[Buildroot] Problems with uClicbc and libc.so.6

[Angelo Compagnucci]

Hi Thomas,

I really would like to understand better this issue, if you are so
kind to help me!

> If something depends on libc.so.6, it means it was built against glibc,
> and cannot work against uClibc. So either it's something built from
> source, and you should rebuilt it with the uClibc toolchain. Or it's
> something available as a pre-built binary for which you don't have the
> source, in which case you have no other choice than using glibc.

I just rebuilt everything from scratch using the latest buildroot git
and the problem persists.
The package I'm using is more or less this one:

http://patchwork.ozlabs.org/patch/392957/, I've only added a small
patch to make compile cleanly with uClibc.

diff -purN mono-native-3.8.0.orig/libgc/include/gc.h
mono-native-3.8.0/libgc/include/gc.h
--- mono-native-3.8.0.orig/libgc/include/gc.h 2014-10-07
15:00:21.259466731 +0200
+++ mono-native-3.8.0/libgc/include/gc.h 2014-10-07 15:05:25.560975681 +0200
@@ -500,7 +500,7 @@ GC_API GC_PTR GC_malloc_atomic_ignore_of
 #ifdef __linux__
 # include <features.h>
 # if (__GLIBC__ == 2 && __GLIBC_MINOR__ >= 1 || __GLIBC__ > 2) \
-     && !defined(__ia64__)
+     && !defined(__ia64__) && !defined(__UCLIBC__)
 #   ifndef GC_HAVE_BUILTIN_BACKTRACE
 #     define GC_HAVE_BUILTIN_BACKTRACE
 #   endif

This package is based on my previous work that I used regularly on
older buildroot versions. The only thing that changed is the bump to
mono version 3.8.0.

> I am a bit surprised that it works. It is in any case completely wrong,
> and there is absolutely no guarantee that uClibc and glibc are ABI
> compatible.

Based on my limited knowledge of Buildroot internals, it should work
because the only toolchain I selected is the one built by buildroot
with uClibc 0.9.33.x. Honestly I think that something in between mono
cross compilation links erroneously to libc instead to uClibc so the
error is explained.

I can disable mono when toolchain is uClibc based, but I really want
to narrow down and resolve the problem.

Thank you for your time!

Angelo

>
> Best regards,
>
> Thomas
> --
> Thomas Petazzoni, CTO, Free Electrons
> Embedded Linux, Kernel and Android engineering
> http://free-electrons.com



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