To: bug-pth@gnu.org

Subject: [PATCH] fix pth for makecontext-less glibc on Linux 3.x kernels

Cc: pth-users@gnu.org

Attempting to build pth-2.0.7 on arm-linux-gnueabi, running a 3.x

kernel, and with a glibc that doesn't yet have makecontext et al

(glibc-2.14.1 in my case) results in the following during configure:

Machine Context Implementation:

checking for ucontext.h... yes

checking for makecontext... no

checking for swapcontext... no

checking for getcontext... no

checking for setcontext... no

checking for usable SVR4/SUSv2 makecontext(2)/swapcontext(2)... no

checking for signal.h... (cached) yes

checking for sigsetjmp... no

checking for siglongjmp... yes

checking for setjmp... yes

checking for longjmp... yes

checking for _setjmp... yes

checking for _longjmp... yes

checking for sigaltstack... yes

checking for sigstack... yes

checking for signal-mask aware setjmp(3)/longjmp(3)... yes: sjljlx

checking for typedef stack_t... (cached) yes

checking for direction of stack growth... down

checking for makecontext... (cached) no

checking for stack setup via makecontext... N.A.

checking for sigaltstack... (cached) yes

checking for typedef stack_t... (cached) yes

checking for stack setup via sigaltstack... ok

checking for sigstack... (cached) yes

checking for stack setup via sigstack... guessed

decision on mctx implementation... sjlj/sjljlx/none

Note the "sjljlx", that's bogus since sjljlx is a fallback for

truly ancient systems; the correct choice is ssjlj.

Configure succeeds, but 'make' then results in:

./shtool scpp -o pth_p.h -t pth_p.h.in -Dcpp -Cintern -M '==#==' pth_compat.c pth_debug.c pth_syscall.c pth_errno.c pth_ring.c pth_mctx.c pth_uctx.c pth_clean.c pth_time.c pth_tcb.c pth_util.c pth_pqueue.c pth_event.c pth_sched.c pth_data.c pth_msg.c pth_cancel.c pth_sync.c pth_attr.c pth_lib.c pth_fork.c pth_high.c pth_ext.c pth_string.c pthread.c

./libtool --mode=compile --quiet gcc -c -I. -O2 -pipe pth_debug.c

./libtool --mode=compile --quiet gcc -c -I. -O2 -pipe pth_ring.c

./libtool --mode=compile --quiet gcc -c -I. -O2 -pipe pth_pqueue.c

./libtool --mode=compile --quiet gcc -c -I. -O2 -pipe pth_time.c

./libtool --mode=compile --quiet gcc -c -I. -O2 -pipe pth_errno.c

./libtool --mode=compile --quiet gcc -c -I. -O2 -pipe pth_mctx.c

pth_mctx.c: In function '__pth_mctx_set':

pth_mctx.c:480:2: error: #error "Unsupported Linux (g)libc version and/or platform"

make: *** [pth_mctx.lo] Error 1

This happens because there's a Linux kernel version check that

unfortunately only recognises 2.x versions, so it classifies a

3.x kernel as "braindead", which selects sjljlx and causes the

breakage.

The fix is to expand the kernel version regexp in aclocal.m4 to

also accept 3.x kernels; with that fix configure says:

checking for signal-mask aware setjmp(3)/longjmp(3)... yes: ssjlj

checking for typedef stack_t... (cached) yes

checking for direction of stack growth... down

checking for makecontext... (cached) no

checking for stack setup via makecontext... N.A.

checking for sigaltstack... (cached) yes

checking for typedef stack_t... (cached) yes

checking for stack setup via sigaltstack... ok

checking for sigstack... (cached) yes

checking for stack setup via sigstack... guessed

decision on mctx implementation... sjlj/ssjlj/sas

Both 'make' and 'make test' then succeed.

m68k-linux' glibc also lacks makecontext() et al, so it too is sensitive

to the kernel version check.  For m68k there is some specific support

in the sjljlx fallback code which appears to work, but with the fix

m68k too gets to use sjlj/ssjlj/sas (which works fine btw).

Signed-off-by: Mikael Pettersson <mikpe@it.uu.se>

---

--- pth-2.0.7/aclocal.m4.~1~	2006-06-08 19:54:01.000000000 +0200

+++ pth-2.0.7/aclocal.m4	2012-05-30 18:44:42.000000000 +0200

@@ -1074,7 +1074,7 @@ case $PLATFORM in

         braindead=no

         case "x`uname -r`" in

 changequote(, )dnl

-            x2.[23456789]* ) ;;

+            x2.[23456789]* | x3.[0-9]* ) ;;

 changequote([, ])

             * ) braindead=yes ;;

         esac

--- pth-2.0.7/configure.~1~	2006-06-08 20:14:48.000000000 +0200

+++ pth-2.0.7/configure	2012-05-30 18:45:03.000000000 +0200

@@ -22512,7 +22512,7 @@ case $PLATFORM in

     *-*-linux* )

         braindead=no

         case "x`uname -r`" in

-            x2.[23456789]* ) ;;

+            x2.[23456789]* | x3.[0-9]* ) ;;

             * ) braindead=yes ;;

         esac