Gcc linker library files

The -l option is passed directly to the linker by GCC. Refer to your linker documentation for exact details. The general description below applies to the GNU linker. The linker searches a standard list of directories for the library. The directories searched include several standard system directories plus any that you specify with -L. Static libraries are archives of object files, and have file names like lib library.

Some targets also support shared libraries, which typically have names like lib library. If both static and shared libraries are found, the linker gives preference to linking with the shared library unless the -static option is used. It makes a difference where in the command you write this option; the linker searches and processes libraries and object files in the order they are specified.

If bar. Do not use the standard system startup files when linking. The standard system libraries are used normally, unless -nostdlib , -nolibc , or -nodefaultlibs is used.

Do not use the standard system libraries when linking. Only the libraries you specify are passed to the linker, and options specifying linkage of the system libraries, such as -static-libgcc or -shared-libgcc , are ignored.

The standard startup files are used normally, unless -nostartfiles is used. The compiler may generate calls to memcmp , memset , memcpy and memmove. These entries are usually resolved by entries in libc.

These entry points should be supplied through some other mechanism when this option is specified. Do not use the C library or system libraries tightly coupled with it when linking. This typically removes -lc from the link command line, as well as system libraries that normally go with it and become meaningless when absence of a C library is assumed, for example -lpthread or -lm in some configurations.

This is intended for bare-board targets when there is indeed no C library available. Do not use the standard system startup files or libraries when linking. No startup files and only the libraries you specify are passed to the linker, and options specifying linkage of the system libraries, such as -static-libgcc or -shared-libgcc , are ignored.

One of the standard libraries bypassed by -nostdlib and -nodefaultlibs is libgcc. In most cases, you need libgcc. In other words, when you specify -nostdlib or -nodefaultlibs you should usually specify -lgcc as well. This ensures that you have no unresolved references to internal GCC library subroutines.

Specify that the program entry point is entry. The argument is interpreted by the linker; the GNU linker accepts either a symbol name or an address. Produce a dynamically linked position independent executable on targets that support it. For predictable results, you must also specify the same set of options used for compilation -fpie , -fPIE , or model suboptions when you specify this linker option. Produce a static position independent executable on targets that support it.

A static position independent executable is similar to a static executable, but can be loaded at any address without a dynamic linker. On some targets this option also sets flags for the preprocessor, so it should be used consistently for both compilation and linking. Report of the libraries recognized by the dynamic linker without additional configuration, which includes directories:. When the -l foo option is encountered, gcc will first attempt to locate a shared object a.

Thus, the following situations can result from this search:. Because of these rules, the best way to select the static or dynamic version of a library for linking is having only that version found by gcc. This can be controlled to some extent by using or leaving out directories containing the library versions when specifying the -L path options. Additionally, because dynamic linking is the default, the only situation where linking must be explicitly specified is when a library with both versions present should be linked statically.

There are two possible solutions:. Usually, gcc is instructed to link against a library foo with the -l foo option. However, it is possible to specify the full path to the file lib foo.

From the file extension. However, specifying the full path to the library file is a less flexible method. The gcc option -Wl is a special option for passing options to the underlying linker. Syntax of this option differs from the other gcc options. The -Wl option is followed by a comma-separated list of linker options, while other gcc options require a space-separated list of options. The ld linker used by gcc offers the options -Bstatic and -Bdynamic to specify whether libraries following this option should be linked statically or dynamically, respectively.

After passing -Bstatic and a library to the linker, the default dynamic linking behaviour must be restored manually for the following libraries to be linked dynamically with the -Bdynamic option. To link a program, linking a library first statically libfirst. The -Wl option applies to the gold linker, too. Chapter Using Libraries with GCC. When creating the library, the full file name lib foo.

Section Resource use Static linking results in larger executable files which contain more code. Security Dynamically linked libraries which provide ABI compatibility can be updated without changing the executable files depending on these libraries. Compatibility Static linking appears to provide executable files independent of the versions of libraries provided by the operating system. A library which is not enabled for dynamic linking Fully static linking can be required for running code in an empty chroot environment or container.

However, static linking using the glibc-static package is not supported by Red Hat. The library code Header files. Static libraries are available as archive files. They contain a group of object files. The archive file has the file name extension. Dynamic libraries are available as shared objects. They are a form of executable file. A shared object has the file name extension.

The executable is " iwmingwgcc ". Thread model: posix gcc version 6. You probably should install these two packages too. However, to distribute the code produced, you need to distribute Cygwin Runtime Environment cygwin1. Reading man pages under CMD or Bash shell can be difficult. Hence, you need to include the current path. You also need to include the file extension, if any, i. In Unixes, the output file could be " a. Furthermore, you need to assign executable file-mode x to the executable file " a.

Compile and Link Separately The above command compile the source file into object file and link with other object files and system libraries into executable in one step. By default, the object file has the same name as the source file with extension of ". No linking with other object files or libraries. Linking is performed when the input file are object files ". GCC uses a separate linker program called ld. Compilation: The compiler compiles the pre-processed source code into assembly code for a specific processor.

The resultant assembly file is " hello. Assembly: The assembler as. Verbose Mode -v You can see the detailed compilation process by enabling -v verbose option. Shared Library A library is a collection of pre-compiled object files that can be linked into your programs via the linker. There are two types of external libraries: static library and shared library. A static library has file extension of ". When your program is linked against a static library, the machine code of external functions used in your program is copied into the executable.

A static library can be created via the archive program " ar. A shared library has file extension of ". When your program is linked against a shared library, only a small table is created in the executable. Before the executable starts running, the operating system loads the machine code needed for the external functions - a process known as dynamic linking.

Dynamic linking makes executable files smaller and saves disk space, because one copy of a library can be shared between multiple programs. Furthermore, most operating systems allows one copy of a shared library in memory to be used by all running programs, thus, saving memory. The shared library codes can be upgraded without the need to recompile your program.

You can list the contents of a library via " nm filename ". Searching for Header Files and Libraries -I , -L and -l When compiling the program, the compiler needs the header files to compile the source codes; the linker needs the libraries to resolve external references from other object files or libraries.

Utilities for Examining the Compiled Files For all the GNU utilities, you can use " command --help " to list the help menu; or " man command " to display the man pages. A rule consists of 3 parts: a target, a list of pre-requisites and a command, as follows: target : pre-req-1 pre-req Syntax of Rules A general syntax for the rules is: target1 [ target Phony Targets or Artificial Targets A target that does not represent a file is called a phony target.

Automatic Variables Automatic variables are set by make after a rule is matched. For example, we can rewrite the earlier makefile as: all: hello. For example, Search for. For example, Applicable for create. Comments start with a and go to the end of the line. Here is a simple Make Macro. A Macro Expansion may be treated as a textual replacement of the Make Macro. It has a Target named "clean" left of the colon ":" on the first line , no Dependencies right of the colon , and two Commands indented by tabs on the lines that follow.

The space before the colon is not required but added here for clarity. Also, these are both typically Artificial Targets, because they don't typically correspond to real files named "all" or "clean". The rule for "all" is used to incrementally build your system.