RE: PATCH: allow PE executables to have an export table

[fabrizio dot ge at tiscali dot it]

>-- Messaggio Originale --
>From: "Ralf Habacker" <Ralf.Habacker@freenet.de>
>To: "Fabrizio Gennari" <fabrizio.ge@tiscalinet.it>,
>	<binutils@sources.redhat.com>
>Subject: RE: PATCH: allow PE executables to have an export table
>Date: Wed, 18 Dec 2002 02:01:51 +0100
>
>
>> Current version of ld has a limitation: PE executables generated by ld
never
>> have an export table, although PE shared libraries (DLLs) have one. In
fact,
>> an export table in an executable file is perfectly legitimate
>
>Hi Fabrizio,
>
>allow me one question: for which cases should this be good ?
>The advantage is that an application(1) could be linked to another
>application(2) or dll(3), but makes this sense ?
>I assume the windows runtime linker could not load the application (1),
because
>it does not contain the structure and the startup code, dll's usually have.
>

The idea is to have a Windows equivalent of --export-dynamic used with ELF
files: if an application dlopen()s a DLL, the DLL is able to call the
calling executable's exported functions. This way, a developer is able to
write a portable application which uses --export-dynamic on Unix-like systems
and an export table on Windows.

Following Danny Smith's advice, I searched the mingw-users archive and found
a very interesting post:

>From: Tor Lillqvist <tml@ik...>
> Exporting symbols from a .exe
>2002-01-04 11:39
> Andrew Begel writes:
>  > __declspec(dllexport) int main(int argc, char **argv) {
>
>  > And I want to export main from the .exe. So I compile this using:
>
> (Export main? That sounds a bit odd to me. So you want to load a DLL
> in the program, and then have the DLL call main recursively? But I
> digress.)
>
>  > gcc -o foobar.exe foobar.c
>
>  > and the resulting executable doesn't export main (as reported dumpbin)!
>
> You have to first compile main.c with
> 	gcc -c main.c
> then run
> 	dlltool --output-exp main.exp main.o
> then link it
> 	gcc -o main.exe main.o main.exp
>
> For some reason ld doesn't believe the __declspec(dllexport)
> directives when building .exe files, but you have to create an .exp
> file and link with that.

So, it seems that current version of ld creates export tables (I didn't
know!), but only if passed a .exp file: .def files and _declspec(dllexport)
directives do not work. The patch just fills this gap.

Regards
Fabrizio



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