Bug 23837 – importc fails to link on windows x86 but successes on x64

main.d: import test; struct TexturePacker { stbrp_context _context; } void main() { auto res = TexturePacker(); } test.c: struct stbrp_context { int width; int height; int align; int init_mode; int heuristic; }; it works on x86_64, but on x86_mscoff it fails with: error: undefined symbol: __C.stbrp_context.__inittest

What's the command you use to compile it?

dmd main.d -m32

The `__init{struct name}` symbol is generated as the initializer for a struct by the dmd.tocsym.toInitializer() function. It is inserted into the object file generated for the source file with the struct definition in it. Hence, dmd -m32 main.d will fail to link, because the object file for test.c is not linked in. To fix, dmd -m32 main.d test.c So why does the former still work on other platforms? If the struct is zero initialized, a section in the BSS segment of all zeros is used instead. But the relocations for BSS do not work for MSCOFF-32. Since C structs are always default initialized to zero, a better solution would be to initialize the instance with code rather than copying zero'd data to it.

@WalterBright created dlang/dmd pull request #15126 "fix Issue 23837 - importc fails to link on windows x86 but successes …" fixing this issue: - fix Issue 23837 - importc fails to link on windows x86 but successes on x64 https://github.com/dlang/dmd/pull/15126

dlang/dmd pull request #15126 "fix Issue 23837 - importc fails to link on windows x86 but successes …" was merged into master: - 0159114c5b907268c6edc1ab042bb2ac576f54c9 by Walter Bright: fix Issue 23837 - importc fails to link on windows x86 but successes on x64 https://github.com/dlang/dmd/pull/15126