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For each of the packages Builder, Compiler, Binder, and
Linker, you can specify a ^Default_Switches^Default_Switches^
attribute, a Switches attribute, or both;
as their names imply, these ^switch^switch^-related
attributes affect the ^switches^switches^ that are used for each of these GNAT
components when
gnatmake is invoked. As will be explained below, these
component-specific ^switches^switches^ precede
the ^switches^switches^ provided on the gnatmake command line.
The ^Default_Switches^Default_Switches^ attribute is an attribute
indexed by language name (case insensitive) whose value is a string list.
For example:
package Compiler is
for ^Default_Switches^Default_Switches^ ("Ada")
use ("^-gnaty^-gnaty^",
"^-v^-v^");
end Compiler;
The Switches attribute is indexed on a file name (which may or may
not be case sensitive, depending
on the operating system) whose value is a string list. For example:
package Builder is
for Switches ("main1.adb")
use ("^-O2^-O2^");
for Switches ("main2.adb")
use ("^-g^-g^");
end Builder;
For the Builder package, the file names must designate source files
for main subprograms. For the Binder and Linker packages, the
file names must designate ALI or source files for main subprograms.
In each case just the file name without an explicit extension is acceptable.
For each tool used in a program build (gnatmake, the compiler, the binder, and the linker), the corresponding package contributes a set of ^switches^switches^ for each file on which the tool is invoked, based on the ^switch^switch^-related attributes defined in the package. In particular, the ^switches^switches^ that each of these packages contributes for a given file f comprise:
Switches (f),
if it is specified in the package for the given file,
^Default_Switches^Default_Switches^ ("Ada"),
if it is specified in the package.
If neither of these attributes is defined in the package, then the package does not contribute any ^switches^switches^ for the given file.
When gnatmake is invoked on a file, the ^switches^switches^ comprise
two sets, in the following order: those contributed for the file
by the Builder package;
and the switches passed on the command line.
When gnatmake invokes a tool (compiler, binder, linker) on a file, the ^switches^switches^ passed to the tool comprise three sets, in the following order:
Builder package in the project file supplied on the command line;
The term applicable ^switches^switches^ reflects the fact that gnatmake ^switches^switches^ may or may not be passed to individual tools, depending on the individual ^switch^switch^.
gnatmake may invoke the compiler on source files from different
projects. The Project Manager will use the appropriate project file to
determine the Compiler package for each source file being compiled.
Likewise for the Binder and Linker packages.
As an example, consider the following package in a project file:
project Proj1 is
package Compiler is
for ^Default_Switches^Default_Switches^ ("Ada")
use ("^-g^-g^");
for Switches ("a.adb")
use ("^-O1^-O1^");
for Switches ("b.adb")
use ("^-O2^-O2^",
"^-gnaty^-gnaty^");
end Compiler;
end Proj1;
If gnatmake is invoked with this project file, and it needs to compile, say, the files a.adb, b.adb, and c.adb, then a.adb will be compiled with the ^switch^switch^ ^-O1^-O1^, b.adb with ^switches^switches^ ^-O2^-O2^ and ^-gnaty^-gnaty^, and c.adb with ^-g^-g^.
The following example illustrates the ordering of the ^switches^switches^ contributed by different packages:
project Proj2 is
package Builder is
for Switches ("main.adb")
use ("^-g^-g^",
"^-O1^-)1^",
"^-f^-f^");
end Builder;
package Compiler is
for Switches ("main.adb")
use ("^-O2^-O2^");
end Compiler;
end Proj2;
If you issue the command:
gnatmake ^-Pproj2^/PROJECT_FILE=PROJ2^ -O0 main
then the compiler will be invoked on main.adb with the following sequence of ^switches^switches^
^-g -O1 -O2 -O0^-g -O1 -O2 -O0^
with the last ^-O^-O^ ^switch^switch^ having precedence over the earlier ones; several other ^switches^switches^ (such as ^-c^-c^) are added implicitly.
The ^switches^switches^
^-g^-g^
and ^-O1^-O1^ are contributed by package
Builder, ^-O2^-O2^ is contributed
by the package Compiler
and ^-O0^-O0^ comes from the command line.
The ^-g^-g^ ^switch^switch^ will also be passed in the invocation of Gnatlink.
A final example illustrates switch contributions from packages in different project files:
project Proj3 is
for Source_Files use ("pack.ads", "pack.adb");
package Compiler is
for ^Default_Switches^Default_Switches^ ("Ada")
use ("^-gnata^-gnata^");
end Compiler;
end Proj3;
with "Proj3";
project Proj4 is
for Source_Files use ("foo_main.adb", "bar_main.adb");
package Builder is
for Switches ("foo_main.adb")
use ("^-s^-s^",
"^-g^-g^");
end Builder;
end Proj4;
-- Ada source file:
with Pack;
procedure Foo_Main is
...
end Foo_Main;
If the command is
gnatmake ^-PProj4^/PROJECT_FILE=PROJ4^ foo_main.adb -cargs -gnato
then the ^switches^switches^ passed to the compiler for foo_main.adb are
^-g^-g^ (contributed by the package Proj4.Builder) and
^-gnato^-gnato^ (passed on the command line).
When the imported package Pack is compiled, the ^switches^switches^ used
are ^-g^-g^ from Proj4.Builder,
^-gnata^-gnata^ (contributed from package Proj3.Compiler,
and ^-gnato^-gnato^ from the command line.
When using gnatmake with project files, some ^switches^switches^ or
arguments may be expressed as relative paths. As the working directory where
compilation occurs may change, these relative paths are converted to absolute
paths. For the ^switches^switches^ found in a project file, the relative paths
are relative to the project file directory, for the switches on the command
line, they are relative to the directory where gnatmake is invoked.
The ^switches^switches^ for which this occurs are:
^-I^-I^,
^-A^-A^,
^-L^-L^,
^-aO^-aO^,
^-aL^-aL^,
^-aI^-aI^, as well as all arguments that are not switches (arguments to
^switch^switch^
^-o^-o^, object files specified in package Linker or after
-largs on the command line). The exception to this rule is the ^switch^switch^
^–RTS=^–RTS=^ for which a relative path argument is never converted.