add sockets wrappers

[gnulib.git] / m4 / c-stack.m4

diff --git a/m4/c-stack.m4 b/m4/c-stack.m4
index b1f93ed..4f0300b 100644 (file)
--- a/m4/c-stack.m4
+++ b/m4/c-stack.m4
@@ -7,7 +7,7 @@
 
 # Written by Paul Eggert.
 
-# serial 3
+# serial 6
 
 AC_DEFUN([AC_SYS_XSI_STACK_OVERFLOW_HEURISTIC],
   [# for STACK_DIRECTION
@@ -16,6 +16,89 @@ AC_DEFUN([AC_SYS_XSI_STACK_OVERFLOW_HEURISTIC],
    AC_CHECK_HEADERS_ONCE([ucontext.h])
 
    AC_CACHE_CHECK([for working C stack overflow detection],
+     [ac_cv_sys_stack_overflow_works],
+     [AC_TRY_RUN(
+       [
+        #include <unistd.h>
+        #include <signal.h>
+        #if HAVE_SETRLIMIT
+        # include <sys/types.h>
+        # include <sys/time.h>
+        # include <sys/resource.h>
+        #endif
+         #ifndef SIGSTKSZ
+         # define SIGSTKSZ 16384
+         #endif
+
+        static union
+        {
+          char buffer[SIGSTKSZ];
+          long double ld;
+          long u;
+          void *p;
+        } alternate_signal_stack;
+
+        static void
+        segv_handler (int signo)
+        {
+          _exit (0);
+        }
+
+        static int
+        c_stack_action ()
+        {
+          stack_t st;
+          struct sigaction act;
+          int r;
+
+          st.ss_flags = 0;
+          st.ss_sp = alternate_signal_stack.buffer;
+          st.ss_size = sizeof alternate_signal_stack.buffer;
+          r = sigaltstack (&st, 0);
+          if (r != 0)
+            return r;
+
+          sigemptyset (&act.sa_mask);
+          act.sa_flags = SA_NODEFER | SA_ONSTACK | SA_RESETHAND;
+          act.sa_handler = segv_handler;
+          return sigaction (SIGSEGV, &act, 0);
+        }
+
+        static int
+        recurse (char *p)
+        {
+          char array[500];
+          array[0] = 1;
+          return *p + recurse (array);
+        }
+
+        int
+        main ()
+        {
+          #if HAVE_SETRLIMIT && defined RLIMIT_STACK
+          /* Before starting the endless recursion, try to be friendly
+             to the user's machine.  On some Linux 2.2.x systems, there
+             is no stack limit for user processes at all.  We don't want
+             to kill such systems.  */
+          struct rlimit rl;
+          rl.rlim_cur = rl.rlim_max = 0x100000; /* 1 MB */
+          setrlimit (RLIMIT_STACK, &rl);
+          #endif
+
+          return c_stack_action () || recurse ("\1");
+        }
+       ],
+       [ac_cv_sys_stack_overflow_works=yes],
+       [ac_cv_sys_stack_overflow_works=no],
+       [ac_cv_sys_stack_overflow_works=cross-compiling])])
+
+  if test $ac_cv_sys_stack_overflow_works = yes; then
+   AC_DEFINE([HAVE_STACK_OVERFLOW_HANDLING], [1],
+     [Define to 1 if extending the stack slightly past the limit causes
+      a SIGSEGV which can be handled on an alternate stack established
+      with sigaltstack.])
+
+   AC_CACHE_CHECK([for precise C stack overflow detection],
      ac_cv_sys_xsi_stack_overflow_heuristic,
      [AC_TRY_RUN(
        [
@@ -29,6 +112,9 @@ AC_DEFUN([AC_SYS_XSI_STACK_OVERFLOW_HEURISTIC],
         # include <sys/time.h>
         # include <sys/resource.h>
         #endif
+         #ifndef SIGSTKSZ
+         # define SIGSTKSZ 16384
+         #endif
 
         static union
         {
@@ -114,8 +200,7 @@ AC_DEFUN([AC_SYS_XSI_STACK_OVERFLOW_HEURISTIC],
           setrlimit (RLIMIT_STACK, &rl);
           #endif
 
-          c_stack_action ();
-          return recurse ("\1");
+          return c_stack_action () || recurse ("\1");
         }
        ],
        [ac_cv_sys_xsi_stack_overflow_heuristic=yes],
@@ -131,7 +216,8 @@ AC_DEFUN([AC_SYS_XSI_STACK_OVERFLOW_HEURISTIC],
        with the X/Open System Interface (XSI) option
        and is a standardized way to implement a SEGV-based stack
        overflow detection heuristic.])
-   fi])
+   fi
+  fi])
 
 
 AC_DEFUN([gl_PREREQ_C_STACK],
@@ -146,8 +232,6 @@ AC_DEFUN([gl_PREREQ_C_STACK],
 
    AC_CHECK_HEADERS_ONCE([unistd.h ucontext.h])
 
-   AC_CHECK_MEMBERS([struct sigaction.sa_sigaction], , , [#include <signal.h>])
-
    AC_CHECK_TYPES([stack_t], , , [#include <signal.h>])
 
    dnl c-stack does not need -lsigsegv if the system has XSI heuristics.