Static Library output with Odin

[herohiralal]

I have a C++ project and I'd like to expose an Odin API. For that I would like to link statically.

So I have a few different questions, that I'd appreciate if someone can help answer.

1. I looked up -build-mode in compiler docs. Is -build-mode:obj enough to create a static library (*.lib file on Windows, *.a file on *nix)?
2. All my bindings will be generated by an external tool, so is it possible to use absolute paths with foreign import "C:\tmp\MyCoolFile.lib"? Is it possible to entirely ignore this part, since I only need a static library and will link manually?

[herohiralal]

Providing some more info. Directly using -build-mode:obj doesn't seem to work as it still declares a main symbol.

Here's the C++ file:

// main.cpp
#include <iostream>

extern "C" int UncoolMul(int a, int b)
{
    return a * b;
}

extern "C" {
    int CoolAdd(int a, int b);
    int CoolMul(int a, int b);
}

int main(int argc, char* argv[])
{
    std::cout << "Hello, OdinLinkTest!\n";
    std::cout << CoolAdd(3, 4);
    return 0;
}

Here's the Odin file:

// main.odin
package main

import "core:fmt"

CoolAdd :: proc "c" (a: i32, b: i32) -> i32 {
	return a + b
}

foreign {
    UncoolMul :: proc "c" (a: i32, b: i32) -> i32 ---
}

CoolMul :: proc "c" (a: i32, b: i32) -> i32 {
    return UncoolMul(a, b)
}

Odin code compiled with:

odin build main.odin -file -build-mode:obj -out:./kk.obj -target:windows_amd64

Modified Visual C++ Project:

  <ItemDefinitionGroup>
    <Link>
      <AdditionalDependencies>kk.obj;%(AdditionalDependencies)</AdditionalDependencies>
      <AdditionalLibraryDirectories>$(SolutionDir)Linked/;%(AdditionalLibraryDirectories)</AdditionalLibraryDirectories>
    </Link>
  </ItemDefinitionGroup>

Here's the C++ compiler output:

0>------- Started building project: OdinLinkTest
C:\Program Files\Microsoft Visual Studio\2022\Community\VC\Tools\Llvm\x64\bin\lld-link.exe /OUT:"D:\Projects\C++\OdinLinkTest\x64\Debug\OdinLinkTest.exe" /INCREMENTAL /LIBPATH:D:\Projects\C++\OdinLinkTest\Linked/ kk.obj kernel32.lib user32.lib gdi32.lib winspool.lib comdlg32.lib advapi32.lib shell32.lib ole32.lib oleaut32.lib uuid.lib odbc32.lib odbccp32.lib /MANIFEST /MANIFESTUAC:"level='asInvoker' uiAccess='false'" /manifest:embed /DEBUG:FULL /PDB:"D:\Projects\C++\OdinLinkTest\x64\Debug\OdinLinkTest.pdb" /SUBSYSTEM:CONSOLE /DYNAMICBASE /NXCOMPAT /IMPLIB:"D:\Projects\C++\OdinLinkTest\x64\Debug\OdinLinkTest.lib"  x64\Debug\OdinLinkTest.obj
0>lld-link: Error  : duplicate symbol: main
>>> defined at D:\Projects\C++\OdinLinkTest\Linked/kk.obj
>>> defined at x64\Debug\OdinLinkTest.obj
0>------- Finished building project: OdinLinkTest. Succeeded: False. Errors: 1. Warnings: 0
Build completed in 00:00:01.630

[Kelimion]

You can add -no-entry-point if you don't want to export main.

[herohiralal]

This works. Need to also add @export attribute to any function that you want to not be mangled.

[herohiralal]

Posting the complete solution here.

First, some info:

A .LIB file is a collection of .OBJ files concatenated together with an index. There should be no difference in how the linker treats either.

source

Here's the C++ file:

// main.cpp
#include <iostream>

extern "C" int UncoolMul(int a, int b)
{
    return a * b;
}

extern "C" {
    int CoolAdd(int a, int b);
    int CoolMul(int a, int b);
}

int main(int argc, char* argv[])
{
    std::cout << CoolAdd(3, 4) << '\n';
    std::cout << CoolMul(3, 4) << '\n';
    return 0;
}

Here's the Odin file:

// kk.odin
package main

import "core:fmt"

@export
CoolAdd :: proc "c" (a: i32, b: i32) -> i32 {
	return a + b
}

foreign {
    UncoolMul :: proc "c" (a: i32, b: i32) -> i32 ---
}

@export // CRITICAL - works similar to `#[no_mangle] in rust ffi`
CoolMul :: proc "c" (a: i32, b: i32) -> i32 {
    return UncoolMul(a, b)
}

Odin code compiled with:

odin build main.odin -file -build-mode:obj -out:./kk.obj -target:windows_amd64 -no-entry-point

Modified Visual C++ Project (*.vcxproj file):

  <ItemDefinitionGroup>
    <Link>
      <AdditionalDependencies>kk.obj;%(AdditionalDependencies)</AdditionalDependencies>
      <AdditionalLibraryDirectories>$(SolutionDir)Linked/;%(AdditionalLibraryDirectories)</AdditionalLibraryDirectories>
    </Link>
  </ItemDefinitionGroup>