[Buildroot] [PATCH 1/1] libkrb5: fix build on riscv

[Thomas Petazzoni <thomas.petazzoni@bootlin.com>]

Hello,

On Sun, 11 Nov 2018 21:15:10 +0100, Fabrice Fontaine wrote:

> > You did a similar change in libmicrothttpd, for which the same fix was
> > already done for ARC. Any idea why libmicrohttpd needs this hack for
> > both ARC and RISC-V, while libkrb5 would need it only for RISC-V ?  
> I didn't try to build libkrb5 on ARC but I found that back in 2016,
> for libmicrohttpd, you were writing that "Fixing the compilers is
> definitely the right thing to do":
> https://patchwork.ozlabs.org/patch/643857.
> Perhaps since that time, the ARC toolchains have been fixed?

Indeed! It was fixed in the following gcc commit:

commit de4c7f60f2891193bf3f5da823b17fa0d7fd4830
Author: claziss <claziss@138bc75d-0d04-0410-961f-82ee72b054a4>
Date:   Tue Mar 28 08:56:44 2017 +0000

    [ARC] Define _REENTRANT when -pthread is passed.
    
    The compiler is supposed to have the builtin defined _REENTRANT defined
    when -pthread is passed, which wasn't done on the ARC architecture.
    
    When _REENTRANT is not passed, the C library will not use reentrant
    functions, and the latest version of ax_pthread.m4 from the
    autoconf-archive will no longer detect that thread support is
    available (see https://savannah.gnu.org/patch/?8186).
    
    gcc/
    2017-03-28  Claudiu Zissulescu  <claziss@synopsys.com>
                Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
    
            * config/arc/arc.h (CPP_SPEC): Add subtarget_cpp_spec.
            (EXTRA_SPECS): Define.
            (SUBTARGET_EXTRA_SPECS): Likewise.
            (SUBTARGET_CPP_SPEC): Likewise.
            * config/arc/elf.h (EXTRA_SPECS): Renamed to
            SUBTARGET_EXTRA_SPECS.
            * config/arc/linux.h (SUBTARGET_CPP_SPEC): Define.
    
    git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk at 246524 138bc75d-0d04-0410-961f-82ee72b054a4

diff --git a/gcc/config/arc/linux.h b/gcc/config/arc/linux.h
index 6e1a96efc23..83e5a1d61f2 100644
--- a/gcc/config/arc/linux.h
+++ b/gcc/config/arc/linux.h
@@ -78,3 +78,8 @@ along with GCC; see the file COPYING3.  If not see
 /* Linux toolchains use r25 as the thread pointer register.  */
 #undef TARGET_ARC_TP_REGNO_DEFAULT
 #define TARGET_ARC_TP_REGNO_DEFAULT 25
+
+#undef SUBTARGET_CPP_SPEC
+#define SUBTARGET_CPP_SPEC "\
+   %{pthread:-D_REENTRANT} \
+"

This commit is in gcc upstream since gcc 7.1.0. So I guess we could
drop the ARC-specific workaround on libmicrohttpd, since we don't
really support "old" gcc versions on ARC anyway.

Best regards,

Thomas
-- 
Thomas Petazzoni, CTO, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com