fix Issue 22744 - ImportC: builtins defined in __builtins.di cause un…

[WalterBright]

…defined symbol linker errors

Making them templates makes the import "header only".

[dlang-bot]

Thanks for your pull request, @WalterBright!

Bugzilla references

Auto-close	Bugzilla	Severity	Description
✓	22744	normal	ImportC: builtins defined in __builtins.di cause undefined symbol linker errors.

Testing this PR locally

If you don't have a local development environment setup, you can use Digger to test this PR:

dub run digger -- build "master + druntime#3732"

[WalterBright]

Test compilable/test6461.sh failed. The logged output:
 ... compilable\test67.d            ()
D:\a\1\dmd\test\test_results\compilable\test6461a.lib: Error: MS-Coff object module `a.obj` has magic = 6202, should be 8664
D:\a\1\dmd\test\test_results\compilable\test6461a.lib: Error: MS-Coff object module `a_1_149.obj` has magic = 6202, should be 8664
D:\a\1\dmd\test\test_results\compilable\test6461a.lib: Error: MS-Coff object module `tmpl_2_309.obj` has magic = 6202, should be 8664
D:\a\1\dmd\test\test_results\compilable\test6461a.lib: Error: MS-Coff object module `object_3_5ad.obj` has magic = 6202, should be 8664
D:\a\1\dmd\test\test_results\compilable\test6461a.lib: Error: MS-Coff object module `object_4_9ff.obj` has magic = 6202, should be 8664
D:\a\1\dmd\test\test_results\compilable\test6461a.lib: Error: MS-Coff object module `object_5_5e9.obj` has magic = 6202, should be 8664

It makes no sense that this has anything to do with this PR.

[WalterBright]

@RazvanN7 is there something else in druntime causing these errors?

[RazvanN7]

Do you have the latest version of druntime? @MoonlightSentinel has been doing some MS-Coff patches recently so there might be some branch checkout mismatches.

[WalterBright]

trying a rebase...

[RazvanN7]

That seems to have fixed it. When in doubt, rebase...

[huglovefan]

this might be a separate issue but it still causes a link error if you use dmd -i (include-imports mode)

% cat main.c
int main() { double x = __builtin_inf(); }
% work/result/bin/dmd -run main.c
% work/result/bin/dmd -i -run main.c
ld.lld: error: undefined symbol: _D10__builtins__T13__builtin_infZQqFNaNbNiNfZd
>>> referenced by main.c
>>>               main.o:(main)
clang-12: error: linker command failed with exit code 1 (use -v to see invocation)
Error: linker exited with status 1

same thing affects D code if you have templates in a .di file and use -i

edit: reported at https://issues.dlang.org/show_bug.cgi?id=22750

[WalterBright]

@huglovefan as issue is not specific to this PR or ImportC, please file a bugzilla issue for it.