[Bug build/19816] New: [PATCH] Fix stack protector detection.

["woutershep at gmail dot com" <sourceware-bugzilla at sourceware dot org>]

https://sourceware.org/bugzilla/show_bug.cgi?id=19816

            Bug ID: 19816
           Summary: [PATCH] Fix stack protector detection.
           Product: glibc
           Version: unspecified
            Status: NEW
          Severity: normal
          Priority: P2
         Component: build
          Assignee: unassigned at sourceware dot org
          Reporter: woutershep at gmail dot com
                CC: carlos at redhat dot com
  Target Milestone: ---

Created attachment 9092
  --> https://sourceware.org/bugzilla/attachment.cgi?id=9092&action=edit
0001-Fix-stack-protector-detection.patch

I use a cross compiling gcc 6 (host amd64 -> target i686) that defaults
to -fstack-protector-strong and it is failing the configure check:

checking whether i686-pc-linux-gnu-gcc implicitly enables -fstack-protector...
no

The native version does it correctly:

checking whether x86_64-pc-linux-gnu-gcc implicitly enables
-fstack-protector... yes

So i looked into it and i found the following chunk in gcc
(gcc/config/i386/i386.c):

/* For 32-bit code we can save PIC register setup by using
   __stack_chk_fail_local hidden function instead of calling
   __stack_chk_fail directly.  64-bit code doesn't need to setup any PIC
   register, so it is better to call __stack_chk_fail directly.  */

So we need to check for __stack_chk_fail_local too, otherwise it causes
errors during the building of glibc like:

elf/librtld.os: In function `lookup_doit':
elf/rtld.c:509: undefined reference to `__stack_chk_fail_local'

(Attached is a patch to fix it with the same info in it)

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