Link object file to project with gprbuild

Question

Using nvcc I created an object file from my project with the following bash script:

nvcc -Xcompiler -std=c99 -dc src/interface.cu src/functions.cu
nvcc -dlink interface.o functions.o -o obj/link.o

In my obj folder I get a link.o file. I need to link this file to my Ada project using gprbuild. I can compile an Ada-Cuda project perfectly if I don't use the separate compilation mode of nvcc. But now, as I need the separate compilation mode, I have to find a way to link link.o with the rest of the project. This is the .gpr file:

project Test is
    for Languages use ("Ada");
    for Source_Dirs use ("src");
    for Object_Dir use "obj";
    for Exec_Dir use ".";

    for Main use ("main.adb");

    for Create_Missing_Dirs use "True";

    package Linker is
        for Default_Switches("Ada") use (
            "-L/usr/local/cuda/lib64",
            "-lcuda",
            "-lcudart",
            "-lcudadevrt",
            "-lstdc++",
            "-lm");

        for Leading_Switches("Ada") use (
            "link.o" -- Doesn't work
            );
    end Linker;
end Test;

This is the error I get

Bind
   [gprbind]      main.bexch
   [Ada]          main.ali
Link
   [link]         main.adb
/usr/local/opt/gnat-19.1-x86_64/bin/../libexec/gcc/x86_64-pc-linux-gnu/7.3.1/ld: main.o: in function `_ada_main':
main.adb:(.text+0x5): undefined reference to `bind_say_hello'
/usr/local/opt/gnat-19.1-x86_64/bin/../libexec/gcc/x86_64-pc-linux-gnu/7.3.1/ld: link.o: in function `__cudaRegisterLinkedBinary_45_tmpxft_0000404a_00000000_11_interface_cpp1_ii_f804fc64':
link.stub:(.text+0x50): undefined reference to `__fatbinwrap_45_tmpxft_0000404a_00000000_11_interface_cpp1_ii_f804fc64'
/usr/local/opt/gnat-19.1-x86_64/bin/../libexec/gcc/x86_64-pc-linux-gnu/7.3.1/ld: link.o: in function `__cudaRegisterLinkedBinary_45_tmpxft_0000404a_00000000_13_functions_cpp1_ii_e57d67fc':
link.stub:(.text+0x96): undefined reference to `__fatbinwrap_45_tmpxft_0000404a_00000000_13_functions_cpp1_ii_e57d67fc'
collect2: error: ld returned 1 exit status
gprbuild: link of main.adb failed
gprbuild: failed command was: /usr/local/opt/gnat-19.1-x86_64/bin/gcc main.o link.o b__main.o -L/usr/local/cuda/lib64 -lcuda -lcudart -lcudadevrt -lstdc++ -lm -L/home/cir_eti/Documents/test/multi_cu_file/obj/ -L/home/cir_eti/Documents/test/multi_cu_file/obj/ -L/usr/local/opt/gnat-19.1-x86_64/lib/gcc/x86_64-pc-linux-gnu/7.3.1/adalib/ -static-libgcc /usr/local/opt/gnat-19.1-x86_64/lib/gcc/x86_64-pc-linux-gnu/7.3.1/adalib/libgnat.a -ldl -Wl,-rpath-link,/usr/local/opt/gnat-19.1-x86_64/lib/gcc/x86_64-pc-linux-gnu/7.3.1//adalib -Wl,-z,origin,-rpath,/usr/local/cuda/lib64:$ORIGIN/obj:/usr/local/opt/gnat-19.1-x86_64/lib/gcc/x86_64-pc-linux-gnu/7.3.1/adalib -o /home/cir_eti/Documents/test/multi_cu_file//main

Unsure if gprbuild supports adding .o files. Would compiling with --lib to an .a file and then simply linking that with gprbuild solve the problem? — flyx
Adding -v to the link args may show what it's doing with for Object_Dir use "obj"; and "link.o" which may show why it's not putting them together and finding your file. The actual linker command line is probably useful too. — user_1818839
Haven’t used Linker’Leading_Switches. I’d be inclined to put link.o as the first entry in Linker’Default_Switches. — Simon Wright
It seems that 'link.o' is being passed to the linker, according to the error message. The problem should be elsewhere, for example, some missing library. — Gneuromante
So the problem was really simple... Adding just link.o wasn't enough (it contains only GPU code). I also had to link interface.o and functions.o. As adviced by @flyx I created a static library with all the .o needed in it. It works like a charm now — Louis Etienne

Shark8 Shark8 · Accepted Answer · 2021-03-30T21:19:54

I'm doing an interface to a DLL and the interface they give is via a C header-file, I have an autogenerated package from the spec; I'm adding the post-conditions and, in the private portion of the package, I put this Linker_Options pragma which instructs the linker to interface with the DLL. -- IIUC, you could use this to address your problem.

Package import_example is

    Bad_Return           : Exception;

    SUCCESS              : constant := 20007;
    NOT_INITIALIZED      : constant := 20008;
    ERROR                : constant := 20009;
    INVALID              : constant := 20010;

    Function Return_Report (Name : String; Value : unsigned ) return String is
        (Name & " should not return" & unsigned'Image(Value) & '.') with Inline;

    function item_1 return unsigned  -- some_c_header.h:249
      with Import   => True, 
      Convention    => C, 
      External_Name => "item_1",
      Post          => item_1'Result in
        SUCCESS | NOT_INITIALIZED | ERROR | INVALID
          or else raise Bad_Return with
            Return_Report("item_1", item_1'Result)
    ;

    function wait return unsigned  -- some_c_header.h:250
      with Import   => True, 
      Convention    => C, 
      External_Name => "wait",
      Post          => wait'Result in
        SUCCESS | NOT_INITIALIZED | ERROR 
          or else raise Bad_Return with
            Return_Report("wait", wait'Result)
    ;

Private
    Pragma Linker_Options( "-lsmcex" );
End import_example;

Link object file to project with gprbuild

1 Answers