Application receive a SIGSEGV for stack growth failure

[Ravi Nallappan]

Hi,

I came across this rather unusual scenario and wonder why it behave as such:

OS: HPUX 11.11
Application : C
Compiler: HP C/HP-UX Compiler B.11.11.16

One of my application crashes with above error message, upon inspecting core, found that a function used up about 8MiB of stack size.

Here is simple program I wrote to reproduce the issue:

------test.c-------------
#include

struct _a_data {
int x ;
int y ;
int z ;
} ;
typedef struct _a_data *a_data_ptr ;

int func1( void ) {
int i = 0 ;
int num = 1 ;

while ( i < 3000000 ) {
a_data_ptr data[num] ;
int j ;
i++ ;
}
return 0 ;
}

int main( void ) {
printf("Yahoo1\n") ;
func1() ;
printf("Yahoo2\n") ;
return 0 ;
}
-------------------------

Compile and run as follow:
cc -g test2.c
gdb a.out
(gdb) break 28 # -> i++ ;
(gdb) run

Tracing $sp on every loop reveals that it used up additional 64 bytes per loop.

---------------------------
:
25 while ( i < 30000 ) {
(gdb) print $sp
$2 = 2139032080
(gdb) next
:
25 while ( i < 30000 ) {
(gdb) print $sp
$3 = 2139032144

---------------------------

And the stack size does not increase if
"a_data_ptr data[num] ;"
is removed, or use of other data types i.e "int x;" etc

Why such behavior? It is related to PA-RISC 2.0 feature or just a bug in compiler?

Thanks.

[Dennis Handly · Accepted solution]

This works fine on Integrity, where the default is C99.

>Why such behavior? or just a bug in compiler?

It's a bug in the C99 VLA implementation. It doesn't understand block scoping. You should move it out of the loop.

Please contact the Response Center to report this bug.

[Dennis Handly]

This also works fine on PA using "aCC -AC99".

[Ravi Nallappan]

Thanks Dennis, Thats answered my question.