The SIZE_SYMBOL attribute defines a space separated list of section size symbol names to be created by the link-editor. A size symbol is a global-absolute symbol that represents the size, in bytes, of the segment. These symbols can be referenced in your object files. In order to access the symbol within your code, you should ensure that symbol_name is a legal identifier in that language. The symbol naming rules for the C programming language are recommended, as such symbols are likely to be accessible from any other language.
The “=” form of assignment can be used to establish an initial value, and can only be used once per link-editor session. The “+=” form of SIZE_SYMBOL concatenates the new list to the end of the existing list, and can be used as many times as desired.