GNATPrep #

GNATPrep is a C-style preprocessor for the GNAT toolchain.

#if <expression> [then]
   -- ...
#elsif <expression> [then]
   -- ...
#end if;

Valid <expression> Values

<symbol>
<symbol>'Defined

<symbol> =  "<value>"
<symbol> =  <symbol>
<symbol> =  <integer>
<symbol> >  <integer>
<symbol> >= <integer>
<symbol> <  <integer>
<symbol> <= <integer>

not <expression>
<expression> and <expression>
<expression> or  <expression>
<expression> and then <expression>
<expression> or else  <expression>
( <expression> )

Integers must be non-negative in the range 0 .. 2**31 - 1.
<symbol>’Defined is only True when it has been defined either in a definitions file or a -D switch.
Combining, for example, or and not operators requires parentheses.

Example

#if Win32'Defined then
   -- Windows-specific code
#elsif POSIX'Defined then
   -- POSIX-specific code
#else
   -- ...
#end if;

Switch	Description
`"-gnatep"`	Specifies the definitions file to use. `<Project_Name>'Project_Dir` can be used to search from the project file’s directory. `"-gnatep=prep.def"`
`"-gnateD"`	Defines a symbol for use.
`"-gnateG"`	Generate the preprocessed source.
`"-x"`	Builder switch to when using `"gnatep="` to ensure the preprocessor data file is found.

Definitions#

GNATPrep can either have symbols defined with the -D switch or use a definitions file that is a simple sequence of:

symbol := value

And may be accessed outside of preprocessor lines by using $symbol anywhere except for comments and string literals. They should be ASCII values and their values may be:

Empty (for null substitution)
A string literal (using Ada’s syntax)
Any sequence of characters from the set {letters, digits, period, underline}

Comments in the same style as Ada may also be in the file.

Data Files#

Data files contain “preprocessor control lines” to control the function for individual files. The general for is "file.adb" ["definitions_file.prep"] {switches} and files may be either the file name sans its directory path or wildcard * in order to match all files that do not have a data file associated with them. There may not be two lines that start with either the same file or with an *.

"file_1.adb" "defs_1.prep" -u

* -c -DVersion=V2

Switch	Description
`-b`	Causes both preprocessor lines and the lines deleted by preprocessing to be replaced by blank lines, preserving the line number. This switch is always implied; however, if specified after `-c` it cancels the effect of `-c`.
`-c`	Causes both preprocessor lines and the lines deleted by preprocessing to be retained as comments marked with the special string `–!`.
`-C`	Causes comments to be scanned and preprocessor symbols to be substituted.
`-D`	Define or redefine symbol to have new_value as its value. You can write symbol as either an Ada identifier or any Ada reserved word aside from `if`, `else`, `elsif`, `end`, `and` or `and then`. You can write new_value as a literal string, an Ada identifier or any Ada reserved word. A symbol declared with this switch replaces a symbol with the same name defined in a definition file. `-Dsymbol[=new_value]`
`-r`	Causes `Source_Reference` pragma to be generated.
`-s`	Causes a sorted list of symbol names and values to be listed on the standard output file.
`-u`	Causes undefined symbols to be treated as having the value `False` in the context of a preprocessor test. If you don’t specify this switch, an undefined symbol in a `#if` or `#elsif` test is treated as an error.

GNATPrep#

Definitions#

Data Files#

GNATPrep #