Static linking with a .lib file not working

[Aquachains]

If i statically link a nim application with a .lib file, i get an error output.

Example

foo.nim

proc add*(a, b: int): int {.cdecl, exportc.} =
    a + b
proc sub*(a, b: int): int {.cdecl, exportc.} =
    a - b

Build with nim c --app:staticlib foo.nim to generate the "foo.lib" file.

main.nim

{.passL:"foo.lib".}
proc add*(a, b: int):int {.cdecl, importc.}
proc sub*(a, b: int):int {.cdecl, importc.}

echo add(10, 5)
echo sub(10, 5)

Build and run with nim c -r main.nim

Current Output

P:\Nim\LearnCBinding>nim c -r main.nim
Hint: used config file 'C:\nim-1.5.1\config\nim.cfg' [Conf]
Hint: used config file 'C:\nim-1.5.1\config\config.nims' [Conf]
....CC: stdlib_io.nim
CC: stdlib_system.nim
CC: main.nim

Hint:  [Link]
foo.lib(@mfoo.nim.c.o):@mfoo.nim.c:(.text+0x1f6): multiple definition of `PreMainInner'
C:\Users\Peter\nimcache\main_d\@mmain.nim.c.o:@mmain.nim.c:(.text+0x120): first defined here
foo.lib(@mfoo.nim.c.o):@mfoo.nim.c:(.text+0x20a): multiple definition of `PreMain'
C:\Users\Peter\nimcache\main_d\@mmain.nim.c.o:@mmain.nim.c:(.text+0x134): first defined here
foo.lib(@mfoo.nim.c.o):@mfoo.nim.c:(.text+0x240): multiple definition of `NimMainInner'
C:\Users\Peter\nimcache\main_d\@mmain.nim.c.o:@mmain.nim.c:(.text+0x16f): first defined here
foo.lib(@mfoo.nim.c.o):@mfoo.nim.c:(.text+0x254): multiple definition of `NimMain'
C:\Users\Peter\nimcache\main_d\@mmain.nim.c.o:@mmain.nim.c:(.text+0x183): first defined here
foo.lib(@mfoo.nim.c.o):@mfoo.nim.c:(.text+0x285): multiple definition of `main'
C:\Users\Peter\nimcache\main_d\@mmain.nim.c.o:@mmain.nim.c:(.text+0x1b4): first defined here
foo.lib(@mfoo.nim.c.o):@mfoo.nim.c:(.text+0x2da): multiple definition of `NimMainModule'
C:\Users\Peter\nimcache\main_d\@mmain.nim.c.o:@mmain.nim.c:(.text+0x209): first defined here
collect2.exe: error: ld returned 1 exit status
Error: execution of an external program failed: 'C:\nim-1.5.1\dist\mingw64\bin\gcc.exe   -o P:\Nim\LearnCBinding\main.exe  C:\Users\Peter\nimcache\main_d\stdlib_io.nim.c.o C:\Users\Peter\nimcache\main_d\stdlib_system.nim.c.o C:\Users\Peter\nimcache\main_d\@mmain.nim.c.o  foo.lib   '

Expected Output

15
-5

Possible Solution

Because of the error "mulitple definition of" the nim compiler should exclude runtime specific code in libraries. But i could also not link to a static .lib of a third party library. There could be a general problem with static linking.

Additional Information

Tested with Nim version 1.5.1, Windows 10 and reinstalled MingW.
I firstly reported this problem here: https://stackoverflow.com/questions/64677151/nim-use-a-static-library
Then here: https://forum.nim-lang.org/t/7080.
I tried the parameter --dynlibOverride:foo and --noMain:on
and also the pragma {.link: "foo.lib", passc:"-L foo".}
If i add the dynlib pragma to both files and create a .dll file with nim c --app:lib foo.nim it just works.

Thanks for every help.

[shirleyquirk]

One workaround is to instruct the linker to ignore the multiple definitions.
This will of course be highly platform-specific, does nothing to address the root problem, while possibly silently causing more. but here you go:
using gnu ld 2.35.1 and gcc on linux i was able to make the example work by changing main.nim to:

{.passL:"libfoo.a -Wl,--allow-multiple-definition".}
...

[timotheecour]

Is it normal to generate Main symbol on lib & staticlib compilation ?

yes, see why here https://nim-lang.github.io/Nim/backends.html#interfacing-backend-code-calling-nim

The Nim compiler can generate a C interface header through the --header command-line switch. The generated header will contain all the exported symbols and the NimMain proc which you need to call before any other Nim code.

• note: the same bug affects posix (eg: osx)

• see fix #15955: avoid duplicate symbol errors with --app:staticlib by using weak symbols #16945, please test against that PR (I only have OSX, hard to test on windows)

pass --app:staticlib -d:nimLinkerWeakSymbols --nomain (see tests/misc/tapp_lib_staticlib.nim)

EDIT: works on posix, not yet on windows

[Clonkk]

Works on Linux with a warning on the C code generated :

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Compilation Line :
../../Nim/bin/nim c --app:staticlib --noMain:on -d:nimLinkerWeakSymbols --clearNimblePath --skipCfg --skipUserCfg --skipProjCfg --skipParentCfg foo.nim
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
....
CC: stdlib_system.nim
CC: foo.nim
/home/sidger/.cache/nim/foo_d/stdlib_system.nim.c: In function ‘sysFatal__27U3EueEEOKabXYRrgiy5Asystem’:
/home/sidger/.cache/nim/foo_d/stdlib_system.nim.c:4517:1: warning: ‘noreturn’ function does return
 4517 | }
      | ^
/home/sidger/.cache/nim/foo_d/stdlib_system.nim.c: In function ‘sysFatal__pO9abt7E7FWB3DInHeLgZeQsystem’:
/home/sidger/.cache/nim/foo_d/stdlib_system.nim.c:4738:1: warning: ‘noreturn’ function does return
 4738 | }
      | ^
Hint:  [Link]
Hint: 14658 lines; 0.422s; 20.41MiB peakmem; Debug build; proj: /home/sidger/Workspace/Nim/BugStaticLib/static_linking_bug/static/foo.nim; out: /home/sidger/Workspace/Nim/BugStaticLib/static_linking_bug/static/libfoo.a [SuccessX]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Compilation Line :
../../Nim/bin/nim c -r -d:nimLinkerWeakSymbols static_main.nim
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Hint: used config file '/home/sidger/Workspace/Nim/BugStaticLib/Nim/config/nim.cfg' [Conf]
Hint: used config file '/home/sidger/Workspace/Nim/BugStaticLib/Nim/config/config.nims' [Conf]
Hint: used config file '/home/sidger/Workspace/Nim/BugStaticLib/static_linking_bug/static/config.nims' [Conf]
....
Hint:  [Link]
Hint: 30111 lines; 0.210s; 31.703MiB peakmem; Debug build; proj: /home/sidger/Workspace/Nim/BugStaticLib/static_linking_bug/static/static_main.nim; out: /home/sidger/Workspace/Nim/BugStaticLib/static_linking_bug/static/static_main [SuccessX]
Hint: /home/sidger/Workspace/Nim/BugStaticLib/static_linking_bug/static/static_main  [Exec]

I'll see if I can test on Windows later

[Clonkk]

Commit c79bde74a50bc54b9c1d1c968761b3a81a4c4d0e does not show the warning on Linux and works as expected.

Windows doesn't compile on the other hand. I used gcc.exe from MinGW. Here are the versions :

PS C:\Users\sidger\Workspace\staticLibBug\Nim> .\bin\nim.exe -v
Nim Compiler Version 1.5.1 [Windows: i386]
Compiled at 2021-02-10
Copyright (c) 2006-2021 by Andreas Rumpf

git hash: c79bde74a50bc54b9c1d1c968761b3a81a4c4d0e
active boot switches: -d:release

PS C:\Users\sidger\Workspace\staticLibBug\Nim> gcc.exe --version
gcc.exe (MinGW.org GCC-6.3.0-1) 6.3.0
Copyright (C) 2016 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

The error message on powershell is rather long so I put it into a text file :

..\..\Nim\bin\nim.exe build 3>&1 2>&1 > windows_pr_fix_15955_log.txt

windows_pr_fix_15955_log.txt

Here's a preview because it basically repeat the same message on different places :

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
../../Nim/bin/nim c --app:staticlib --noMain:on -d:nimLinkerWeakSymbols --clearNimblePath --skipCfg --skipUserCfg --skipProjCfg --skipParentCfg foo.nim
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
CC: stdlib_io.nim
CC: stdlib_system.nim
CC: foo.nim
..\..\Nim\bin\nim.exe : ....C:\Users\sidger\nimcache\foo_d\stdlib_io.nim.c:42:1: error: 'selectany' attribute applies only to initialized variables with external linkage
Au caractère Ligne:1 : 1
+ ..\..\Nim\bin\nim.exe build 3>&1 2>&1 > windows_pr_fix_15955_log.txt
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    + CategoryInfo          : NotSpecified: (....C:\Users\si...xternal linkage:String) [], RemoteException
    + FullyQualifiedErrorId : NativeCommandError
 
 N_LIB_PRIVATE N_NOINLINE(void, callDepthLimitReached__mMRdr4sgmnykA9aWeM9aDZlw)(void);
 ^~~~~~~~~~~~~
C:\Users\sidger\nimcache\foo_d\stdlib_io.nim.c:76:1: error: 'selectany' attribute applies only to initialized variables with external linkage
 N_LIB_PRIVATE N_NIMCALL(void, stdlib_ioInit000)(void) {
 ^~~~~~~~~~~~~

Error: execution of an external compiler program 'gcc.exe -c    -IC:\Users\sidger\Workspace\staticLibBug\Nim\lib -IC:\Users\sidger\Workspace\staticLibBug\static_linking_bug\static -o 
C:\Users\sidger\nimcache\foo_d\stdlib_io.nim.c.o C:\Users\sidger\nimcache\foo_d\stdlib_io.nim.c' failed with exit code: 1


C:\Users\sidger\nimcache\foo_d\@mfoo.nim.c:38:1: error: 'selectany' attribute applies only to initialized variables with external linkage
 N_LIB_PRIVATE N_CDECL(NI, add)(NI a, NI b);
 ^~~~~~~~~~~~~
C:\Users\sidger\nimcache\foo_d\@mfoo.nim.c:39:1: error: 'selectany' attribute applies only to initialized variables with external linkage
 N_LIB_PRIVATE N_NOINLINE(void, raiseOverflow)(void);
 ^~~~~~~~~~~~~
C:\Users\sidger\nimcache\foo_d\@mfoo.nim.c:41:1: error: 'selectany' attribute applies only to initialized variables with external linkage
 N_LIB_PRIVATE N_NOINLINE(void, callDepthLimitReached__mMRdr4sgmnykA9aWeM9aDZlw)(void);
 ^~~~~~~~~~~~~
C:\Users\sidger\nimcache\foo_d\@mfoo.nim.c:43:1: error: 'selectany' attribute applies only to initialized variables with external linkage
 N_LIB_PRIVATE N_CDECL(NI, sub)(NI a, NI b);
 ^~~~~~~~~~~~~
C:\Users\sidger\nimcache\foo_d\@mfoo.nim.c:45:1: error: 'selectany' attribute applies only to initialized variables with external linkage
 N_LIB_PRIVATE N_NOINLINE(void, nimGC_setStackBottom)(void* theStackBottom);
 ^~~~~~~~~~~~~

Hope that helps you !

[waruqi]

I am trying to let xmake support building nim projects, xmake-io/xmake#1756

I also encountered a similar problem when compiling and generating static libraries. I also very much hope that this problem can be resolved.

But I now have a workaround solution, which is temporarily compatible and fixed, and I can successfully link the static library.

we can set "--passC:-DNimMain=NimMain_xxx" to rename _NimMain to avoid redefine conflict when we are building static libraries.

function buildargv(self, sourcefiles, targetkind, targetfile, flags)
    local flags_extra = {}
    if targetkind == "static" then
        -- fix multiple definition of `NimMain', it is only workaround solution
        -- we need to wait for this problem to be resolved
        --
        -- @see https://github.com/nim-lang/Nim/issues/15955
        local uniquekey = hash.uuid(targetfile):split("-", {plain = true})[1]
        table.insert(flags_extra, "--passC:-DNimMain=NimMain_" .. uniquekey)
        table.insert(flags_extra, "--passC:-DNimMainInner=NimMainInner_" .. uniquekey)
        table.insert(flags_extra, "--passC:-DNimMainModule=NimMainModule_" .. uniquekey)
        table.insert(flags_extra, "--passC:-DPreMain=PreMain_" .. uniquekey)
        table.insert(flags_extra, "--passC:-DPreMainInner=PreMainInner_" .. uniquekey)
    end
    return self:program(), table.join("c", flags, flags_extra, "-o:" .. targetfile, sourcefiles)
end

see https://github.com/xmake-io/xmake/blob/ae65d03b29b506c5cc7122214d9eb81ad1efdbcc/xmake/modules/core/tools/nim.lua#L102-L117

Now can we successfully compile and link it.

$ xmake -v
[ 33%]: linking.release libfoo.a
/usr/local/bin/nim c --opt:speed --nimcache:build/.gens/foo/macosx/x86_64/release/nimcache --app
:staticlib --noMain --passC:-DNimMain=NimMain_B6D5BD02 --passC:-DNimMainInner=NimMainInner_B6D5B
D02 --passC:-DNimMainModule=NimMainModule_B6D5BD02 --passC:-DPreMain=PreMain_B6D5BD02 --passC:-D
PreMainInner=PreMainInner_B6D5BD02 -o:build/macosx/x86_64/release/libfoo.a src/foo.nim
[ 66%]: linking.release test
/usr/local/bin/nim c --opt:speed --nimcache:build/.gens/test/macosx/x86_64/release/nimcache --pa
ssL:-Lbuild/macosx/x86_64/release --passL:-lfoo -o:build/macosx/x86_64/release/test src/main.nim
[100%]: build ok!

[zer0pwned]

I'm having the same issue and seems like the nim developers do not indent to resolve this (I guess it is more or less a linking issue rather than nim issue). Such a bummer I cannot use nim to generate a static binary library where other nim developer can use it.

[Araq]

The issue is open and PRs to fix it are welcome.

[Clonkk]

@timotheecour had commits that fixed this if I remember correctly.

Maybe his work could be merged?

[deech]

I am also hitting this, I have a static archive generated with the CPP backend that externs some functions to be used with a program written with the C backend, both have NimMain, PreMain etc and so fails to link the executable. I can use -DPreMainInner=... workaround above because I don't think I'm using any stdlib modules with global initialization but if they do I'm blocked. A killer feature of Nim would be a way of easily packaging a library into a shared/static library that could be called from other languages.

[Araq]

Maybe his work could be merged?

Got a link handy?

[ghost]

@Araq I think they were mentioning #16945 which is still in a draft state it seems like

[ringabout]

related: #19830

It wasn't fixed. It is still broken with 1.6.6.

[deech]

Compiling to CPP with a namespace addressed the immediate problem. The real fix as mentioned in the linked issue is to have the compiler add prefixes to visible symbols. However looking through the compiler this seems like a daunting change.