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6.3.3.3 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.