Macros: Definition, Substitution, and Suffix Replacement

New Append Operator

+=

This is the new append operator that appends a SPACE followed by a word or words, onto the existing value of the macro.

Conditional Macro Definitions

:=

This is the conditional macro definitions operator that indicates a conditional (targetwise) macro definition. A makefile entry of the form:

target := macro = value

indicates that macro takes the indicated value while processing target and its dependencies.