Two copies of constant appearing in the compiled Elf

问题

We are basically using sparc architecture and our language is Ada we are using gnat compiler to compile our code. We observed something funny.

Some of the constant in our code are having two or more copies.

file.adb:

With FileConsts; USE FileConsts
Procedure SomeProcedure is
A : LONG_FLOAT;
Begin
    A := cSomeConstant;
End SomeProcedure;

FileConsts.ads

cSomeConstant : CONSTANT LONG_FLOAT := 100.0;

In the Map file we have basically

.rodata 0x40010000 (0x8)file.o
.rodata 0x40010008 pfileconsts__csomeconstant

In the Assembly it is accessing the area of file.o, i.e 0x40010000 instead if 0x40010008. In the binary file the value at 0x40010000 and 0x40010008 is actually same, so program is behaving as expected. But why would the compiler do that

If any other package(file2.adb) also accesses the cSomeConstant, it is making another copy in the section

.rodata 0x40010010 (0x8)file2.o

Again the value in binary file is same as cSomeConstant

Why compiler is behaving this way? How to suppress this behavior ?

It really is confusing while debugging.

回答1:

You should remember that typed "constants" aren't static in Ada.

If you want a static constant, use a "named number":

Some_Constant : constant := 100.0;

(I don't know which code the compiler will generate in this case.)

来源：https://stackoverflow.com/questions/50407178/two-copies-of-constant-appearing-in-the-compiled-elf