2020-09-20 Paul Eggert <eggert@cs.ucla.edu>
+ c-stack: output diagnostic in single 'write'
+ * lib/c-stack.c (die): In the typical case, use just one 'write'
+ syscall to output the diagnostic, as this lessens interleaving.
+ (die, c_stack_action): Assume C99.
+ * modules/c-stack (Depends-on): Add c99, mempcpy.
+
c-stack: improve checking if !libsigsegv
If SIGINFO_WORKS, do not treat a null pointer dereference as if it
were a stack overflow. Use uintptr_t and INT_ADD_WRAPV to avoid
static _GL_ASYNC_SAFE _Noreturn void
die (int signo)
{
- char const *message;
# if !SIGINFO_WORKS && !USE_LIBSIGSEGV
/* We can't easily determine whether it is a stack overflow; so
assume that the rest of our program is perfect (!) and that
signo = 0;
# endif
segv_action (signo);
- message = signo ? program_error_message : stack_overflow_message;
- ignore_value (write (STDERR_FILENO, progname, strlen (progname)));
- ignore_value (write (STDERR_FILENO, ": ", 2));
- ignore_value (write (STDERR_FILENO, message, strlen (message)));
- ignore_value (write (STDERR_FILENO, "\n", 1));
+ char const *message = signo ? program_error_message : stack_overflow_message;
+
+ /* If the message is short, write it all at once to avoid
+ interleaving with other messages. Avoid writev as it is not
+ documented to be async-signal-safe. */
+ size_t prognamelen = strlen (progname);
+ size_t messagelen = strlen (message);
+ static char const separator[] = {':', ' '};
+ char buf[SIGSTKSZ / 16 + sizeof separator];
+ ptrdiff_t buflen;
+ if (prognamelen + messagelen < sizeof buf - sizeof separator)
+ {
+ char *p = mempcpy (buf, progname, prognamelen);
+ p = mempcpy (p, separator, sizeof separator);
+ p = mempcpy (p, message, messagelen);
+ *p++ = '\n';
+ buflen = p - buf;
+ }
+ else
+ {
+ ignore_value (write (STDERR_FILENO, progname, prognamelen));
+ ignore_value (write (STDERR_FILENO, separator, sizeof separator));
+ ignore_value (write (STDERR_FILENO, message, messagelen));
+ buf[0] = '\n';
+ buflen = 1;
+ }
+ ignore_value (write (STDERR_FILENO, buf, buflen));
+
if (! signo)
_exit (exit_failure);
raise (signo);
int
c_stack_action (_GL_ASYNC_SAFE void (*action) (int))
{
- int r;
stack_t st;
- struct sigaction act;
st.ss_flags = 0;
# if SIGALTSTACK_SS_REVERSED
/* Irix mistakenly treats ss_sp as the upper bound, rather than
st.ss_sp = alternate_signal_stack.buffer;
st.ss_size = sizeof alternate_signal_stack.buffer;
# endif
- r = sigaltstack (&st, NULL);
+ int r = sigaltstack (&st, NULL);
if (r != 0)
return r;
page_size = sysconf (_SC_PAGESIZE);
# endif
+ struct sigaction act;
sigemptyset (&act.sa_mask);
# if SIGINFO_WORKS