Re: bug in dlopen(3) man page

[Mike Frysinger <vapier-aBrp7R+bbdUdnm+yROfE0A@public.gmane.org>]

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On Sat 08 Mar 2014 22:30:59 Thomas Klausner wrote:
> There is a bug in dlopen(3). The NOTES section claims:
> 
> "The symbols RTLD_DEFAULT and RTLD_NEXT are defined by <dlfcn.h> only
> when _GNU_SOURCE was defined before including it."
> 
> However, this is not correct.
> 
> From dlfcn.h on a "Gentoo Base System release 2.1":
> #ifdef __USE_GNU
> ...
> # define RTLD_NEXT      ((void *) -1l)
> ...
> # define RTLD_DEFAULT   ((void *) 0)
> ...
> 
> You can verify this by compiling the attached program. For me it gives:
> test.c: In function `main':
> test.c:8: error: `RTLD_NEXT' undeclared (first use in this function)
> test.c:8: error: (Each undeclared identifier is reported only once
> test.c:8: error: for each function it appears in.)
> 
> It works if I set "__USE_GNU_" instead.
> 
> Please also check the "Glibc extensions: dladdr() and dlvsym()"
> section, it also mentions _GNU_SOURCE.

the man page is correct.  you must define _GNU_SOURCE before including any 
headers.  you must never use the __USE_XXX defines directly.

see feature_test_macros(7) for details as the dlopen() man page references.
-mike

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