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(ld.info)Input Section Common

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Input section for common symbols
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   A special notation is needed for common symbols, because in many
object file formats common symbols do not have a particular input
section.  The linker treats common symbols as though they are in an
input section named `COMMON'.

   You may use file names with the `COMMON' section just as with any
other input sections.  You can use this to place common symbols from a
particular input file in one section while common symbols from other
input files are placed in another section.

   In most cases, common symbols in input files will be placed in the
`.bss' section in the output file.  For example:
     .bss { *(.bss) *(COMMON) }

   Some object file formats have more than one type of common symbol.
For example, the MIPS ELF object file format distinguishes standard
common symbols and small common symbols.  In this case, the linker will
use a different special section name for other types of common symbols.
In the case of MIPS ELF, the linker uses `COMMON' for standard common
symbols and `.scommon' for small common symbols.  This permits you to
map the different types of common symbols into memory at different
locations.

   You will sometimes see `[COMMON]' in old linker scripts.  This
notation is now considered obsolete.  It is equivalent to `*(COMMON)'.