Re: [Gluster-devel] glusterd crashes when synctask is used in conjunction with inner functions.

[Krishnan Parthasarathi]

I tried the experiment you had suggested. The following are the 
changes I made to 'inner' function to take a single integer arg.
On compiling (gcc inner.c) and running, I didn't see any crash :(

--- inner.c     2012-10-09 00:06:53.799244495 +0530
+++ inner.c1    2012-10-09 00:06:34.173211036 +0530
@@ -1,6 +1,6 @@
 #include <stdio.h>
 
-typedef void print_fn (void);
+typedef void print_fn (int);
 
 print_fn *my_print_fn;
 
@@ -10,14 +10,14 @@
         int outer_val = 0x5678;
 
         void
-        inner (void)
+        inner (int a)
         {
-                printf("in inner function, result = 0x%x\n",outer_val);
+                printf("in inner function, result = 0x%x:%x\n",outer_val, a);
         }
 
 
         printf("in outer function\n");
-        inner();
+        inner(outer_val);
         my_print_fn = &inner;
 }
 
@@ -36,7 +36,7 @@
         if (argc > 1) {
                 rewrite_stack();
         }
-        (*my_print_fn)();
+        (*my_print_fn)(0x42);
         return 0;
 }
 


----- Original Message -----
> From: "Jeff Darcy" <address@hidden>
> To: address@hidden
> Sent: Monday, October 8, 2012 11:31:33 PM
> Subject: Re: [Gluster-devel] glusterd crashes when synctask is used in 
> conjunction with inner functions.
> 
> OK, I couldn't resist.  I've attached an inner-function test program
> which
> weakly confirms my theory.  If you run it with no arguments, the
> inner function
> works.  If you run it with arguments, this causes the stack to be
> reused and
> that seems to include the "thunk" I mentioned.  The result is a jump
> into
> nowhere, followed by SIGSEGV or SIGILL (oddly I've seen both).  If it
> fails in
> the outer-function-return case, I'll bet it fails with ucontext
> trickery too.
> 
> http://gcc.gnu.org/onlinedocs/gcc/Nested-Functions.html
> http://stackoverflow.com/questions/2929281/are-nested-functions-a-bad-thing-in-gcc
> 
> 
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