompile glibc at all. Usually, this is not necessary for replacing malloc. You can interposed glibc's malloc implementation from a DSO if you implement a certain set of functions:
Replacing malloc
This mechanism relies on ELF symbol interposition (perhaps via LD_PRELOAD).
Userspace package built for and along with root file system image of some embedded Linux-based system here (using Yocto project) apparently uses autotools - one can see Makefile.am's and configure.ac in package's sources. pkg-config or its successor seems to be used too (.pc.in is present), however out-of scope here.
Package in focus here does it this way (by involving autotools) as in the beginning of its development it was apparently the line of lowest resistance to copy and adopt build scripts from similar but already-existing package.
Actually autotools seem to be dispensable when building with Yocto, as Yocto build system meta data do specify target precisely enough for every target. For good reason standard build flow in Yocto is download, unpack, patch, configure, build,... with scan-and-detect-target-environment not included in this chain.
Now I wonder if it was good to streamline package's build process by removing autotools stage. I'm going to conduct it by proceeding in sequence of few steps starting with replacing .am file with real makefile. Question is if it will be sufficient enough to find env. variables defined and used in .am and .ac then transfer them to makefile? Remaining target-device specification should actually come from Yocto build system meta data. Possibly it will work this straightforward if to build package in scope of root file system image build. But how to ensure build environment provides complete target device specification when building only this package bitbake package-name?
Replacing autotools with a bare makefile isn't a trivial operation, as https://nibblestew.blogspot.co.uk/2017/12/a-simple-makefile-is-unicorn.html demonstrates nicely.
If you don't want to use autotools in your packages then alternatives such as Meson are generally faster.
Could anyone offer some suggestions (or resources) on how I could package a GO program that uses git2go, libssl and libssh2 such that it doesn't require the end user to install these libraries separately?
I am only targeting Linux distros (if it matters)
One way would be to build those dependencies statically as well and use PKG_CONFIG_PATH point to your own copies so everything gets linked statically. That should make CMake choose the static versions.
But if the goal is to avoid depending on the user-installed libraries rather than making everything a single executable, I would recommend shipping the libraries and working with the load path to make sure they get loaded. With gcc you'd pass -Wl,-R to set the search path in the binary itself, so you can set where to search for the shared libraries you're shipping with your app. With go it looks like you can pass -r to the linker (via -ldflags or manually) to do the same thing.
libgit2 is rather extensible, so there is a third option which is to implement the TLS stream and SSH transport in Go and plug those into a version of libgit2 without support for these. This is however a significant amount of work.
I've used zlib for ages and never thought about the fact that it is named slightly unconventionally. While most libraries on Linux follow the naming convention of lib<name>.so for shared objects and lib<name>.a for archives, zlib is named zlib.so/zlib.a. My question is: how does gcc/ld know to look for zlib.so when I use -lz as a link flag?
I understand that for linking, gcc invokes ld, which searches for libraries in certain default paths and any path specified with -L, and it appends the lib and .so or .a. parts as necessary. Oddly, gcc's manual page for linking options only mentions that the linker can find archives; there is no mention of the .so extension. The man page for ld at least mentions both extensions, but still only mentions searching by prepending lib to the specified library name. How does ld know to add the lib after the z for zlib? I've never seen this happen to another library.
gcc has several different methods for linking libraries, shared or static. If you specify -lz, gcc is going to look for libz.so (possibly with some version bits between the libz and the .so, but the important part is the file name will start with libz and end with .so), or for libz.a (again, possibly with version info) if you are compiling statically, or as a fallback if the shared library does not exist. If you specify -lzlib it will look for libzlib.so (which is not the standard name - the package is often named zlib, but the library itself is libz). Another way of linking would be to not use the -l<lib> option, and just specify /path/to/zlib.so or -L /path/to zlib.so (or zlib.a if you want). In this case, the library doesn't have to have the lib prefix, but you would have to explicitly provide any version info, unless provisions are made for a symbolic link or something similar to provide the literal name zlib.so.
Applications can also load shared libraries at runtime via dlopen() and it's other associated functions, in which case the library can also be named whatever you want it to be (this doesn't work for static libraries, of course).
So, if the library you are looking at is actually called zlib.so, then it is not being found by gcc ... -lz, unless it just happens to be a symbolic link to libz.so (or vice versa, in which case gcc is really just using libz.so, which happens to have the same content as your zlib.so). However gcc might be using it if the build process explicitly names the library in the link stage (not using -l<lib>) or if your application loads it via dlopen() (but in that case, it's not really linked to your program - it's just loaded at run time).
My question may be silly, but I need to use a library from its source code without compiling it to a library form first. The tool in question is FreeType. Is this possible?
You can add all the files from the FreeType source distribution into your own project, and try to get them to compile alongside. However, the FreeType compilation procedure is a bit tricky, if I recall correctly.
It is probably easier to compile FreeType as a static library, then link your own program with the generated library. If you do that, your executable will have no dependency on the FreeType runtime library.
It's called bundling: instead of shipping your code with JAR files of some library, or even just requiring the library in your INSTALL document, you simply copy the source code into your project and have it built by your build system instead of using it pre-built. It may require adapting your build system a bit, and you need to make sure you have the right to redistribute the library in source form, but it can sometimes make sense.
MPlayer did this with ffmpeg for a long time, and XEN with the Linux kernel (notionally, they ship patches instead of the entire kernel tree). The disadvantage is, of course, that you effectively fork the library, and don't get any updates of the code whatsoever unless you re-rip their code and get it to build in your project again.
You can get the sourcecode of FreeType from http://freetype.sourceforge.net if that's what you mean.