Bug#207806: libc6-dev: [ppc] source code compatibility broken 2.3.1->2.3.2

[Christophe Rhodes <csr21@cam.ac.uk>]

Package: libc6-dev
Version: 2.3.1-17
Severity: important

This isn't about the platform or version of libc6-dev generated by 
reportbug, sorry, but about 2.3.2 on ppc.

The definition of ucontext_t and mcontext_t changed for powerpc32 
systems between 2.3.1 and 2.3.2.  They did so in a source-code 
incompatible way, such that programs of the form

#include <stdlib.h>
#include <signal.h>
#include <sys/types.h>
#include <sys/ucontext.h>
#include <unistd.h>

void sigsegv_handler(int sig, siginfo_t *info, void *context) {
  printf("PC = %x", (((ucontext_t *) context)->uc_mcontext.regs)->nip);
}

int main() {
  struct sigaction sa;
  pid_t pid;
  sa.sa_sigaction = sigsegv_handler;
  sa.sa_flags = SA_SIGINFO | SA_RESTART;
  sigaction(SIGSEGV, $sa, NULL);

  pid = getpid();
  kill(pid, SIGSEGV);
}

no longer compile, let alone run, because the mcontext_t structure no 
longer has an element "regs".

Furthermore, the new definition does not agree with what the kernel 
passes to signal handlers.  If I were to adjust the source code to use 
the new uc_mcontext structure slot and definition, I would end up with 
garbage in my signal handler, because the kernel does not put any 
information where libc has placed uc_mcontext.  It _does_ put some in 
the "for backwards compatibility" area, so I can get at the information 
using the uc_regs and uc_oldsigmask slots, but I can't see how this 
change has helped anyone.

It may be worth mentioning Debian bug #157374, where much the same 
problem (on hppa and mips) was discussed and fixed.  The bottom line is 
that the C library and the kernel's definition of a ucontext and an 
mcontext must agree.

Cheers,

Christophe
-- System Information:
Debian Release: testing/unstable
Architecture: i386
Kernel: Linux mu 2.4.21-1-686 #2 Mon Jun 16 22:13:09 EST 2003 i686
Locale: LANG=C, LC_CTYPE=C

Versions of packages libc6-dev depends on:
ii  libc6                         2.3.1-17   GNU C Library: Shared libraries an

-- no debconf information