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Message-ID: <39E259A7.CBAD325F@ece.gatech.edu>
Date: Mon, 09 Oct 2000 19:49:59 -0400
From: Charles Wilson <cwilson AT ece DOT gatech DOT edu>
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To: cygwin AT sourceware DOT cygnus DOT com
Subject: Re: AW: Linking Dynamic Libraries
References: <004501c031f0$10478ad0$0d33028b AT zapperlot DOT materna DOT de> <39E1CC08 DOT F475851F AT ece DOT gatech DOT edu> <39E2468B DOT BFDD3AB7 AT ihug DOT co DOT nz>
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You still need to worry about things like __declspec(dllexport) and
__declspec(dllimport).  Here's a patch for your files.  

(Yes, you are correct; the option is '--export-all-symbols' not
'--export-all')

As far as documentation, there's the mailing list, and 'ld --help' and
Mumit's (really out-of-date) dll-helpers packaqe at
http://www.xraylith.wisc.edu/~khan/software/gnu-win32/dllhelpers.html. 
Would you like to update that package for the current capabilities of
ld/gcc ?  Mumit's tutorial is heavily 'dlltool' based, rather than 'gcc
-shared' or 'ld' based.

NOTE 1: I had to remove "-Wl,--export-all-symbols" from the options;
with export-all I got a stack dump even with my other changes. I'm not
sure why.

NOTE 2: I used the extension '.dll.a' for the import library; cygwin's
linker will search for 'libfoo.dll.a' in preference to 'libfoo.a';
libfoo.a is assumed to be a static library (although the linker will use
libfoo.a if .dll.a is not found)

--Chuck


diff -u demo-orig/Makefile demo/Makefile
--- demo-orig/Makefile  Mon Oct  9 19:34:15 2000
+++ demo/Makefile       Mon Oct  9 19:45:10 2000
@@ -3,7 +3,7 @@
 EXENAME = demo
 EXEOBJ = demo.o
 CPLUS = g++ -W -Wall -Werror
-LINKDLL = g++ -shared -Wl,--export-all -Wl,--enable-auto-image-base
+LINKDLL = g++ -shared -Wl,--enable-auto-image-base
 LINKEXE = g++ -L.
 
 .DELETE_ON_ERROR:
@@ -13,13 +13,16 @@
 all: $(DLLNAME).dll $(EXENAME)
 
 clean:
-       rm -f $(DLLOBJ) $(DLLNAME).dll lib$(DLLNAME).a $(EXEOBJ)
$(EXENAME).exe
+       rm -f $(DLLOBJ) $(DLLNAME).dll lib$(DLLNAME).dll.a $(EXEOBJ)
$(EXENAME).exe
 
 %.o: %.cpp
        $(CPLUS) -c $< -o $@
 
+$(DLLOBJ): $(DLLOBJ:.o=.cpp)
+       $(CPLUS) -DBUILD_DLL -c $< -o $@
+
 $(DLLNAME).dll: $(DLLOBJ)
-       $(LINKDLL) $(DLLOBJ) -o $(DLLNAME).dll
-Wl,--out-implib=lib$(DLLNAME).a
+       $(LINKDLL) $(DLLOBJ) -o $(DLLNAME).dll
-Wl,--out-implib=lib$(DLLNAME).dll.a
 
 $(EXENAME): $(EXEOBJ) $(DLLNAME).dll
        $(LINKEXE) $(EXEOBJ) -l$(DLLNAME) -o $(EXENAME)
diff -u demo-orig/foo.hpp demo/foo.hpp
--- demo-orig/foo.hpp   Mon Oct  9 19:35:58 2000
+++ demo/foo.hpp        Mon Oct  9 19:35:50 2000
@@ -3,7 +3,12 @@
 
 #include <string>
 
-extern std::string global_mangle(const std::string& source);
-
+#ifdef BUILD_DLL
+#define FOO_EXPORT __declspec(dllexport)
+#else
+#define FOO_EXPORT __declspec(dllimport)
 #endif
 
+extern FOO_EXPORT std::string global_mangle(const std::string& source);
+
+#endif

Ross Smith wrote:
> 
> "Charles S. Wilson" wrote:
> >
> > There's an easier way -- one command!  'gcc -shared' will create a dll
> > for you.  Just do:
> >
> > $(BASE)=foo
> >
> >   gcc -shared -o cyg$(BASE).dll -Wl,--out-implib=lib$(BASE).dll.a \
> >     -Wl,--export-all -Wl,--enable-auto-image-base \
> >     -Wl,--output-def=cyg$(BASE).def $(OBJS)
> 
> I can't get this to work. Whenever I link with the import lib produced
> this way, the resulting program crashes with a STATUS_ACCESS_VIOLATION.
> (See attached code.) I don't even need to call any of the DLL functions
> to trigger it -- just linking with -lfoo makes it unworkable. What am I
> doing wrong?
> 
> And where is all this stuff documented anyway? The ld docs mention
> --export-all-symbols (not --export-all), but not any of the others.
> 
> -------------------- cut here --------------------
> 
> // demo.cpp
> 
> #include "foo.hpp"
> #include <iostream>
> #include <string>
> 
> int main() {
>   std::string thing("thing");
>   std::cout << thing << std::endl;
> //  std::cout << global_mangle(thing) << std::endl;
>   return 0;
> }
> 
> -------------------- cut here --------------------
> 
> // foo.hpp
> 
> #ifndef FOO_HEADER
> #define FOO_HEADER
> 
> #include <string>
> 
> extern std::string global_mangle(const std::string& source);
> 
> #endif
> 
> -------------------- cut here --------------------
> 
> // foo.cpp
> 
> #include "foo.hpp"
> 
> std::string global_mangle(const std::string& source) {
>   return source + "_global";
> }
> 
> -------------------- cut here --------------------
> 
> // Makefile
> 
> DLLNAME = foo
> DLLOBJ = foo.o
> EXENAME = demo
> EXEOBJ = demo.o
> CPLUS = g++ -W -Wall -Werror
> LINKDLL = g++ -shared -Wl,--export-all -Wl,--enable-auto-image-base
> LINKEXE = g++ -L.
> 
> .DELETE_ON_ERROR:
> 
> .PHONY: all clean
> 
> all: $(DLLNAME).dll $(EXENAME)
> 
> clean:
>     rm -f $(DLLOBJ) $(DLLNAME).dll lib$(DLLNAME).a $(EXEOBJ)
> $(EXENAME).exe
> 
> %.o: %.cpp
>     $(CPLUS) -c $< -o $@
> 
> $(DLLNAME).dll: $(DLLOBJ)
>     $(LINKDLL) $(DLLOBJ) -o $(DLLNAME).dll
> -Wl,--out-implib=lib$(DLLNAME).a
> 
> $(EXENAME): $(EXEOBJ) $(DLLNAME).dll
>     $(LINKEXE) $(EXEOBJ) -l$(DLLNAME) -o $(EXENAME)
> 
> demo.o: demo.cpp foo.hpp
> foo.o: foo.cpp foo.hpp
> 
> -------------------- cut here --------------------
> 
> --
> Ross Smith <ross DOT s AT ihug DOT co DOT nz> The Internet Group, Auckland, New Zealand
> ========================================================================
> "C++ is to programming as sex is to reproduction. Better ways might
> technically exist but they're not nearly as much fun." -- Nikolai Irgens
> 
> --
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> Send a message to cygwin-unsubscribe AT sourceware DOT cygnus DOT com

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