Any extra linker-specific option you may require could easily be specified with the -Wl, prefix on the gcc command line if not already available as a plain gcc option. It is mostly a matter of taste: you would use ld directly when the command-lines are simpler than using gcc. That would be when you are just using the linker to manipulate a small number of shared objects, e. Because you can pass options to ld via the -Wl option, often people will recommend just using gcc to manage the command-line.
Stack Overflow for Teams — Collaborate and share knowledge with a private group. Create a free Team What is Teams? Collectives on Stack Overflow. Learn more. When i should use ld instead of gcc? Ask Question. Asked 5 years, 9 months ago. Active 3 years, 6 months ago. Viewed 10k times. 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.
The location counter may never be moved backwards. Then file2 appears, also with a byte gap following before file3 is loaded. The linker uses "lazy evaluation" for expressions; it only calculates an expression when absolutely necessary.
The linker needs the value of the start address, and the lengths of memory regions, in order to do any linking at all; these values are computed as soon as possible when the linker reads in the command file. However, other values such as symbol values are not known or needed until after storage allocation.
Such values are evaluated later, when other information such as the sizes of output sections is available for use in the symbol assignment expression. You may create global symbols, and assign values addresses to global symbols, using any of the C assignment operators:. Two things distinguish assignment from other operators in ld expressions. You must place a trailing semicolon " ; " at the end of an assignment statement.
The first two cases are equivalent in effect--both define a symbol with an absolute address. The last case defines a symbol whose address is relative to a particular section see section Specifying Output Sections.
When a linker expression is evaluated and assigned to a variable, it is given either an absolute or a relocatable type. An absolute expression type is one in which the symbol contains the value that it will have in the output file; a relocatable expression type is one in which the value is expressed as a fixed offset from the base of a section. The type of the expression is controlled by its position in the script file. A symbol assigned within a section definition is created relative to the base of the section; a symbol assigned in any other place is created as an absolute symbol.
Since a symbol created within a section definition is relative to the base of the section, it will remain relocatable if relocatable output is requested. For example, to create an absolute symbol whose address is the last byte of an output section named. For instance, the sizes of sections cannot be known until after allocation, so assignments dependent upon these are not performed until after allocation. If the result of an expression is required, but the value is not available, then an error results.
In some cases, it is desirable for a linker script to define a symbol only if it is referenced, and only if it is not defined by any object included in the link. The command language includes a number of built-in functions for use in link script expressions. Primarily useful to assign an absolute value to a symbol within a section definition, where symbol values are normally section-relative. ADDR section Return the absolute address of the named section. Johan Johan Add a comment. Active Oldest Votes.
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