On Jun 17, 2005, at 4:11 PM, Chad Leigh -- Shire.Net LLC wrote:
On Jun 17, 2005, at 2:49 PM, Earl Hood wrote:
On June 17, 2005 at 13:05, "Chad Leigh -- Shire.Net LLC" wrote:
So we see it does not get past the tmp=strdup(str); line when str =
chad . It seems to die in strdup as the cgi_output file ends
abruptly and we do not get any fprintf() from after the call
Could be memory allocation problem, or memory corruption. Did
you get a core file? Probably not because your coredumpsize limit
is probably 0.
Try running things under a debugger.
If you do not want to step through Apache code, you could modify
namazu.cgi to include a sleep call. This way you have time to
attach to the process with the debugger.
ok, except for when wrapped in fancy GUIs like in Apple's XCode, I am
a gdb neophyte
I set a break on nmz_codeconv_external which is where the error is
occuring
Breakpoint 2, nmz_codeconv_external (str=0xbffff620 "chad") at
codeconv.c:457
457 fprintf(stdout,"5 1 -- @%s(_at_)\n", str);fflush(stdout);
(gdb) n
454 nmz_codeconv_external (const char *str) {
(gdb) n
457 fprintf(stdout,"5 1 -- @%s(_at_)\n", str);fflush(stdout);
(gdb) n
459 tmp = strdup(str);
(gdb) s
Program received signal SIGSEGV, Segmentation fault.
0x400d26e5 in mallopt () from /lib/libc.so.6
(gdb)
OK, I took the definition of strdup from glibc source and added the
function directly into my codeconv.c so that strdup() would be my
version and not the glibc version
I step through it when the query is chad
---
Breakpoint 1, nmz_codeconv_external (str=0xbffff620 "chad") at
codeconv.c:472
472 fprintf(stdout,"5 1 -- @%s(_at_)\n", str);fflush(stdout);
(gdb) n
469 nmz_codeconv_external (const char *str) {
(gdb) n
472 fprintf(stdout,"5 1 -- @%s(_at_)\n", str);fflush(stdout);
(gdb) n
474 tmp = strdup(str);
(gdb) s
strdup (s=0xbffff620 "chad") at codeconv.c:94
94 size_t len = strlen (s) + 1;
(gdb) n
95 void *new = malloc (len);
(gdb) p len
$1 = 5
(gdb) p new
$2 = (void *) 0x4
(gdb) n
Program received signal SIGSEGV, Segmentation fault.
0x400d26e5 in mallopt () from /lib/libc.so.6
---
and when it is paul -- both 4 letter strings that should malloc
exactly the same.
---
Breakpoint 1, nmz_codeconv_external (
str=0x8061498 "<!DOCTYPE HTML PUBLIC \"-//W3C//DTD HTML 4.01//EN
\"\n \"http://www.w3.org/TR/html4/strict.dtd\";>\n<html>\n<head>
\n<!-- LINK-REV-MADE -->\n<link rev=made href=
\"mailto:webmaster(_at_)utah(_dot_)object(_dot_)com\">\n<!-- LIN"...)
at codeconv.c:472
472 fprintf(stdout,"5 1 -- @%s(_at_)\n", str);fflush(stdout);
(gdb) c
Continuing.
Breakpoint 1, nmz_codeconv_external (str=0xbffff620 "paul") at
codeconv.c:472
472 fprintf(stdout,"5 1 -- @%s(_at_)\n", str);fflush(stdout);
(gdb) n
469 nmz_codeconv_external (const char *str) {
(gdb) n
472 fprintf(stdout,"5 1 -- @%s(_at_)\n", str);fflush(stdout);
(gdb) n
474 tmp = strdup(str);
(gdb) s
strdup (s=0xbffff620 "paul") at codeconv.c:94
94 size_t len = strlen (s) + 1;
(gdb) n
95 void *new = malloc (len);
(gdb) p len
$1 = 5
(gdb) n
97 if (new == NULL)
(gdb) p new
$2 = (void *) 0x805f038
(gdb)
----
The malloc(5) fails every time the query is chad but never fails when
it is paul. It is exactly the same call and if a resource was being
exhausted malloc would return an error, and not segv. malloc()
should behave the same in both cases since it is the same call ==
malloc(5)
unless the malloc memory maps were previously corrupted by namazu or
some other code...
Still investigating
thanks
best
Chad
It always happens in the same place when str = chad but not when it
is paul or chad* or other things. This is mighty suspicious to me.
I guess it is off to find the source for glibc (as this is a gentoo
system) and look at strdup
no other system or program on this machine is having problems
including much more resource intensive cgi (assumed) under the same
username so I think namazu is screwing up the malloc/mallopt maps or
something
We'll see I guess
Chad
--ewh
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---
Chad Leigh -- Shire.Net LLC
Your Web App and Email hosting provider
chad(_at_)shire(_dot_)net
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---
Chad Leigh -- Shire.Net LLC
Your Web App and Email hosting provider
chad(_at_)shire(_dot_)net
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Namazu-users-en(_at_)namazu(_dot_)org
http://www.namazu.org/cgi-bin/mailman/listinfo/namazu-users-en