7.1.2 Environment Variables

The variables in this section are optional, but if defined, they will be used by the compiler. The compiler driver, or other subprogram, may choose to determine an appropriate value for some of the following environment variables if they are unset. The driver, or other subprogram, takes advantage of internal knowledge about the installation of the compiler. As long as the installation structure remains intact, with all subdirectories and executables remaining in the same relative position, the driver or subprogram will be able to determine a usable value.

Table 7-1. Compiler-Related Environmental Variables
Variable	Definition
`XC16_C_INCLUDE_PATH` `PIC30_C_INCLUDE_PATH`	This variable’s value is a semicolon-separated list of directories, much like `PATH`. When the compiler searches for header files, it tries the directories listed in the variable, after the directories specified with `-I` but before the standard header file directories. If the environment variable is undefined, the preprocessor chooses an appropriate value based on the standard installation. By default, the following directories are searched for the following include files: `<install-path>\include` and `<install-path>\support\h`
`XC16_COMPILER_ PATH` `PIC30_COMPILER_ PATH`	The value of the variable is a semicolon-separated list of directories, much like `PATH`. The compiler tries the directories thus specified when searching for subprograms, if it can’t find the subprograms using `PIC30_EXEC_PREFIX`.
`XC16_EXEC_ PREFIX` `PIC30_EXEC_ PREFIX`	If the environment variable is set, it specifies a prefix to use in the names of subprograms executed by the compiler. No directory delimiter is added when this prefix is combined with the name of a subprogram, but you can specify a prefix that ends with a slash if you wish. If the compiler cannot find the subprogram using the specified prefix, it tries looking in your `PATH` environment variable. If the environment variable is not set or set to an empty value, the compiler driver chooses an appropriate value based on the standard installation. If the installation has not been modified, this will result in the driver being able to locate the required subprograms. Other prefixes specified with the `-B` command line option take precedence over the user- or driver-defined value of the variable. Under normal circumstances it is best to leave this value undefined and let the driver locate subprograms itself.
`XC16_LIBRARY_ PATH` `PIC30_LIBRARY_ PATH`	This variable’s value is a semicolon-separated list of directories, much like `PATH`. This variable specifies a list of directories to be passed to the linker. The driver’s default evaluation of this variable is: `<install-path>\lib; <install-path>\support\gld`.
`XC16_OMF` `PIC30_OMF`	Specifies the OMF (Object Module Format) to be used by the compiler. By default, the tools create ELF object files. If the environment variable has the value `coff`, the tools will create COFF object files.
`TMPDIR`	If the variable is set, it specifies the directory to use for temporary files. The compiler uses temporary files to hold the output of one stage of compilation that is to be used as input to the next stage: for example, the output of the preprocessor, which is the input to the compiler proper.