8.3.3.3 Example of unused subprogram/data elimination

Here is a simple example:

    with Aux;
    
    procedure Test is
    begin
       Aux.Used (10);
    end Test;
    
    package Aux is
       Used_Data   : Integer;
       Unused_Data : Integer;
    
       procedure Used   (Data : Integer);
       procedure Unused (Data : Integer);
    end Aux;
    
    package body Aux is
       procedure Used (Data : Integer) is
       begin
          Used_Data := Data;
       end Used;
    
       procedure Unused (Data : Integer) is
       begin
          Unused_Data := Data;
       end Unused;
    end Aux;

Unused and Unused_Data are never referenced in this code excerpt, and hence they may be safely removed from the final executable.

    $ gnatmake test
    
    $ nm test | grep used
    020015f0 T aux__unused
    02005d88 B aux__unused_data
    020015cc T aux__used
    02005d84 B aux__used_data
    
    $ gnatmake test -cargs -fdata-sections -ffunction-sections \\
         -largs -Wl,--gc-sections
    
    $ nm test | grep used
    02005350 T aux__used
    0201ffe0 B aux__used_data

It can be observed that the procedure Unused and the object Unused_Data are removed by the linker when using the appropriate options.