Subject: Documentation suggestion

From: Reuben Thomas <[email-masked]>
Date: Thu, 23 Apr 2020 13:15:30 +0100

libtool.texi contains the following:

"It was reported that GNU/Linux's glibc 2.0's 'dlopen' with 'RTLD_LAZY'
(that libltdl uses by default) is not thread-safe, but this problem is
supposed to be fixed in glibc 2.1.  On the other hand, 'RTLD_NOW' was
reported to introduce problems in multi-threaded applications on FreeBSD."

I suggest removing this material: glibc 2.1 was released over 20 years ago.
I have looked through both the glibc changelogs and git history to try to
ascertain whether in fact this bug was mentioned as being fixed, but I can
find nothing relevant. The same applies to the FreeBSD case.

Evidence on the positive side is that dlopen(3) states explicitly that the
function is thread safe, and POSIX defines it as such. Therefore it might
be reasonable to state that modern dlopen implementations should be threads
safe. Or it might not. (Does someone know more about this?) In the latter
case, the rest of the paragraph could be left as-is, which is to say,
reasonably conservative.

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