Bochs

History

Bryce Denney 5b555711f2 - minor changes to make this work in win32: define LT_SCOPE to be extern before including <ltdl.h>. Otherwise it tries to export some symbols from main.cc, which then conflict with the real ltdl when it gets linked. - on win32 I am not using libtool to build the libraries, so I need to use a different format string for module names. On win32 use "%s.dll". - call lt_dlopenext() instead of lt_dlopen() because it searches for filenames using various extensions including the libtool extension .la and also the system's native library name (.so or whatever).		2002-10-16 01:28:41 +00:00
..
main.cc	- minor changes to make this work in win32: define LT_SCOPE to be extern	2002-10-16 01:28:41 +00:00
main.h	- move the extern "C" declaration of module_init into main.h so that it	2002-10-13 02:22:37 +00:00
Makefile.in	- put INCLTDL and LIBLTDL substitution variables into the Makefile	2002-10-12 12:29:35 +00:00
module1.cc	- move the extern "C" declaration of module_init into main.h so that it	2002-10-13 02:22:37 +00:00
module2.cc	- add test6, which actually tries to open a shared lib with lt_dlopen.	2002-10-12 05:52:15 +00:00
README	- mention backtrace of an ltdl error msg	2002-10-14 21:02:53 +00:00

README

test6-execsymbols2

Try again to allow the module to reference symbols in the executable. 
But this time, eliminate direct symbol references from the executable 
to the module, so that the executable can be linked first.  I believe
this will work ok for win32 and it's closer to how plugins need to work.

What I think I learned from test5:
> DLLs don't allow any symbols to be undefined at link time.  So you have to
> choose the order of how to build things so that each link is complete.
> For a DLL that's used as a shared library, it must be built and linked on
> its own (without the program), with symbols exported.  This link must be
> complete, so it can't depend on pieces from the program.  Then, the 
> program can be linked with the DLL, with the program reading symbols from
> the DLL.  It can't go both ways.
> 
> For a plugin environment, we want the plugin to be able to call functions
> in the main code, without putting every single thing as a function pointer.
> So the main executable should be built first, with appropriate symbols 
> exported, and then the plugin can import those symbols.  The main 
> executable will find symbols in the DLL using lt_dlopen() and lt_dlsym(),
> which probably maps to LoadLibrary() and GetProcAddress().


module1.lo: In function `module_init(void)':
/home/bryce/bochs-testing/plugin-test/test6-execsymbols2/module1.cc:7: undefined reference to `import stub for register_module(char const *)'

---------------------
ltdl error
Program received signal SIGSEGV, Segmentation fault.
tryall_dlopen_module (handle=0x78f928, prefix=0x0, dirname=0x0, 
dlname=0x100d2118 "cygmodule1-0.dll") at ltdl.c:1958
1958      if (dirname[dirname_len -1] == '/')
Current language:  auto; currently c
(gdb) where
#0  tryall_dlopen_module (handle=0x78f928, prefix=0x0, dirname=0x0, 
    dlname=0x100d2118 "cygmodule1-0.dll") at ltdl.c:1958
#1  0x1000249b in find_module (handle=0x78f928, dir=0x0, libdir=0x100d2190
	"/home/bryce/bochs-testing/plugin-test/test6-ltdlopen/lib",
	dlname=0x100d2118 "cygmodule1-0.dll", old_name=0x100d2130 "libmodule1.a",
	installed=0) at ltdl.c:2024
#2  0x100035f8 in try_dlopen (phandle=0x78f958, 
    filename=0x78f98c "libmodule1.la") at ltdl.c:2798
#3  0x100038a5 in lt_dlopen (filename=0x78f98c "libmodule1.la") at ltdl.c:2893
#4  0x10001143 in load_module (fmt=0x100011fc "lib%s.la", 
    name=0x100011f4 "module1") at main.cc:19
#5  0x100012bb in main (argc=1, argv=0x100d0e60) at main.cc:46