use of ifndef inhibit_libc to disable the contents linux-unwind.h for targets with MD_UNWIND_SUPPORT

[Stephen M. Kenton]

During the recent discussion about cross compilers I was told "bugs 
happen", so I went hunting.
I have been digging into why building a cross compiler dies in different 
ways for different targets.
As seen below, the Linux targets which use glibc define 
MD_UNWIND_SUPPORT and have
a customized linux-unwind.h file.  However, mips and i386 start and end 
those files with
#ifndef inhibit_libc .... #endif statements which disable the entire 
contents of the file if inhibit_libc is set.
Those are the only two such targets I can successfully build with 
inhibit_libc without the use of enable-sjlj-exceptions.
Is there some reason that every instance of linux-unwind.h should not 
start and end with those same
#ifndef inhibit_libc ... #endif  statements?  Or, alternatively, should 
setting of inhibit_libc force
a #undef MD_UNWIND_SUPPORT at some suitably central place rather than 
doing things the
way that mips and i386 currently handle it?

Steve Kenton

[adminrig@454analyze gcc-4.2.1-stock]$ grep -r MD_UNWIND_SUPPORT 
gcc/config/*
gcc/config/alpha/gnu.h:#undef MD_UNWIND_SUPPORT
gcc/config/alpha/linux.h:#define MD_UNWIND_SUPPORT 
"config/alpha/linux-unwind.h"
gcc/config/alpha/vms.h:#define MD_UNWIND_SUPPORT "config/alpha/vms-unwind.h"
gcc/config/i386/gnu.h:#undef MD_UNWIND_SUPPORT
gcc/config/i386/linux64.h:#define MD_UNWIND_SUPPORT 
"config/i386/linux-unwind.h"
gcc/config/i386/linux.h:#define MD_UNWIND_SUPPORT 
"config/i386/linux-unwind.h"
gcc/config/ia64/linux.h:#define MD_UNWIND_SUPPORT 
"config/ia64/linux-unwind.h"
gcc/config/ia64/unwind-ia64.c:#ifdef MD_UNWIND_SUPPORT
gcc/config/ia64/unwind-ia64.c:#include MD_UNWIND_SUPPORT
gcc/config/mips/linux.h:#define MD_UNWIND_SUPPORT 
"config/mips/linux-unwind.h"
gcc/config/pa/pa32-linux.h:#define MD_UNWIND_SUPPORT 
"config/pa/linux-unwind.h"
gcc/config/pa/pa-hpux.h:#define MD_UNWIND_SUPPORT "config/pa/hpux-unwind.h"
gcc/config/rs6000/linux64.h:#define MD_UNWIND_SUPPORT 
"config/rs6000/linux-unwind.h"
gcc/config/rs6000/linux.h:#define MD_UNWIND_SUPPORT 
"config/rs6000/linux-unwind.h"
gcc/config/rs6000/darwin.h:#define MD_UNWIND_SUPPORT 
"config/rs6000/darwin-unwind.h"
gcc/config/s390/tpf.h:#define MD_UNWIND_SUPPORT "config/s390/tpf-unwind.h"
gcc/config/s390/linux.h:#define MD_UNWIND_SUPPORT 
"config/s390/linux-unwind.h"
gcc/config/sh/linux.h:#define MD_UNWIND_SUPPORT "config/sh/linux-unwind.h"
gcc/config/sparc/linux64.h:#define MD_UNWIND_SUPPORT 
"config/sparc/linux-unwind.h"
gcc/config/sparc/linux.h:#define MD_UNWIND_SUPPORT 
"config/sparc/linux-unwind.h"

[adminrig@454analyze gcc-4.2.1-stock]$ find  gcc/config -name linux-unwind.h
gcc/config/sparc/linux-unwind.h
gcc/config/mips/linux-unwind.h
gcc/config/i386/linux-unwind.h
gcc/config/pa/linux-unwind.h
gcc/config/ia64/linux-unwind.h
gcc/config/sh/linux-unwind.h
gcc/config/s390/linux-unwind.h
gcc/config/rs6000/linux-unwind.h
gcc/config/alpha/linux-unwind.h

[adminrig@454analyze gcc-4.2.1-stock]$ grep inhibit_libc `find  
gcc/config -name linux-unwind.h`
gcc/config/mips/linux-unwind.h:#ifndef inhibit_libc
gcc/config/i386/linux-unwind.h:   Don't use this at all if inhibit_libc 
is used.  */
gcc/config/i386/linux-unwind.h:#ifndef inhibit_libc
gcc/config/i386/linux-unwind.h:#endif /* ifdef inhibit_libc  */
[adminrig@454analyze gcc-4.2.1-stock]$