FPC can't link DLL directly
lazarus / 62-General

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jiaxing2 · 2020-05-12 10:23

I tried to link sgl64.dll directly. sgl64.dll is compiled by Pelles C.

http://perso.numericable.fr/hserindat/sgl/

Even after I contact and get sgl64.dll compiled by MinGW, it still
can't link.

It always ended up with Illegal COFF format error.

I found I have to create an .a import library for it in other to link
the DLL.

I think this is a bug. As on Linux, I can link .so library with no
problem.

FPC version is 3.0.4 shipped with Lazarus 64 bit on Windows 7.

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marcov · 2020-05-12 10:33

- no way to reproduce the problem. You show no code. Most notably the
external declarations. (*)
- not really excluding that you are accidentally using the 32-bit
compiler.

(*) On windows, external declarations should have a NAME part and
contain the name of the dll.  On Linux just "external"  is enough.

The reason for that Linux dynamic linker searches all libraries for a
symbol, Windows has something called linker namespaces, in that it
only searches for a symbol in a given library (thus allowing multiple
occurrences of the same name in differing libraries)

Probably if you fix the declaration, the importlibrary parts will be
auto-generated. FPC hasn't required importlibraries since before 2000.


(p.s. I accidentally appended your post with the above two lines.
Moderator only mistake. I fixed it)

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jiaxing2 · 2020-05-12 17:30

Quote from: marcov on May 12, 2020, 12:33:40 pm(*) On windows,
external declarations should have a NAME part and contain the name of
the dll.  On Linux just "external"  is enough.

So it's the problem. I only h2pas -d option. Now I have to use -D -l
"libname" instead.