| Issue |
128706
|
| Summary |
lld-link.exe fails to find DATA imports without __declspec(dllimport)
|
| Labels |
new issue
|
| Assignees |
|
| Reporter |
stasoid
|
clang/lld-link version: 19.1.0.
This issue was encountered while porting Ladybird to Windows. Ladybird discord discussions: [one](https://discord.com/channels/1247070541085671459/1306918361732616212/1339658967214723112) [two](https://discord.com/channels/1247070541085671459/1306918361732616212/1343462676839530538).
If data item (global or class static variable) is imported, lld-link refuses to link it unless `__declspec(dllimport)` is specified. Functions (global and member functions) don't have this problem. See also: [WINDOWS_EXPORT_ALL_SYMBOLS](https://cmake.org/cmake/help/latest/prop_tgt/WINDOWS_EXPORT_ALL_SYMBOLS.html) in CMake.
I don't know if it is a bug or a feature, I could not find a similar issue. Is lld-link intentionally matches the behavior of Visual Studio link.exe here? It would be great if it behaved like on Linux instead. This is just confusing.
Simplified reproduction:
mylib.h:
```cpp
struct A
{
static int static_member; // error
void member_function(); // OK
};
extern int global; // error
void global_function(); // OK
```
mylib.cpp:
```cpp
#include "mylib.h"
int global;
int A::static_member;
void global_function()
{
}
void A::member_function()
{
}
```
myprog.cpp:
```cpp
#include "mylib.h"
int main()
{
global = 1;
global_function();
A::static_member = 1;
A().member_function();
}
```
build.bat:
```cmd
:: create dll.o
clang -c mylib.cpp
:: create exports.def
echo mylib.o > objs
cmake -E __create_def exports.def objs
:: create mylib.dll and mylib.lib
lld-link mylib.o /dll libcmt.lib /DEF:exports.def
:: create myprog.o
clang -c myprog.cpp
:: create myprog.exe
lld-link myprog.o mylib.lib libcmt.lib
```
The last command fails with these errors:
```
lld-link: error: undefined symbol: int global
>>> referenced by myprog.o:(main)
lld-link: error: undefined symbol: public: static int A::static_member
>>> referenced by myprog.o:(main)
```
The def/lib/dll export all 4 symbols:
```
> cat exports.def
EXPORTS
?global@@3HA DATA
?static_member@A@@2HA DATA
?global_function@@YAXXZ
?member_function@A@@QEAAXXZ
> dumpbin /exports mylib.lib
(some output skipped)
?global@@3HA (int global)
?global_function@@YAXXZ (void __cdecl global_function(void))
?member_function@A@@QEAAXXZ (public: void __cdecl A::member_function(void))
?static_member@A@@2HA (public: static int A::static_member)
> dumpbin /exports mylib.dll
(some output skipped)
1 0 0001AAC8 ?global@@3HA
2 1 00001000 ?global_function@@YAXXZ
3 2 00001010 ?member_function@A@@QEAAXXZ
4 3 0001AACC ?static_member@A@@2HA
```
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