Unable to link C source code with Ada static library (Error: libnewapi.a(unit1.o):unit1.adb:undefined reference to `__gnat_rcheck_CE_Overflow_Check')

Question

I want to integrate my Ada static library (libnewapi.a) with my C source code (main.c). I do not have any issues generating the static library but when trying to link it with main.c. I get the below link error, libnewapi.a(unit1.o):unit1.adb:(.text+0x31): undefined reference to `__gnat_rcheck_CE_Overflow_Check' I am not using this reference in my main.c not in any of my Ada files. I do not know why this reference was added automatically. It is crucial that I need to link my main.c using a static Ada library for my project. I do not know where I am going wrong. Help is much appreciated. Thanks!

I am generating libnewapi.a using a GPR as below,

    -- ada_gen_a.gpr
    project ada_gen_a is
       for Languages use ("Ada");
       for Source_Dirs use ("./");
       for Library_Name use "newapi";
       for Library_Dir use "./Lib/";
       for Library_Kind use "static";

       package Naming is
          for Spec_Suffix ("ada") use ".ads";
          for Body_Suffix ("ada") use ".adb";
          for Separate_Suffix use ".adb";
          for Dot_Replacement use ".";
          for Casing use "mixedcase";
       end Naming;

       Ada_Switches := ("-gnato", "-O2");

       package Compiler is
          for Default_Switches ("ada") use Ada_Switches;
       end Compiler;

       package Binder is
          for Default_Switches ("Ada") use ("-n","-Lada");
       end Binder;
    end ada_gen_a;

Ada Sourcefiles:

    --  unit1.ads
    package Unit1 is
       function Add (A, B : Integer) return Integer;
       pragma Export (C, Add, "ada_add");
    end Unit1;

    -- unit1.adb
    package body Unit1 is
       function Add (A, B : Integer) return Integer is
       begin
          return A + B;
       end Add;
    end Unit1;

C Source File:

    /* main.c */
    #include <stdio.h>
    extern void ada_add (void);
    int main (int argc, char *argv[])
    {
       int a = 21, b = 7, c = 0;
       printf ("%d", a);
       printf ("%d", b);
       c = ada_add(a,b);
       printf ("%d", c);
       return 0;
    }

I am using the below GPR to link the above main.c with the Ada static library generated using ada_gen_a.gpr.

    -- Ada_Use_A.gpr
    with "newapi.gpr";
    project Ada_Use_A is

       for Languages use ("C");
       for Source_Dirs use (".");
       for Source_Files use ("main.c");

       package Naming is
          for Casing use "mixedcase";
       end Naming;

       Ada_Switches := ("-gnato", "-O2");

       package Compiler is
          for Default_Switches ("C") use ("-O2", "-Wall");
          for Default_Switches ("Ada") use Ada_Switches;
       end Compiler;

       package Binder is
          for Default_Switches ("Ada") use ("-n","-Lada");
       end Binder;

       for Main use ("main.c");

    end Ada_Use_A;

    -- newapi.gpr
    project newapi is
       for Externally_Built use "true";
       for Source_Files use ();
       for Library_Dir use ".\lib\";
       for Library_Name use "newapi";
       for Library_Kind use "static";
    end newapi;

When I try to build the Ada_Use_A.gpr GPS I get the below linker error, libnewapi.a(unit1.o):unit1.adb:(.text+0x31): undefined reference to __gnat_rcheck_CE_Overflow_Check' gprbuild: link of main.c failed`

I don't know about ADA specifically, but it is common for programming language implementations to rely on a library of runtime support functions. For a compiled language, the compiler might insert calls to such functions to implement various language features, even though the source code does not explicitly express such calls. Given that `gnat` is GNU's ADA compiler, I am inclined to think that something along those lines explains where the calls to `__gnat_rcheck_CE_Overflow_Check` came from. Presumably you need at least to link an additional library to resolve those. — John Bollinger, Jul 21 '23 at 14:55
You could try `-gnato0`, which "causes the behavior of the compiler to match the default for older versions where overflow checking was suppressed by default." — trashgod, Jul 21 '23 at 16:23
I wonder whether [this answer](https://stackoverflow.com/a/76720427/40851) (and the question it’s an answer to) might be relevant? — Simon Wright, Jul 23 '23 at 20:27

score 1 · Answer 1 · answered Jul 25 '23 at 17:21

In general, all but the most trivial of Ada routines are going to require some support from the internal Ada runtime library. __gnat_rcheck_CE_Overflow_Check certainly sounds like one of those. (My SWAG for an English translation of that is "Gnat Runtime check for constraint_error exceptions on an object going out of the defined bounds of its subtype").

If your main program is in Ada, then you get the RTL linked in automatically, along with startup elaboration code generated for any packages that may need it, and shutdown cleanup code. If your main program is in some other language, then you usually will need to link those in manually, and find a way to call elaboration manually before your Ada routine is called.

Getting any more specific involves the details of linking and running in a mixed-language environment, which is (last I checked) not entirely language-defined. You did specify your compiler, but it might also be helpful if you were to specify what platform you are trying this on.

For example, for Windows with Gnat, the relevant documentation is the section on Mixed-Language Programming Under Windows, from the Gnat User's Guide.

One thing I'm noticing in particular is that I don't see anything in your C main that looks like its making the calls to adainit() and adafinal() I see in the relevant section of those docs.

Unable to link C source code with Ada static library (Error: libnewapi.a(unit1.o):unit1.adb:undefined reference to `__gnat_rcheck_CE_Overflow_Check')

1 Answers1