'RTLD_NEXT' undeclared

Question

I'm trying to compile a C program but I get the error 'RTLD_NEXT' undeclared. I think this is supposed to be defined in dlfcn.h which the c program includes, but when I looked inside dlfcn.h there is no RTLD_NEXT.

How do I fix this?

You had better tell us exactly what Linux distro and gcc version if you are defining _GNU_SOURCE and not succeeding. — bmargulies, Nov 22 '09 at 02:21
@bmargulies: he's using cygwin (see http://stackoverflow.com/questions/1777523/how-to-make-this-c-program-compile/1777566#1777566 ), which does not support `RTLD_NEXT` (see eg http://lists.zerezo.com/cygwin/msg38882.html ) — Christoph, Nov 22 '09 at 02:41

bmargulies · Answer 1 · 2009-11-22T02:18:45.237

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The issue here is that RTLD_NEXT is not defined by the posix standard . So the GNU people don't enable it unless you #define _GNU_SOURCE or -D_GNU_SOURCE.

Other relevant pieces of POSIX are dlfcn.h and dlsym.h. Interestingly, the later mentions RTLD_NEXT. Apparently, the GNU people are a bit confused about what is an extension and what is not.

edited Nov 22 '09 at 02:18

answered Nov 22 '09 at 01:46

bmargulies

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better link to http://www.opengroup.org/onlinepubs/009695399/basedefs/dlfcn.h.html and http://www.opengroup.org/onlinepubs/009695399/functions/dlsym.html#tag_03_112_07 – Christoph Nov 22 '09 at 01:56

score 10 · Answer 2 · edited Dec 12 '11 at 08:58

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According to man dlsym it is #define _GNU_SOURCE (just one leading underscore) before the dlfcn.h is included. (RHEL6.1).

edited Dec 12 '11 at 08:58

eeerahul

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answered Dec 12 '11 at 08:34

Martin

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score 5 · Answer 3 · edited Jun 21 '11 at 17:32

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Try #define __GNU_SOURCE as first line in your sources.

edited Jun 21 '11 at 17:32

bmargulies

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answered Nov 22 '09 at 01:37

user175104

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It's actually `__USE_GNU`, just noting since this is the top Google result for "RTLD_NEXT" now. – correnos Apr 02 '12 at 13:33
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It is just *one* leading underscore: `#define _GNU_SOURCE`. – Jonathon Reinhart Sep 10 '14 at 02:08

abhishek bv · Answer 4 · 2017-12-15T20:05:36.067

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There must be one underscore. #define _GNU_SOURCE Further, this must be your first preprocessor directive.For example:

#define _GNU_SOURCE  
#include <stdio.h>

edited Dec 15 '17 at 20:05

answered Dec 14 '17 at 05:02

abhishek bv

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'RTLD_NEXT' undeclared

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