[LLD][COFF] undefined section symbol is not being handled correctly

[NikitaSmith057]

dll.c

__declspec(dllexport) void foo() {}

main.c

extern char __IMPORT_DESCRIPTOR_dll;
int main()
{
   // force linker to pull in archive member with undefined section symbols
   void *p = &__IMPORT_DESCRIPTOR_dll;
}

Build Steps

1. cl /c dll.c
2. link /dll dll.obj
3. cl /c main.c
4. lld-link dll.lib main.obj

Error: lld-link: error: section larger than 4 GiB: .data

I think lld misinterprets these symbols in dll.lib, the symbol values are actually section flags that linker is supposed to match with resolved .idata$4 and .idata$5.

...
004 C0000040 UNDEF  notype       Section      | .idata$4
005 C0000040 UNDEF  notype       Section      | .idata$5
...

Linking in step 2 with lld produces a different error: lld-link: error: dll.lib(dll.dll): .idata$4 should not refer to special section 0

[llvmbot]

@llvm/issue-subscribers-lld-coff

Author: Nikita (NikitaSmith057)

### dll.c ```C __declspec(dllexport) void foo() {} ``` ### main.c ```C extern char __IMPORT_DESCRIPTOR_dll; int main() { // force linker to pull in archive member with undefined section symbols void *p = &__IMPORT_DESCRIPTOR_dll; } ``` ### Build Steps 1. `cl /c dll.c` 2. `link /dll dll.obj` 3. `cl /c main.c` 4. `lld-link dll.lib main.obj`

Error: lld-link: error: section larger than 4 GiB: .data

I think lld misinterprets these symbols in dll.lib, the symbol values are actually section flags that linker is supposed to match with resolved .idata$4 and .idata$5.

...
004 C0000040 UNDEF  notype       Section      | .idata$4
005 C0000040 UNDEF  notype       Section      | .idata$5
...

Linking in step 2 with lld produces a different error: lld-link: error: dll.lib(dll.dll): .idata$4 should not refer to special section 0

[mstorsjo]

This sounds very much like what was fixed in #122811 and #123916; that fix should be included in the 20.x releases. I can reproduce this issue with 19.x but not with 20.x.

[NikitaSmith057]

Can confirm, I tried latest release and this issue was fixed there.