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The manpage to errno tells the following story: The <errno.h> header file defines the integer variable errno, which is set by system calls and some library functions in the event of an error to indicate what went wrong. Its value is significant only when the return value of the call indicated an error (i.e., -1 from most system calls; -1 or NULL from most library functions); a function that succeeds is allowed to change errno. Valid error numbers are all nonzero; errno is never set to zero by any system call or library function.
This directory contains ports of popular 3rd-party software to Genode. Usage ----- At the root of the 'libports' repository, there is 'Makefile' automating the task of downloading and preparing the library source codes. By just typing 'make', you get an overview of the available libraries and further instructions. In the common case, you might just want to prepare all packages by issuing: ! make prepare Alternatively, you can select individual packages to prepare by specifying their base names (without the version number) as command-line argument. For example, the following command prepares both the C library and the Freetype library: ! make prepare PKG="libc freetype" After having prepared the 'libports' repository, you are ready to include the repository into the build process by appending it to the 'REPOSITORIES' declaration of your '<build-dir>/etc/build.conf' file. Under the hood -------------- For each library, there is a file contained in the 'libports/ports/' subdirectory. The file is named after the library and contains the library-specific rules for downloading the source code and installing header files. How does 'libports' relate to the other repositories? ----------------------------------------------------- Most libraries hosted in the 'libports' repository expect a complete C library, which is provided with the 'libc' package. Please do not forget to prepare the libc package when using any of the other libports packages. The libc, in turn, depends on the 'os' repository for its back end. Because the 'os' repository is the home of the dynamic linker, libraries contained in 'libports' are safe to assume the presence of the dynamic linker and, thus, should be built as shared libraries.