7.4.3 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.