builtin: link user32 for boehm GC on Windows

[zeozeozeo]

Before this commit, V didn't link with user32 on Windows for compilers other than tcc, so the MessageBoxA call in gcboehm was an unresolved symbol.
This fixes #20724.

[spytheman]

Does that happen only on a 32bit windows?

For me, on win11, 64bit, with clang from winlibs.com:

[spytheman]

Hm, the issue says that you are working in a 64bit windows environment 🤔, weird.

[spytheman]

The above used this to compile the GC code in thirdparty\libgc\gc.c:

clang -std=c99 -D_DEFAULT_SOURCE   -fwrapv  -D GC_NOT_DLL=1 -D GC_WIN32_THREADS=1 \
-D GC_BUILTIN_ATOMIC=1 -D GC_THREADS=1 -I "D:\programs\v\thirdparty\libgc\include" \
-o "C:\Users\delia\.vmodules\cache\15\15b737768ed213bcb57ac57f6af5d433.module.builtin.o" \
-c "D:\programs\v\thirdparty\libgc\gc.c"

which also passed for me without warnings.

[spytheman]

What is your clang version @zeozeozeo ?

[zeozeozeo]

What is your clang version @zeozeozeo ?

clang version 18.1.0rc
Target: x86_64-pc-windows-msvc
Thread model: posix

[spytheman]

Can you please try this separately, in the root folder of the project:

clang -std=c99 -D_DEFAULT_SOURCE -fwrapv  -D GC_NOT_DLL=1 -D GC_WIN32_THREADS=1 \
-D GC_BUILTIN_ATOMIC=1 -D GC_THREADS=1 -I "thirdparty\libgc\include" \ 
-c "thirdparty\libgc\gc.c" \
-o x.o

[zeozeozeo]

Can you please try this separately, in the root folder of the project:

clang -std=c99 -D_DEFAULT_SOURCE -fwrapv  -D GC_NOT_DLL=1 -D GC_WIN32_THREADS=1 \
-D GC_BUILTIN_ATOMIC=1 -D GC_THREADS=1 -I "thirdparty\libgc\include" \ 
-c "thirdparty\libgc\gc.c" \
-o x.o

this works and outputs the x.o file with 32 warnings (https://pastebin.com/8s6qQCr6)

[zeozeozeo]

I use the clang bundled with LLVM: https://github.com/llvm/llvm-project/releases
Perhaps using clang from winlibs.com would fix this issue

[spytheman]

I use the clang bundled with LLVM: https://github.com/llvm/llvm-project/releases Perhaps using clang from winlibs.com would fix this issue

Yes, I can confirm, it fails with clang from the official release:

d:\programs\v\aaa>clang --version
(built by Brecht Sanders, r5) clang version 17.0.6
Target: x86_64-w64-windows-gnu
Thread model: posix
InstalledDir: d:/programs/mingw64/bin

d:\programs\v\aaa>
d:\programs\v\aaa>d:\programs\LLVM\bin\clang.exe --version
clang version 18.1.0rc
Target: x86_64-pc-windows-msvc
Thread model: posix
InstalledDir: d:\programs\LLVM\bin

d:\programs\v\aaa>
d:\programs\v\aaa>v -cc clang .

d:\programs\v\aaa>
d:\programs\v\aaa>
d:\programs\v\aaa>v -cc d:\programs\LLVM\bin\clang.exe .
==================
D:\programs\v\aaa\aaa.exe : fatal error LNK1120: 1 unresolved externals
clang: error: linker command failed with exit code 1120 (use -v to see invocation)
...
==================
(Use `v -cg` to print the entire error message)

builder error:
==================
C error. This should never happen.

This is a compiler bug, please report it using `v bug file.v`.

https://github.com/vlang/v/issues/new/choose

You can also use #help on Discord: https://discord.gg/vlang


d:\programs\v\aaa>

[spytheman]

With the change in this PR, it works with the LLVM's clang too.

Excellent work.