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fa046b6a92
This restores the Linux behavior to what it was in PG 7.0 and 7.1, and causes other platforms to agree. (Other well-tested platforms like HPUX were doing it this way already.) Per pghackers discussion over the past month or so.
168 lines
5.6 KiB
Plaintext
168 lines
5.6 KiB
Plaintext
Copyright (c) 1992,1993,1995, Jens-Uwe Mager, Helios Software GmbH
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Not derived from licensed software.
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Permission is granted to freely use, copy, modify, and redistribute
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this software, provided that no attempt is made to gain profit from it,
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the author is not construed to be liable for any results of using the
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software, alterations are clearly marked as such, and this notice is
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not modified.
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libdl.a
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-------
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This is an emulation library to emulate the SunOS/System V.4 functions
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to access the runtime linker. The functions are emulated by using the
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AIX load() function and by reading the .loader section of the loaded
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module to find the exports. The to be loaded module should be linked as
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follows (if using AIX 3):
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cc -o module.so -bM:SRE -bE:module.exp -e _nostart $(OBJS)
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For AIX 4:
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cc -o module.so -bM:SRE -bE:module.exp -bnoentry $(OBJS)
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The module export file contains the symbols to be exported. Because
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this library uses the loader section, the final module.so file can be
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stripped. C++ users should build their shared objects using the script
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makeC++SharedLib (part of the IBM C++ compiler), this will make sure
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that constructors and destructors for static and global objects will be
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called upon loading and unloading the module.
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Usage
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-----
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void *dlopen(const char *path, int mode);
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This routine loads the module pointed to by path and reads its export
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table. If the path does not contain a '/' character, dlopen will search
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for the module using the LIBPATH environment variable. It returns an
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opaque handle to the module or NULL on error. The mode parameter can be
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either RTLD_LAZY (for lazy function binding) or RTLD_NOW for immediate
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function binding. The AIX implementation currently behaves as RTLD_NOW
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even if RTLD_LAZY is specified. The flag RTLD_GLOBAL might be or'ed into the
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mode parameter to allow loaded modules to bind to global variables or
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functions in other loaded modules loaded by dlopen(). If RTLD_GLOBAL is
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not specified, only globals from the main part of the executable or
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shared libraries are used to look for undefined symbols in loaded
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modules.
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void *dlsym(void *handle, const char *symbol);
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This routine searches for the symbol in the module referred to by
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handle and returns its address. If the symbol could not be found, the
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function returns NULL. The return value must be casted to a proper
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function pointer before it can be used. SunOS/System V.4 allow handle
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to be a NULL pointer to refer to the module the call is made from, this
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is not implemented.
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int dlclose(void *handle);
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This routine unloads the module referred to by the handle and disposes
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of any local storage. this function returns -1 on failure.
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char *dlerror(void);
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This routine can be used to retrieve a text message describing the most
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recent error that occured on on of the above routines. This function
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returns NULL if there is not error information.
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Initialization and termination handlers
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---------------------------------------
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The emulation provides for an initialization and a termination
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handler. The dlfcn.h file contains a structure declaration named
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dl_info with following members:
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void (*init)(void);
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void (*fini)(void);
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The init function is called upon first referencing the library. The
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fini function is called at dlclose() time or when the process exits.
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The module should declare a variable named dl_info that contains this
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structure which must be exported. These functions correspond to the
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documented _init() and _fini() functions of SunOS 4.x, but these are
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appearently not implemented in SunOS. When using SunOS 5.0, these
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correspond to #pragma init and #pragma fini respectively. At the same
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time any static or global C++ object's constructors or destructors will
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be called.
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Jens-Uwe Mager
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HELIOS Software GmbH
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Lavesstr. 80
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30159 Hannover
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Germany
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Phone: +49 511 36482-0
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FAX: +49 511 36482-69
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AppleLink: helios.de Attn: Jens-Uwe Mager
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Internet: jum@helios.de
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Revison History
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---------------
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SCCS/s.dlfcn.h:
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D 1.4 95/04/25 09:36:52 jum 4 3 00018/00004/00028
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MRs:
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COMMENTS:
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added RTLD_GLOBAL, include and C++ guards
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D 1.3 92/12/27 20:58:32 jum 3 2 00001/00001/00031
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MRs:
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COMMENTS:
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we always have prototypes on RS/6000
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D 1.2 92/08/16 17:45:11 jum 2 1 00009/00000/00023
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MRs:
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COMMENTS:
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added dl_info structure to implement initialize and terminate functions
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D 1.1 92/08/02 18:08:45 jum 1 0 00023/00000/00000
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MRs:
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COMMENTS:
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Erstellungsdatum und -uhrzeit 92/08/02 18:08:45 von jum
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SCCS/s.dlfcn.c:
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D 1.7 95/08/14 19:08:38 jum 8 6 00026/00004/00502
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MRs:
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COMMENTS:
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Integrated the fixes from Kirk Benell (kirk@rsinc.com) to allow loading of
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shared objects generated under AIX 4. Fixed bug that symbols with exactly
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8 characters would use garbage characters from the following symbol value.
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D 1.6 95/04/25 09:38:03 jum 6 5 00046/00006/00460
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MRs:
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COMMENTS:
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added handling of C++ static constructors and destructors, added RTLD_GLOBAL to bind against other loaded modules
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D 1.5 93/02/14 20:14:17 jum 5 4 00002/00000/00464
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MRs:
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COMMENTS:
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added path to dlopen error message to make clear where there error occured.
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D 1.4 93/01/03 19:13:56 jum 4 3 00061/00005/00403
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MRs:
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COMMENTS:
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to allow calling symbols in the main module call load with L_NOAUTODEFER and
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do a loadbind later with the main module.
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D 1.3 92/12/27 20:59:55 jum 3 2 00066/00008/00342
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MRs:
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COMMENTS:
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added search by L_GETINFO if module got loaded by LIBPATH
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D 1.2 92/08/16 17:45:43 jum 2 1 00074/00006/00276
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MRs:
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COMMENTS:
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implemented initialize and terminate functions, added reference counting to avoid multiple loads of the same library
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D 1.1 92/08/02 18:08:45 jum 1 0 00282/00000/00000
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MRs:
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COMMENTS:
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Erstellungsdatum und -uhrzeit 92/08/02 18:08:45 von jum
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